Fab at Home

This document is copyright under the BSD Documentation License:Copyright c©2007 Evan Malone. All rights reserved.Redistribution and use in source and ’compiled’ forms (SGML, HTML, PDF,

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THIS DOCUMENTATION IS PROVIDED BY Evan Malone ”AS IS” AND ANYEXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR APARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL Evan Mal-one BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EX-EMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIM-ITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSSOF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVERCAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)ARISING IN ANY WAY OUT OF THE USE OF THIS DOCUMENTATION, EVENIF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Contents

1 Overview 11.1 Introduction to the Fab@Home project . . . . . . . . . . . . . . . . . 11.2 Learning from the history of the computer revolution . . . . . . . . . 21.3 Goal of this project . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.5 Requirements Development Document . . . . . . . . . . . . . . . . . 4

2 Frequently Asked Questions 92.1 Can I buy a complete kit, or even a fully assembled machine? . . . . 92.2 What is the difference between a “Clear Unit” or “Colored Unit” and

“Complete Kit” on the Koba Industries website? . . . . . . . . . . . . 92.3 Where can I go to discuss my ideas about Fab@Home or fabbers? . . 92.4 How do I join the Fab@Home project or contribute to the Wiki? . . . 102.5 How do I edit the Fab@Home wiki? . . . . . . . . . . . . . . . . . . . 102.6 How much does a Model 1 cost? . . . . . . . . . . . . . . . . . . . . . 102.7 How large is a Fab@Home? . . . . . . . . . . . . . . . . . . . . . . . . 102.8 How long does it take to build a Model 1? . . . . . . . . . . . . . . . 112.9 What materials can be used with a Model 1? . . . . . . . . . . . . . . 112.10 How large an object can the Model 1 build? . . . . . . . . . . . . . . 112.11 How accurately can the Model 1 build an object? . . . . . . . . . . . 112.12 How do I tell the Model 1 what I want to build? . . . . . . . . . . . . 122.13 Can I use a Model 1 to build objects as part of my business? . . . . . 122.14 How does a Model 1 compare to a commercial RP machine? . . . . . 122.15 Can the Model 1 perform CNC milling? . . . . . . . . . . . . . . . . 132.16 If everything is open-source, where is the source code? . . . . . . . . 132.17 How does Fab@Home differ from RepRap? . . . . . . . . . . . . . . . 132.18 Where can I find a high-resolution photo of Fab@Home? . . . . . . . 142.19 Where can I learn more about the Model 1? . . . . . . . . . . . . . . 142.20 What does “SFF” mean? . . . . . . . . . . . . . . . . . . . . . . . . . 142.21 Still Have a Question? . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3 Gallery of Projects 153.1 Flashlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.1.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.1.2 Video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

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3.2 Frosting as Support Material . . . . . . . . . . . . . . . . . . . . . . . 18

3.2.1 Silicone Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.2.2 Trapezoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.2.3 Bouncy Ball/Sphere . . . . . . . . . . . . . . . . . . . . . . . 21

3.3 Epoxy Propeller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.3.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.3.2 Video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.4 Lego Car Tire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.4.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.5 House of Cheese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.5.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.5.2 Other Cheesy Images . . . . . . . . . . . . . . . . . . . . . . . 26

3.6 Silicone Watchband with Embedded Watch . . . . . . . . . . . . . . . 26

3.6.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.6.2 Video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.7 Frosting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.7.1 Crayola Cake Icing . . . . . . . . . . . . . . . . . . . . . . . . 28

3.7.2 Betty Crocker Easy Squeeze Frosting . . . . . . . . . . . . . . 28

3.8 Box in Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.8.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.9 Chocolate Structures (edible) . . . . . . . . . . . . . . . . . . . . . . 30

3.9.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.9.2 Video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.10 Silicone Squeeze Bulb . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.10.1 Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4 Links 35

4.1 Fab@Home in the Media . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.2 General audience (popular) papers and articles . . . . . . . . . . . . . 36

4.3 Reference and related web sites . . . . . . . . . . . . . . . . . . . . . 36

4.4 Commercial SFF/RP Systems and Contract Services . . . . . . . . . 36

5 Model 1 Overview 37

5.1 Buy a Model 1 Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.2 Five steps to get you going . . . . . . . . . . . . . . . . . . . . . . . . 37

5.3 Overall Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.4 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.5 Positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

5.6 Material Deposition Tool . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.7 Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.8 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

5.9 Building a Model 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

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6 Background Material 496.1 Stepper motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

6.1.1 Fundamentals of Operation . . . . . . . . . . . . . . . . . . . 506.1.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

6.2 Haydon Switch and Instrument Co.: Leadscrews . . . . . . . . . . . . 546.3 HSI 35000 Series: Size 14 Linear Actuators . . . . . . . . . . . . . . . 576.4 HSI 28000 Series: Size 11 Linear Actuators . . . . . . . . . . . . . . . 636.5 Deposition Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

6.5.1 Syringe Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . 686.5.2 Ink-jet Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . 706.5.3 Fountain Pen Tools . . . . . . . . . . . . . . . . . . . . . . . . 71

6.6 Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736.6.1 Embedded design . . . . . . . . . . . . . . . . . . . . . . . . . 746.6.2 Higher Integration . . . . . . . . . . . . . . . . . . . . . . . . 746.6.3 Large Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . 756.6.4 Programming Environments . . . . . . . . . . . . . . . . . . . 766.6.5 Interrupt Latency . . . . . . . . . . . . . . . . . . . . . . . . . 776.6.6 Development platforms for hobbyists . . . . . . . . . . . . . . 776.6.7 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

6.7 Universal Serial Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . 806.7.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816.7.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816.7.3 Host controllers . . . . . . . . . . . . . . . . . . . . . . . . . . 836.7.4 Device classes . . . . . . . . . . . . . . . . . . . . . . . . . . . 836.7.5 USB signaling . . . . . . . . . . . . . . . . . . . . . . . . . . . 856.7.6 USB connectors . . . . . . . . . . . . . . . . . . . . . . . . . . 856.7.7 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 886.7.8 USB compared to FireWire . . . . . . . . . . . . . . . . . . . 896.7.9 Version history . . . . . . . . . . . . . . . . . . . . . . . . . . 916.7.10 Related technologies . . . . . . . . . . . . . . . . . . . . . . . 926.7.11 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 936.7.12 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

6.8 STL (file format) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946.8.1 ASCII STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946.8.2 Binary STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 946.8.3 Colour in Binary STL . . . . . . . . . . . . . . . . . . . . . . 956.8.4 The Facet Normal . . . . . . . . . . . . . . . . . . . . . . . . 966.8.5 History of use . . . . . . . . . . . . . . . . . . . . . . . . . . . 966.8.6 Use in other fields. . . . . . . . . . . . . . . . . . . . . . . . . 976.8.7 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 976.8.8 External links . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

6.9 Xylotex: Automation, Motion Control & Robotics Products . . . . . 986.10 Firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

6.10.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1006.10.2 Origins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

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6.10.3 Evolved firmware uses . . . . . . . . . . . . . . . . . . . . . . 1016.10.4 Firmware and device drivers . . . . . . . . . . . . . . . . . . . 1016.10.5 Firmware support challenges in PCs . . . . . . . . . . . . . . . 1016.10.6 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026.10.7 See also . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1026.10.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

6.11 NXP Semiconductors Corp: LPC2148 Microcontroller . . . . . . . . . 1036.11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1036.11.2 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 104

7 Assembly Tools 1077.1 Assembly Tools for Model 1 . . . . . . . . . . . . . . . . . . . . . . . 1077.2 Vendors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

8 Styling 1098.1 Colors of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098.2 Etched Logos and Images . . . . . . . . . . . . . . . . . . . . . . . . 1108.3 Parts with Styled Shapes . . . . . . . . . . . . . . . . . . . . . . . . . 1108.4 Show your Style . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

9 Model 1 Bill of Materials 1139.1 Bill of Materials Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . 113

9.1.1 Current Version . . . . . . . . . . . . . . . . . . . . . . . . . . 1139.1.2 Legacy Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 114

9.2 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1149.3 Acrylic Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

9.3.1 Offset by 0.0055” for 35W Epilog Helix Laser Engraver . . . . 1219.3.2 Offset by 0.0000” (nominal size) for Waterjet cutting . . . . . 1229.3.3 Offset by 0.0035” for 85W Laser Cutter (Koba Industries) . . 122

9.4 Vendors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1239.4.1 Preferred Vendors (tested) . . . . . . . . . . . . . . . . . . . . 1239.4.2 Alternative Vendors (untested) . . . . . . . . . . . . . . . . . 125

10 Model 1 Cables 12710.1 Power Supply Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . 12710.2 Cable Extensions for HSI Motors . . . . . . . . . . . . . . . . . . . . 12810.3 Cables for Limit Switches . . . . . . . . . . . . . . . . . . . . . . . . 12910.4 Ribbon Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13010.5 Amplifier Enable Cable . . . . . . . . . . . . . . . . . . . . . . . . . . 13110.6 Bundling and Routing the Cables . . . . . . . . . . . . . . . . . . . . 133

11 Assembly Tips 13711.1 Threaded Inserts for Thermoplastics . . . . . . . . . . . . . . . . . . 13711.2 Stripping Cable and Wire . . . . . . . . . . . . . . . . . . . . . . . . 14011.3 Tinning Stripped Conductors . . . . . . . . . . . . . . . . . . . . . . 141

CONTENTS v

11.4 Soldering Motor Cable Extensions . . . . . . . . . . . . . . . . . . . . 141

11.5 Making IDC Ribbon Cable Connectors . . . . . . . . . . . . . . . . . 144

11.6 Making Limit Switch Connectors . . . . . . . . . . . . . . . . . . . . 147

11.7 Using Protective Braiding for Cables . . . . . . . . . . . . . . . . . . 152

11.8 General Soldering/Desoldering Methods . . . . . . . . . . . . . . . . 153

11.9 Soldering Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

11.9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

11.9.2 Installing a component. . . . . . . . . . . . . . . . . . . . . . . 154

12 Model 1 Base Assembly 157

13 Model 1 XY-Carriage Assembly 179

13.1 Parts Needed for Building XY Carriage . . . . . . . . . . . . . . . . . 179

13.2 Assembly Instructions for XY Carriage . . . . . . . . . . . . . . . . . 181

14 Model 1 Z-Carriage Assembly 225

14.1 Parts Needed for Building Z Carriage . . . . . . . . . . . . . . . . . . 225

14.2 Assembly Instructions for Z Carriage . . . . . . . . . . . . . . . . . . 226

15 Model 1 1-Syringe Tool 247

15.1 Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

15.2 Acrylic Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

15.2.1 Offset by 0.0035” for 85W Laser Cutter (Koba Industries) . . 249

15.2.2 Layout DXF file . . . . . . . . . . . . . . . . . . . . . . . . . . 249

15.3 Solidworks Assembly Files . . . . . . . . . . . . . . . . . . . . . . . . 250

15.4 Part Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

15.5 Model 1 1-Syringe Tool Assembly Diagrams . . . . . . . . . . . . . . 251

15.6 Mounting the 1-Syringe Tool to the Model 1 Chassis . . . . . . . . . 259

15.7 Syringe Tool Dispensing Components . . . . . . . . . . . . . . . . . . 261

15.7.1 Parts list with pricing, vendor, part number . . . . . . . . . . 262

15.7.2 Preferred vendors . . . . . . . . . . . . . . . . . . . . . . . . . 262

15.8 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

15.8.1 Structural Materials . . . . . . . . . . . . . . . . . . . . . . . 263

15.8.2 Elastomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

15.8.3 Conductive inks . . . . . . . . . . . . . . . . . . . . . . . . . . 264

15.8.4 Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

15.8.5 Edible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

16 Model 1 2-Syringe Tool 279

16.1 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

16.2 Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

17 Model 1 Chassis Assembly 281

17.1 Model 1 Chassis Assembly Diagrams . . . . . . . . . . . . . . . . . . 283

vi CONTENTS

18 Model 1 Electronics Assembly 291

18.1 Constructing the Model 1 Electronics . . . . . . . . . . . . . . . . . . 292

18.2 Modify Xylotex Board for Limit Switches . . . . . . . . . . . . . . . . 292

18.3 Attach the Enable Cable to the Winford Board . . . . . . . . . . . . 294

18.4 Mounting the Boards . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

18.5 Electronics Picto-Schematic . . . . . . . . . . . . . . . . . . . . . . . 299

18.5.1 Visio Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 299

18.5.2 Cable Attachment Images . . . . . . . . . . . . . . . . . . . . 300

18.6 Electronics Pinouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

18.6.1 Current Version . . . . . . . . . . . . . . . . . . . . . . . . . . 302

19 Model 1 Firmware Installation 303

19.1 Firmware Object Code Downloads . . . . . . . . . . . . . . . . . . . . 30319.1.1 Current Version . . . . . . . . . . . . . . . . . . . . . . . . . . 303

19.1.2 Legacy Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 303

19.2 Programming your LPC-H2148 with Rowley Crossworks v1.6 . . . . . 304

19.3 Firmware Development Environment . . . . . . . . . . . . . . . . . . 305

19.3.1 Download Rowley CrossWorks for ARM . . . . . . . . . . . . 305

19.3.2 Download Chip Support Package for the LPC2000 Family . . 305

19.3.3 Install CrossWorks and Request Evaluation License . . . . . . 305

19.4 Programming your LPC-H2148 Microcontroller . . . . . . . . . . . . 307

19.5 JTAG Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

19.5.1 JTAG for Rowley Crossworks . . . . . . . . . . . . . . . . . . 312

19.5.2 JTAG for ARM GCC Toolchain . . . . . . . . . . . . . . . . . 312

19.6 Rowley Crossworks for ARM . . . . . . . . . . . . . . . . . . . . . . . 313

19.7 Olimex JTAG Programmer (from Sparkfun Electronics) . . . . . . . . 314

19.8 Sparkfun Electronics: JTAG Programmer . . . . . . . . . . . . . . . . 315

20 Model 1 User Software Installation 319

20.1 Application Download . . . . . . . . . . . . . . . . . . . . . . . . . . 31920.1.1 Current Version . . . . . . . . . . . . . . . . . . . . . . . . . . 319

20.1.2 Beta Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

20.1.3 Legacy Version . . . . . . . . . . . . . . . . . . . . . . . . . . 320

20.2 Drivers Download . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

20.2.1 Current Version . . . . . . . . . . . . . . . . . . . . . . . . . . 320

20.2.2 Beta Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320

20.2.3 Legacy Version . . . . . . . . . . . . . . . . . . . . . . . . . . 320

20.3 Installation instructions . . . . . . . . . . . . . . . . . . . . . . . . . 320

21 Model 1 Commissioning 323

21.1 Mount the belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

21.2 Truing the XY Carriage . . . . . . . . . . . . . . . . . . . . . . . . . 325

21.3 Adjusting motor current . . . . . . . . . . . . . . . . . . . . . . . . . 327

21.4 Leveling the Z-Table . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

CONTENTS vii

22 Using Model 1 33322.1 Video Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33322.2 Quick Start User Guide . . . . . . . . . . . . . . . . . . . . . . . . . . 333

22.2.1 Step 1: Make Connection . . . . . . . . . . . . . . . . . . . . 33322.2.2 Step 2: Install Drivers . . . . . . . . . . . . . . . . . . . . . . 33422.2.3 Step 3: Run Application . . . . . . . . . . . . . . . . . . . . . 33422.2.4 Step 4: Initialize Hardware . . . . . . . . . . . . . . . . . . . . 33522.2.5 Step 5: Power On . . . . . . . . . . . . . . . . . . . . . . . . . 33622.2.6 Step 6: Verify Motion . . . . . . . . . . . . . . . . . . . . . . 33622.2.7 Step 7: Adjust Motor Current . . . . . . . . . . . . . . . . . . 33722.2.8 Step 8: Define Tool/Material . . . . . . . . . . . . . . . . . . 33722.2.9 Step 9:Load and Manipulate STL File(s) . . . . . . . . . . . . 33922.2.10Step 10: Assign Properties to Part Geometry . . . . . . . . . 34022.2.11Step 11: Inserting/Removing Syringes and Changing Materials 34022.2.12Step 12: Cover Build Surface . . . . . . . . . . . . . . . . . . 34222.2.13Step 13: Set Positions . . . . . . . . . . . . . . . . . . . . . . 34222.2.14Step 14: Plan Process . . . . . . . . . . . . . . . . . . . . . . 34322.2.15Step 15: Verify Material Flow / Flush and Wipe the Nozzle . 34322.2.16Step 16: Execute Process . . . . . . . . . . . . . . . . . . . . . 34422.2.17Step 17: Power Off . . . . . . . . . . . . . . . . . . . . . . . . 344

22.3 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34422.3.1 Application runs, but hardware is not responsive at all . . . . 34422.3.2 Software stops working . . . . . . . . . . . . . . . . . . . . . . 34522.3.3 Other questions . . . . . . . . . . . . . . . . . . . . . . . . . . 345

22.4 Materials Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34522.4.1 Loading a Syringe . . . . . . . . . . . . . . . . . . . . . . . . . 345

22.5 Design Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34622.5.1 Free CAD Programs . . . . . . . . . . . . . . . . . . . . . . . 34722.5.2 Commercial CAD Programs . . . . . . . . . . . . . . . . . . . 34822.5.3 Misc Programs . . . . . . . . . . . . . . . . . . . . . . . . . . 348

22.6 Design Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34922.6.1 Test files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34922.6.2 Simple parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

0 CONTENTS

Chapter 1

Overview

1.1 Introduction to the Fab@Home project

Universal manufacturing embodied as today’s freeform fabrication systems has – likeuniversal computers – the potential to transform human society to a degree that fewcreations ever have. The ability to directly fabricate functional custom objects couldtransform the way we design, make, deliver and consume products. But not lessimportantly, rapid prototyping technology has the potential to redefine the designer.By eliminating many of the barriers of resource and skill that currently prevent ordi-nary inventors from realizing their own ideas, fabbers can “democratize innovation”[1,2,3]. Ubiquitous automated manufacturing can thus open the door to a new classof independent designers, a marketplace of printable blueprints, and a new economyof custom products. Just like the Internet and MP3’s have freed musical talent fromcontrol of big labels, so can widespread RP (Rapid Prototyping) divorce technologicalinnovation from the control of big corporations.

Despite the formidable potential of rapid prototyping technology, its acceptanceover the last two decades has remained disappointingly slow [4]. At present SFF(Solid Freeform Fabrication) systems remain very expensive and complex, focused onproduction of mechanical parts, and used primarily by corporate engineers, designers,and architects for prototyping and visualization. These factors are linked in a viciouscycle which slows the development of the technology: Niche applications imply asmall demand for machines, while small demand for machines keeps the machinescostly and complex, limiting them to niche applications. Alternatively, if one couldprovide either a large market for SFF machines and products or a simple and cheapSFF machine with which end users could invent products and applications, then thissame feedback coupling could instead drive a rapid expansion in SFF technology andapplications.

1

2 CHAPTER 1. OVERVIEW

1.2 Learning from the history of the computer rev-

olution

Early home computers trying to break intohome market. (a) The Honeywell KitchenComputer cost $7000 and targeted thecooking as the “killer app;” (b, c) Thegeneral purpose Altair 8800, credited asstarting the home computer revolution,came as a $400 kit [7].

In attempt to break the vicious cycle of expensive equipment and niche applica-tions, there are many lessons to be learned from the rise and growth of an equivalentlyuniversal technology: The computer. The parallels between universal computationtechnology and universal manufacturing technologies are astounding. Though the uni-versal computer in its modern architecture was realized in the 40’s [6], two decadespassed before it reached any significant commercial acceptance. Early inventors them-selves could not foresee its huge potential, famously anticipating a need “for as manyas five or six machines in the US” [6]. The early commercial mainframes of the 1960swere used mostly for niche applications such as payroll and military calculations. Liketoday’s rapid prototyping machines, these early mainframes cost tens and hundredsof thousands of dollars, required hours to complete a single job, had the size of a largerefrigerator and required trained technicians to operate and maintain.

Though it was clear to early manufacturers that the home market offered greatpotential, it was unclear how to successfully capture that market. Early attemptsof the computer industry to break into the home market through niche “killer apps”failed miserably: Some brands targeted niche domains such as Honeywell’s “kitchenComputer” geared towards recipes (Figure a). Its high cost and narrow applicationprevented it from achieving success. Though several other home computers cameout in the early 1970’s [8], the MITS Altair 8800 (Figure b,c) is generally credited assparking the home computer revolution. Designed and sold through Popular Electron-ics as a $400 kit ($2015 in 2005 dollars), the Alltair 8800 broke the chicken-and-eggcycle: Hobbyists and experts could now afford to dabble with computers, developand exchange software and numerous hardware accessory projects. The availabilityof computers made it worthwhile to write software, and the availability of softwaremade it worthwhile to buy computers. Computer history had entered its exponentialgrowth era.

Based on this history, it seems reasonable to imagine a low-cost multi-materialSFF system in one’s home, which could produce objects or even complete integrateddevices from designs which are shared or purchased online [3]. Should such systemsbecome as available as personal computers or printers are today, the invention and

1.3. GOAL OF THIS PROJECT 3

personalization of small devices could become as ubiquitous as music sharing is today.MIT’s FabLab project [1] provides ample evidence that providing people with auto-mated fabrication tools serves as an innovation catalyst; ordinary folk, with seeminglyno technical background quickly learn to exploit these tools to design and realize newinventions. The only thing now missing is the low cost, hackable rapid prototyperkit.

1.3 Goal of this project

Inspired by this history, the goal of this project is to offer an open-source, low-cost,personal SFF system kit, which we call “Fab@Home”. The aim of this project is to putSFF technology into the hands of those same curious, inventive, and entrepreneurialcitizens. In addition, through the Wiki web site (http://www.fabathome.org) wehope to inspire users of Fab@Home to exchange their ideas for applications and theirimprovements to the hardware and software with us and each other. Several machinesare already in use.

1.4 Bibliography

1. Burns M., (1995) The Freedom to Create, in: Technology Management, Volume1, Number 4.http://www.ennex.com/˜fabbers/publish/199407-MB-FreedomCreate.asp

2. Gershenfeld N., (2005) FAB: The Coming Revolution on Your Desktop: FromPersonal Computers to Personal Fabrication, Basic Books.http://cba.mit.edu/projects/fablab/

3. Lipson H. (2005) “Homemade: The future of Functional Rapid Prototyping,”IEEE Spectrum, feature article, May 2005, pp. 24-31.http://www.mae.cornell.edu/ccsl/papers/Spectrum05 Lipson.pdf

4. Bowyer A., RepRap: The Replicating Rapid-Prototyper, http://reprap.org

5. Wohlers T., (2006), Rapid Prototyping & Manufacturing State of the Industry,Wohlers Assoc. http://www.wohlersassociates.com/

6. Ceruzzi P.E., (2000) A History of Modern Computing, The MIT Press

7. Klein E.S., Vintage Machines,http://www.vintage-computer.com/altair8800.shtml

8. Blinkenlights Archaeological Institute, http://www.blinkenlights.com/pc.shtml


1.5 Requirements Development Document

This document is intended to preliminarily establish definitions, stakeholders, context,and scope for the full Fab@Home Project. It is intended that this document will serveas a basis for the development of a full Project Requirements Document.Project Description: The Fab@Home Project has been created to design, develop,and publish software for, hardware designs of, and knowledge related to low-cost,open-source, “fabbers.” The project contains multiple components:

1. Overall System

(a) The Fab@Home Model 1 Fabber Project

i. Hardware

ii. Electronics

A. Electric Motors

B. Circuit boards

iii. Firmware

iv. Software

A. Application

B. Drivers

v. Documentation

A. Assembly instructions

B. Operation instructions

C. Design documents

D. Code documentation

E. Examples of use

F. Parameter files

(b) The Fab@Home website

(c) Open-source System Architecture for Future Fabbers

2. Definitions:

(a) Fabber: a fabber is a machine which constructs (fabricates) objects de-scribed by feasible models by depositing, assembling, condensing, reacting,and/or solidifying one or more materials under computer control. Alsoknown as a 3D printer or rapid prototypers.

(b) Production platform: a device capable of translating a production headin 3 dimensions, typically using a Cartesian or cylindrical coordinate sys-tems.

(c) Production Head: device mountable on a 3D production platform whichperforms additive or subtractive action using particular tools, media, orprocesses.

1.5. REQUIREMENTS DEVELOPMENT DOCUMENT 5

(d) Feasible model: a feasible model is a description of the object which theuser desires to have the fabber build, and which the fabber is capable ofbuilding.

(e) Open-source: the technical documentation required to recreate the soft-ware application, hardware, or other results, is made available to the gen-eral public without licensing restrictions that limit use, modification, orredistribution

3. Systems Engineering References:

(a) Engineering Complex Systems with Models and Objects, Oliver, Kelliher,Keegan. http://www.fabathome.org/wiki/uploads/8/8a/EngComplexSys-OKK.pdf

(b) IEEE Standard on Systems Engineering Process.http://www.fabathome.org/wiki/uploads/4/4b/IEEE1220-1998.pdf

(c) Vitech Inc. Document on Standard Diagrams for Systems Engineering Pro-cess. http://www.fabathome.org/wiki/uploads/4/4f/CommonGraphicalRepresentations 2002.pdf

(d) OMG SysML Specification Document.http://www.fabathome.org/wiki/uploads/2/24/OMGSysML-FAS-06-05-04.pdf

4. Project Stakeholders

(a) Developers

i. Software: involved in design and development of software compo-nents for fabbers

ii. Hardware: involved in design and development of hardware compo-nents of fabbers

(b) Users: interested in using fabbers to produce objects or products

(c) Retailer of Kits/Built Machines: selling kits or fully assembled fabbers

(d) Cornell University: host institution for the Fab@Home project

(e) Open Source community: norms, rules, legality, best practices for opensource projects

(f) Other open source fabber projects

• RepRap project: first open-source fabber project, competition/col-laboration, citation http://www.reprap.org

(g) US government: patent enforcement, other legality, export rules

(h) Foreign governments: importation rules

(i) Manufacturers: of commercial, proprietary RP machines

5. Originating Requirements


(a) The project shall develop fabber systems which shall

i. be easy to build

ii. be easy to operate

A. have well-written user documentation

iii. be easy to modify

iv. be inexpensive to build

v. be inexpensive to operate

vi. be compact

vii. produce little waste

viii. accept product description data (a model or design) from clients

A. clients may be humans

B. clients may be software

ix. assist the client in developing a feasible model

x. accurately fabricate any feasible model

xi. rapidly fabricate any feasible model

xii. automatically fabricate any feasible model

(b) The project shall provide open-source documentation of all aspects of itsfabber systems

i. Distributed documentation shall be sufficient to allow non-expert hob-byists to construct and operate their own fabbers

6. Interfaces

(a) Objective: Having a common hardware and software interface for printheads will allow the easy development and integration of a wide varietyof print heads. Includes hardware (physical mounting, electrical connec-tion, maximum/required dimensions) and software (required class inter-faces, functions)

(b) Hardware

i. System shall have well-defined interface for mounting print heads toproduction platform.

ii. System shall have well-defined electrical interface for powering andcontrolling print heads

(c) Software

i. System shall have well-defined software interface for print head control

7. Print heads

(a) Types

i. Additive

A. Syringe-based

1.5. REQUIREMENTS DEVELOPMENT DOCUMENT 7

• silicone

• Solder/soldering iron

• chocolate

• ice (rapid cooling tip, for making ice sculptures)

• ceramics

• wax (for making candles)

ii. Subtractive

A. Dremel-type

• carving

• polishing

• sanding

• others

iii. Combination/Miscellaneous

A. Laser

• Diode laser, liquid laser, etc.

• Enables 3D laser cutter

B. Heat gun

• I saw something using a heat gun to toast bread, making im-ages. . .

(b) Separate print tool from storage tool

i. Desirable to optionally have print material storage away from printhead. Material storage cartridge mounted to fixed point, connected toprint head which dispenses material

8. Miscellaneous list of thoughts:

(a) Possible Application Development Tools/Libraries:

i. Boost C++ libraries: dual license.http://www.boost-consulting.com/index.html

ii. CGAL computational geometry library: dual license.http://www.cgal.org/

iii. Qt GUI library: dual license. http://doc.trolltech.com/3.3/index.html

iv. OpenGL: free, open source. http://www.opengl.org

(b) Possible Embedded Development Tools/Libraries/OSs (for ARM):

i. FreeRTOS: open source embedded real-time kernel.http://www.freertos.org/

ii. Micrium uC/OS-II embedded real-time operating system:dual license. http://www.micrium.com

iii. GNUARM toolchain: http://www.gnuarm.org


(c) Possibly consider avoiding the word “fabber”, which seems ambiguous andinformal. Ok when used in proper noun (e.g Fab@Home), but might bebetter to use a more self-explanatory name

i. 3D production platform

ii. 3D printer

iii. Rapid Prototyper

(d) Microfabber concept

i. Use standard ATX computer case as framework for small fabber

A. Benefits

• Low cost of case

• Standard mounting holes

• Able to mount material storage cartridges and logic/power boardsin drive bays

• Built-in power supply w/multiple voltages

• Easily transportable, stronger frame than acrylic

B. Drawbacks

• Mounting holes may not be in ideal locations

• Limited maximum size of fabricated object

• May not be feasible/practical

(e) Improve electronics

i. Design custom circuit board for motor control electronics and proces-sor

A. More reliable operation

B. Cheaper

C. Use lower-cost motors

• Issues with HSI motor orders

• High cost for motors in low quantities (>10× markup)

• Investigate tradeoffs between servo & stepper motors

Chapter 2

Frequently Asked Questions

2.1 Can I buy a complete kit, or even a fully as-

sembled machine?

While you cannot yet order a fully assembled machine, you can now buy a com-plete kit from Koba Industries of Albuquerque, NM, USA. Koba can shipinternationally as well!!!!

You still need to build the machine yourself, and you can still buy the parts onyour own. Remember, everything in Fab@Home is free and open-source under theBSD License.

2.2 What is the difference between a “Clear Unit”

or “Colored Unit” and “Complete Kit” on the

Koba Industries website?

The “Clear Unit” and the “Colored Unit” are only the acrylic parts, and are not acomplete kit of parts for a Model 1. If you purchase either of these, you will still needto order the other components listed in the Model 1 Bill of Materials in order to builda Model 1. At present, obtaining the parts for a Model 1 will cost $2300 if you buythem from the vendors yourself, or a bit more if you order a complete kit from Koba(http://www.kobask8.com/servlet/Categories?category=Fab

2.3 Where can I go to discuss my ideas about

Fab@Home or fabbers?

There is a GoogleGroups forum for people interested in Fab@Home which simplifiesonline discussions - please visit:

• Fab@Home Forums on Google Groups

9

10 CHAPTER 2. FREQUENTLY ASKED QUESTIONS

2.4 How do I join the Fab@Home project or con-

tribute to the Wiki?

• If you have not already done so, make yourself an account:

– Click create account in the upper right hand corner of the page.

– Fill in the information and click “Create Account” or “By Email”

• Please also consider adding yourself to the Guest Book

• If you are building a fabber, please describe it on the Fabbers of the Worldpage.

2.5 How do I edit the Fab@Home wiki?

• Make sure you are logged in:

– If you see your username at the top right of the page, you are logged in

– Otherwise click Login at the top right corner of the page

• Click the “edit” tab (at the top) of the page you want to change

– Edit the “wiki text” to make the changes you would like to make

– click “Show Preview” at the bottom of the page to make sure that theresults are what you want

– If you are satisfied, click “Save Page” at the bottom of the page

Now everyone can see your contribution!For more details on editing “wiki text” and contributing, please see:

• Editing Help

• MediaWiki Editing Instructions (offsite)

2.6 How much does a Model 1 cost?

Buying all of the parts for a Model 1 currently costs about $2400. Interestingly, theAltair 8800 minicomputer kit, credited with starting the personal computer revolu-tion, cost $400 in 1970, or $2015 in 2005 dollars.

2.7 How large is a Fab@Home?

The Model 1 stands at 18.5” (47cm) wide, by 16” (40.6cm) deep, by roughly 18”(45.7cm) tall.

2.8. HOW LONG DOES IT TAKE TO BUILD A MODEL 1? 11

2.8 How long does it take to build a Model 1?

Once you have all of your parts and tools in hand, the Model 1 can be put togetherin an intense weekend of 18-24 work hours by someone with basic hobby skills (e.g.soldering). If you find that it takes you much more or less than this, please contactEvan.

2.9 What materials can be used with a Model 1?

The 1-Syringe Tool of a Model 1 is designed to work with almost any kind of liquid orpaste that you can imagine dispensing from a syringe. We have tried using householdsilicone rubber caulk, epoxy, cheese, chocolate (with a small heater attached to thesyringe tool), cake frosting, ceramic clay (when mixed with sufficient water), PlayDoh,gypsum plaster. This is merely a list of the materials we have had time to play with- many, many more materials are possible, and it is the intent of Fab@Home to makeit easy for you to try your own materials. A good material is soft/fluid enough topush through a syringe, but firm enough that it will “stack up”. See the Model 1User Manual for info on setting up a new material.

2.10 How large an object can the Model 1 build?

The build volume of the machine is roughly 8” cubed. The current record for thetallest object is a bit under 4”, but that was only limited by patience.

2.11 How accurately can the Model 1 build an ob-

ject?

The accuracy and repeatability depend upon the material you are working with (doesit flow?, does it change shape with time?), the time you have spent tuning the depo-sition parameters, and the the nozzle diameter, as well as on the positioning accuracyand repeatability of the machine. For a “good” material that does not flow, theX-Y (layer plane) resolution is roughly twice the diameter of the nozzle, and theZ (height) resolution is roughly equal to the nozzle diameter. In theory, this holdsuntil you approach the positioning resolution of the machine, which is roughly ±25micrometers. The accuracy and repeatability of the positioning system of the Model1 have not been measured. At a rough guess, without special attention paid to setup,the repeatability will be roughly ±100 micrometers.


2.12 How do I tell the Model 1 what I want to

build?

You need to provide the Model 1 with a 3D model of the object you would like tobuild. You can generate the model using either 3D design software or a 3D scanner.The Fab@Home Model 1 software reads STL (stereolithography) files, which you canexport from programs such as SolidWorks, Autodesk Inventor, CosmicBlobs, etc - seethe Design Tools section. Alternatively, a 3D scanner, such as David or NextEnginecan be used to scan objects to produce a model, which can then be converted into anSTL file that Fab@Home can build.

2.13 Can I use a Model 1 to build objects as part

of my business?

While we would be thrilled to see this happen, and all of the content of this websiteis free for commercial or hobby uses, the Model 1 will not be able to compete witha commercial RP system in terms of resolution, and the reliability of the Model 1for long-term use is not yet known. If your business would like to use a Model 1for producing very detailed parts, very frequently, we would have to recommend thatyou stick with outsourced RP service such as XPress3D or a commercial RP machine(if you can afford one). Fab@Home is helping to make RP/fabbing technology open-source, so that users can try their own materials, and improve the machine accordingto their needs, all for far less money than purchasing a commercial machine. If youare interested in helping to make Fab@Home competitive with commercial machines,or want to experiment with multiple-material RP, then please do build a Fab@Homemachine.

2.14 How does a Model 1 compare to a commercial

RP machine?

See “ Can I use...” above. Most commercial machines can build larger objects, faster,and with smoother surfaces and finer details. Several commercial machines also canbuild with materials such as ABS, Nylon, and polycarbonate - tough engineeringthermoplastics, although parts must be made entirely of one material, so you cannothave different portions of the same part made of different materials. Commercialmachines are 10 to 100 times as expensive as a Fab@Home, the materials are pro-prietary and expensive, and you typically cannot modify the machines, materals, orsoftware to suit your own needs. The Fab@Home Model 1 allows you to use yourown, low-cost materials, and to build objects that contain multiple materials. TheFab@Home Project is trying to popularize rapid prototyping/fabbing technology, tomake it open source, and to make it inexpensive, all to get as many people as possibleto use and experiment with fabbers. We believe that fabbing will be a revolutionary

2.15. CAN THE MODEL 1 PERFORM CNC MILLING? 13

technology, possibly as important in the future as computers are today, and thatintroducing the public to fabbers in a way which invites experimentation and im-provement is an essential part of realizing this revolutionary potential. Having saidthat, the Fab@Home Model 1 is targeted at experimentation and hobby use, and isprobably not ready for the demands of commercial application. Join the Fab@Homeproject, and help develop the future Fab@Home models!

2.15 Can the Model 1 perform CNC milling?

The Model 1 is not very rigid, since depositing material produces almost no lateralforce. To make the Model 1 into a mill would require building the chassis out of some-thing stiffer and stronger than acrylic. If milling is your real interest, then Fab@Homeis not your best starting point. Try http://www.cncci.com/resources/links.htm.

2.16 If everything is open-source, where is the source

code?

A Source Forge project has been set up to facilitate the open-source software devel-opment for Fab@Home, since they provide lots of nice tools for management. Theproject can be found at http://sourceforge.net/projects/fabathome. The applicationsource is there, and the firmware and USB driver code will be added as soon aspossible. Evan 19:20, 27 January 2007 (EST)

2.17 How does Fab@Home differ from RepRap?

There are two main differences. The first is that the RepRap is oriented toward self-replication - trying to make a machine that can make many of its own parts, whileFab@Home is aiming to get as many people as possible to play with/hack/improvefabbers. The second is that RepRap has a screw extrusion deposition tool that isdesigned for use with polycaprolactone plastic as the intended building material, whileFab@Home uses a syringe tool that allows you to use a wider variety of materials.

The RepRap requires a bit more technical proficiency and quite a bit more in termsof the tools you need. For instance, with RepRap, you need to build the circuit boardsand need metalworking machinery to make some of the parts, while Fab@Home is asnap-and-screw-together kit, with bit of soldering as the most challenging part. Ofcourse the RepRap is cheaper for this same reason.

The two projects have a lot to offer each other - you could easily mount thedeposition tool from one onto the other - e.g. polycaprolactone screw extruder onFab@Home or syringe tool on the RepRap Darwin.


2.18 Where can I find a high-resolution photo of

Fab@Home?

Several popular photos are available at the bottom of the home page of the website(http://fabathome.org/). Many of the other photos on this website are of high-resolution - see especially the Fabbers of the World, and Gallery of Ideas pages. Clickon the photo to go to the main page for that photo, where the photo size and a linkto the highest resolution version will be displayed.

2.19 Where can I learn more about the Model 1?

Please see Chapter 5 for a more detailed overview of the Model 1.

2.20 What does “SFF” mean?

SFF stands for Solid Freeform Fabrication - basically an umbrella term for 3-D print-ing, Rapid Prototyping, additive manufacturing, etc. - building things by having amachine deposit material under computer control. Some people prefer “Rapid Proto-typing”, but since we are trying to use it for more than just “prototyping”, I kind ofprefer “fabrication”, and since it isn’t really that fast, we usually ditch the “rapid”.Maybe “Additive” is better? 3-D printing is actually a trademark of Z-Corp., so Ishy away from that as well. See also Wikipedia definition and Castle Island RP/SFFreference site.

2.21 Still Have a Question?

If the information provided does not answer your question, please contact Evan Mal-one ([email protected]).

Chapter 3

Gallery of Projects

3.1 Flashlight

Recently, Dan Periard has been experimenting with printing electrical circuits withconductive silicone and conductive ink, while Evan Malone has been testing out epoxyas a structural material. Meanwhile, the Fab@Home Project has had the great honorof being included in an upcoming exhibition Plasticity - 100 years of making plasticsat the Science Museum London, starting May 22nd, 2007. We have put together aModel 1 for the museum to display, which will be added to their permanent collection,and also needed to provide a sample of the Model 1’s capabilities. Since this is forposterity, we racked our brains a bit, pulled out all of the stops, and came up with whatyou see below: an LED flashlight which combines printed silicone, printed conductivesilicone, printed epoxy, and cast epoxy materials; Dan’s printable electrical switchand flap-door inventions; an embedded LED (ultra-bright orange) as the light source;commercial AA batteries which can be dropped in via the back end; and a rugged,yet handsome and comfortable rubber over epoxy body. The whole thing was printedin 2 steps: Step 1 (˜8 hours) was to print the the entire body with embedded LED,conductive contacts, switch, and endcap, and Step 2 (˜30 minutes) was to link theendcap to the LED by printing and embedding a conductive silicone circuit. Wedeveloped a few neat techniques that allowed us to achieve all of this; we’ll try todocument these on the techniques page in the near future.

15

16 CHAPTER 3. GALLERY OF PROJECTS

3.1.1 Images

Just to prove it could be done, andto seize the Fabber of the Month ti-tle, Dan spent 7+ hours to make anenormous 100mm tall hexagonal sil-icone flashlight body as a prototype

After building the monster proto-type flashlight body, Dan tested outthe idea of laying the body on itsside and then printing the conduc-tive trace (silver-filled silicone) intoa groove he designed into the body

Here Dan is testing out embedding(covering over) the conductive traceto protect it and to improve the aes-thetics of the product

After the prototyping, we designeda complete “production” version.Here is the CAD model of that de-sign.

3.1. FLASHLIGHT 17

You can see the cast (poured) epoxy inbetween the inner and outer printed sil-icone walls of the body, and the channelleft for the conductive trace (at left)

A view of the end cap underway - therounded channel and hole are part ofthe electrical switch

Proof of the height - about 115mm tall- the Z-axis couldn’t move down anyfurther (note to designers of Model 2!)

The embedded trace technique beingused to connect the thumb switch onthe end cap (right) to the LED anode(embedded in the left-hand end)


A nice view of the LED embedded inprinted epoxy in the front end. Theflashlight has a very nice heft and feel -the silicone layers make a nice soft gripover the solid epoxy body

(Excuse the poor focus) It works! Once2 AA batteries are dropped in via theend cap, the flashlight can be turned onby pressing (and holding) the switch inthe end cap.

3.1.2 Video

Flashlight300X.wmv,(32MB .WMV);

A movie of the LED flashlight being printed and demonstrated, accelerated 300X(total elapsed time, 8h 8min):http://fabathome.org/wiki/uploads/1/1b/Flashlight300X.wmv.

3.2 Frosting as Support Material

Here we used normal frosting (same as below, albeit a different color) to act as asupport material for various silicone objects. By creating an individual part for eachmaterial, we could have the Fab@Home print the frosting first, then lay the siliconedown afterward.

3.2.1 Silicone Bridge

The first attempt at support materials: this is simply a silicone bridge sitting on topof a block of frosting.

3.2. FROSTING AS SUPPORT MATERIAL 19

The foundation to our bridge (noticethat the paths are quite a bit tighterthan the pictures below).

The first bridge: the silicone doesn’tstick real well to the frosting, so thebridge is pretty hideous.

A completed bridge on the left, and asecond bridge during construction.

Cool pattern on the bridge. I totallymeant to do that. . .

Breaking away the frosting (I let thesilicone harden overnight).

Some more breaking. . .


With most of the frosting cleaned out. It’s a bridge!

3.2.2 Trapezoid

Second attempt at supports - this involves building a silicone shape completely sup-ported by the frosting. Yes, this particular shape could have been printed upside-down, but it’s way cooler to do it this way.

First layer of silicone laid out on top ofthe frosting.

The nearly completed trapezoid. Itturned out much prettier than thebridge.

Breaking away the frosting. It’s a trapezoid!

3.2. FROSTING AS SUPPORT MATERIAL 21

3.2.3 Bouncy Ball/Sphere

Third, and most glorious, attempt - Printing a silicone sphere!

A look at the mold, roughly a dozenlayers in.

Mold, nearly completed.

Completed mold. Can see that thereare some stragglers in the bottom. . .

Initial silicon layering.

Mmmm. . . look at the frosting inte-grated directly into the silicone. Tasty!

Almost done. . .


Complete!Looks like a snow-cone. Maybe I couldshape the mold differently next time. . .

The sphere wasn’t exactly centeredwhen it started printing, so it pushedout one of the corners.

Ball out of mold (reusable mold, per-haps?).

Not quite a sphere, but pretty close. Breathtaking, isn’t it?

3.3 Epoxy Propeller

Here we used the Fab@Home to produce a silicone rubber mold for a 7.5” diameterpropeller suitable for an RC airplane or a rubber-band powered balsa plane. Wemanually filled the mold with epoxy while it was being fabbed so that overhangingparts of the mold would not cave in. The mold did not release cleanly from the epoxy,

3.3. EPOXY PROPELLER 23

and the propeller needed some manual clean up with a Dremel to remove adheringsilicone and some rough edges. In the end, the propeller really works, as can be seenin the video, where we tested it as a “hand powered helicopter” toy.

3.3.1 Images

The completed mold, in place on thebuild surface of one of our Model 1s.

The silicone propeller mold (black GESilicone II), completed, and partiallyfilled with epoxy

The mold, birds-eye-view - note thatthe build time of the mold was 5 hours.The mold could be made a closer fit tothe propeller to reduce build time.

The propeller right after removal fromthe mold before manual clean-up.


The propeller after being cleaned upand balanced; we used a Dremel with asmall grinding bit.

Edge view of the propeller, mounted ona balsa stick as a toy “helicopter”

3.3.2 Video

PropellerMovie.mpg, (35MB Hi-res);

A movie of Evan testing out the epoxy propeller as part of a toy Requires WindowsMedia Player 11: http://fabathome.org/wiki/uploads/2/2d/PropellerMovie.mpg.

3.4 Lego Car Tire

3.4.1 Images

Black silicone replica of a Lego tireCloseup of tire showing treads andspoked interior

3.5. HOUSE OF CHEESE 25

Lego tire mounted on lego hub and axle Lego tractor repaired with fabbed tire

3.5 House of Cheese

3.5.1 Images

A house, complete with car anddriveway, made of “edible” “spray-cheese”,deposited on a saltine cracker

A second view of the cheese house

A bird’s eye view of the cheese house


3.5.2 Other Cheesy Images

Test shape for “cheez-whiz” The cheese holds its shape pretty well.

A cheap knock-off of Cornell’s logo ona cracker

Printing on an object is a matter of eye-balling it: hence the guy on the right isa little off.

3.6 Silicone Watchband with Embedded Watch

3.6.1 Images

Image of CAD design of watch band

Screenshot of Fab@Home applicationwith watch band model

3.6. SILICONE WATCHBAND WITH EMBEDDED WATCH 27

Closeup of part about 2/3 done Wider view of part in machine

Finished part on build surface with em-bedded watch

The latest thing in fashion!

3.6.2 Video

• WatchbandDemoMovie.wmv, 28.5MB Movie of watchband fabrication:http:/fabathome.org/wiki/uploads/5/51/WatchbandDemoMovie.wmv


3.7 Frosting

3.7.1 Crayola Cake Icing

Images

A rectangular box made of Crayola Cake Icing

3.7.2 Betty Crocker Easy Squeeze Frosting

Easily the best-tasting bunch of models... Hopefully we can print a cookie, then bakeit, then frost it, all on the Fab@Home machine (minus the baking, I suppose).

Images

A frosting arrow through a red arrowheart under construction

Arrow through the heart - all edible!

3.8. BOX IN CYLINDER 29

3.8 Box in Cylinder

This demonstrates the multiple material capability of the Model 1, and a neat featureof “fabbing” - it is possible to make one object (in this case a brown box) completelyenclosed inside of another object (in this case a transparent cylinder). This would be


very difficult to make any other way.

3.8.1 Images

A brown silicone box completely en-closed in a clear silicone cylinder

A second view of the box inside thecylinder

3.9 Chocolate Structures (edible)

3.9.1 Images

High Resolution - smaller size: can fitto your palm or your finger tip

3.9. CHOCOLATE STRUCTURES (EDIBLE) 31

Getting rid of the air


A view of the heated syringe arrange-ment - just a thermostatically con-trolled flexible heater wrapped aroundthe syringe barrel, then covered withinsulation.

3.9.2 Video

Chocolate1.mpg, 2.1MB Movie of Printing a Chocolate Bar:http://fabathome.org/wiki/uploads/4/47/Chocolate1.mpg

Chocolate2.mpg, 5.2MB Movie of Printing a Chocolate Bar:http://fabathome.org/wiki/uploads/8/87/Chocolate2.mpg

Chocolate3.mpg, 7.2MB Movie of Printing a Chocolate Bar:http://fabathome.org/wiki/uploads/b/b0/Chocolate3.mpg

Chocolate4.mpg, 40.6 MB Movie of Printing a Chocolate Bar:http://fabathome.org/wiki/uploads/1/17/Chocolate4.mpg

3.10. SILICONE SQUEEZE BULB 33

3.10 Silicone Squeeze Bulb

3.10.1 Images

CAD model of a rubber squeeze bulb

Screenshot of Fab@Home

Home application with squeeze bulb model

Image of squeeze bulb at about layer 60of 337 layers

Image of squeeze bulb at about layer180 of 337 layers

Side view of squeeze bulb at about layer182 of 337 layers



Top view of squeeze bulb at about layer250 of 337 layers


SqueezeBulbDemoMovie.wmv, 16MB Movie of squeezebulb fabrication:http://fabathome.org/wiki/uploads/b/bb/SqueezeBulbDemoMovie.wmv.

Chapter 4

Links

4.1 Fab@Home in the Media

• Two television technology shows have recently visited the Fab@Home Labs at Cor-nell University to cover the project for upcoming episodes!

• The Science Museum, London, UK is including a Fab@Home Model 1 in an exhibitentitled ”Ingenious - centenary of plastics” commencing in May, 2007!

• The New York Times, April 5, 2007 (http://fabathome.org/wiki/uploads/7/73/NYTimes4-6-2007web.pdf)

• The Guardian, UK newspaper, March 29, 2007,(http://fabathome.org/wiki/uploads/8/81/TheGuardian3-29-2007.pdf)

• The Cornell University Daily Sun, March 7, 2007.(http://fabathome.org/wiki/uploads/6/67/CornellDailySun3-7-2007.pdf)

• Science Daily science blog picked up the Cornell Chronicle article, February 26,2007 (http://www.sciencedaily.com/releases/2007/02/070226213551.htm)

• The Cornell Chronicle newspaper, Cornell University, February 26, 2007.(http://fabathome.org/wiki/uploads/6/63/CornellChronicle2-26-2007.pdf)

• Newsweek International Print edition, February 5, 2007.(http://fabathome.org/wiki/uploads/8/8d/NewsweekInternational2-5-2007print.pdf)

• Newsweek International Web edition, February 5, 2007.(http://fabathome.org/wiki/uploads/7/77/NewsweekInternational2-5-2007web.pdf)

• Newsweek Russia, January 22, 2007.(http://fabathome.org/wiki/uploads/b/bd/NewsweekRussia1-22-2007.pdf)

• Technovelgy.com, January 11, 2007.(http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=895)

• Wired Magazine’s Beyond the Beyond Blog, January 11, 2007.(http://blog.wired.com/sterling/2007/01/spime watch fab.html)

• New Scientist Magazine’s NewScientistTech.com technology magazine, January 9,2007. (http://fabathome.org/wiki/uploads/1/14/NewScientistTech1-9-2007.pdf)

• Slashdot technology blog, January 9, 2007.(http://hardware.slashdot.org/article.pl?sid=07/01/09/2239206&from=rss)

• Hackaday technology hacker blog, December 8, 2006.

35

36 CHAPTER 4. LINKS

(http://www.hackaday.com/2006/12/08/fab-home/)• YouTube (http://www.youtube.com/watch?v=e26MBnnQEIE)

4.2 General audience (popular) papers and arti-

cles

1. Lipson H. (2005) ”Homemade: The future of Functional Rapid Prototyping”, IEEESpectrum, feature article, May 2005, pp. 24-31.(http://www.mae.cornell.edu/ccsl/papers/Spectrum05 Lipson.pdf)

2. Gershenfeld N., (2005) FAB: The Coming Revolution on Your Desktop: FromPersonal Computers to Personal Fabrication, Basic Books.

3. Burns M., (1995) The Freedom to Create, in Technology Management, Volume 1,Number 4. (http://www.ennex.com/ fabbers/publish/199407-MB-FreedomCreate.asp)

4. Ceruzzi P.E., (2000) A History of Modern Computing, The MIT Press5. McMains, S. (2005) ”Layered Manufacturing Technologies”, Comm. ACM, Volume

48, Number 6, pp 50-56.(http://portal.acm.org/citation.cfm?id=1064858&coll=ACM&dl=ACM&CFID=13415255&CFTOKEN=78174790)

4.3 Reference and related web sites1. Castle Island RP/SFF reference site (http://home.att.net/ castleisland/)2. MIT FabLab Project (http://cba.mit.edu/projects/fablab/)3. RepRap: The Replicating Rapid-Prototyper, Open Source Project, UK.

(http://reprap.org)4. Rapid Prototyping & Manufacturing State of the Industry, Wohlers Assoc.

(http://www.wohlersassociates.com/)5. Vintage Machines, Computer History Site .

(http://www.vintage-computer.com/altair8800.shtml)

4.4 Commercial SFF/RP Systems and Contract

Services

• Stratasys, Inc. of Eden Prairie, Minnesota. (http://www.stratasys.com)• Z-Corp of Burlington, Massachusetts. (http://www.zcorp.com)• 3D Systems, Inc. of Valencia, California. (http://www.3dsystems.com)• EOS GmbH of Munich, Germany. (http://www.eos-gmbh.de/)• Desktop Factory of Pasadena, California. (http://www.desktopfactory.com/)• Objet Geometries of Rehovot, Israel. (http://www.2objet.com/)• Dimension 3D (A division of Stratasys). (http://www.dimensionprinting.com/)• XPress3D Rapid Prototyping Services Quotations. (http://www.xpress3d.com/)

Chapter 5

Model 1 Overview

The Model 1 (Fig. 5.1) is the very first Fab@Home fabber design. It includes ev-erything necessary for basic, multimaterial desktop fabrication. It makes use of abasic ”syringe pump” material dispensing tool, with disposable syringes to enabledispensing of a wide variety of materials. It uses ”linear stepper motors” - steppermotors with lead screws attached - as the actuators, and has 4 axes of control - 1 forthe syringe tool plunger, 1 for the Z axis (the vertical motion of the table on whichparts are built), and 1 each for the X and Y axes to move the syringe tool along thepaths required to build up a part layer by layer. The Model 1 Electronics includea 4-axis amplifier for the 4 stepper motors, an LPC-H2148 ARM7 microcontrollerwith USB interface, limit switches to sense when the X, Y, and Z axes are at the endof their motion ranges, and some (passive) interface components (a breakout boardand cables). The cost of the materials required for the Model 1 is about US$2300before shipping, using the current known lowest cost vendors, and placing all of theorders yourself. It is now possible to order a full kit of parts from a single source, ata slightly higher price than if you place individual orders yourself. Please see below:

5.1 Buy a Model 1 Kit

If you would like to skip much of the do-it-yourself stuff, and just buy a kit (you’llstill need to do the assembly yourself) please visit Koba Industries new store:

• http://www.kobask8.com/servlet/Categories?category=Fab

5.2 Five steps to get you going

1. Choose and build a Fabber. Visit the catalog page to pick out the fabberthat you would like, and to find information about building your own fabber.You will need to either buy a kit from Koba Industries, or purchase the partsfor the fabber separately, and also some simple tools to build the machine with.We hope that in the near future maybe someone will also be willing to buildand sell assembled machines <if you are, edit this page>

37

38 CHAPTER 5. MODEL 1 OVERVIEW

Figure 5.1: A Fab@Home Model 1 Fabber

5.3. OVERALL DESIGN 39

2. Install the software. Download and install the software binaries (USB driverand Fab@Home software). Check that it talks to the printer and you are ableto manually jog the carriage. Later, you can download the source code, see howit works and improve it.

3. Select and buy some building materials. Visit the materials page to selectsome materials. Start with a simple material like playdough or 1-part silicone.Later you can move on to more sophisticated materials, cocktails, and multi-material assemblies.

4. Download an object to print. Visit the Design Library page and downloadthe model of an object to print. Import the model into your Fab@Home soft-ware. Start with something simple like a cube or a cone. Later you can exploremore complex structures.

5. Print the object. Load your deposition tool with material, and print theobject using the software.

Please consult the Frequently Asked Questions section when you have difficulties.If you solved any of these problems, please be sure to update the FAQ area with yoursolutions.

5.3 Overall Design

The Fab@Home Model 1 (Figure 5.2(a)) is a 3-axis Cartesian gantry positioningsystem driven by stepper motors attached to lead screws in a configuration called alinear stepper motor. Material deposition tools are modular, and the first tool wehave designed is a syringe-based extrusion tool which uses a linear stepper motorto control the syringe plunger position. The electronics of the current version of thesystem provide for 4 axes of bipolar stepper motor control at 24V, with 2 limit switchesper axis of positioning, plus an optional one limit switch for the remaining 3 axes. Thesoftware and firmware support up to 6 axes of control in their current incarnation.A microcontroller controls the positioning of the axes and is in bidirectional USBcommunications with the PC. An application running on the PC displays the real-time state of the machine numerically and graphically, and allows the user to manuallyposition the axes, import, assemble, and perform basic modifications to STL geometrydata, apply specific material properties to each STL, and to generate and execute toolpaths in order to fabricate objects comprising multiple materials.

One concern in developing our design has been that there probably exists a thresh-old of quality required in any new technology kit for hobbyists, below which the ex-citement of the new technology will be masked by the malfunctions, maintenanceproblems, and poor aesthetics. Users must have a sense of what the technology iscapable of before they can grasp how to modify it and apply it to their own purposes.Our first design has therefore focused more on ease of use, reliability, and aestheticsthan on minimizing cost.


Figure 5.2: The Fab@Home Model 1 Design. (a) 3D CAD model of an assembledModel 1; (b) An example of assembly instructions

We have tried to assume a modest availability of technical tools and skills forthe end user, and have tried to facilitate assembly by providing very detailed as-sembly documentation (Figure 5.2(b)). The builder needs to have a laptop or PCwith a USB port, and basic assembly tools including Allen keys, screwdrivers, scis-sors, pliers, and a soldering iron. Assembly consists of snapping together the acrylicstructure, inserting nuts and screws and threaded inserts, bolting together the posi-tioning system components and mounting them to the structure, making cables toconnect the microcontroller to the amplifier boards, and the motors to the amplifierboards, mounting the electronic boards to the chassis, and bundling and routing ofcables. Soldering and crimping of cables and connectors are the most challengingassembly tasks, but the project documentation is exhaustive, offering advice, imagesand reference websites for these and almost every other task. The user is expectedto have some patience as well: completely assembling a kit from parts to operationrequires roughly 18 hours of labor. Currently, the parts cost is estimated to be $2300,including the cost of having acrylic parts laser-cut, and not including shipping costs(remarkably, the Altair 8800 cost adjusted to 2005 dollars would be $2015!). Table5.1 summarizes the hardware parts and costs for the kit.

5.4 Structure

The structural components of our system are built from laser-cut acrylic sheet partsheld together with snap-fit joinery and simple “T-nut” style screw/nut fastening, inwhich a square or hex nut is inserted into a slot in one part, and a screw is threaded inthrough a hole in a perpendicular part. The tight manufacturing tolerances achievablewith laser cut acrylic enable us to produce good orthogonality and alignment in the

5.5. POSITIONING 41

Category # of Items / # of Types Materials CostMotors 4/4 $610.59Electronics 24/15 $367.78Bearings/Transmission 53/18 $662.52Fasteners/Hardware 360/23 $158.73Acrylic 5/2 $493.00Control Software 3/3 $0.00Totals 447/62 $2292.62

Table 5.1: Model 1 Fabber: Hardware and Cost summary.

machine base, increasing the ease of setup and reliability of the machine. Our firstthree units have been produced in-house with an Epilog Helix 35W laser engraver(Epilog, Inc.), cutting parts directly from SolidWorks (SolidWorks, Inc.) drawingfiles, which are in turn generated from a SolidWorks 3D CAD model of the completesystem. There are 33 acrylic sheet parts in the chassis, plus an additional 7 acrylicparts for the syringe tool. Currently, 5 sheets of 18-inch × 24-inch × 0.236-inchcast acrylic are used to produce the acrylic parts. Cutting the parts for an entiremachine requires three hours on our 35W laser cutter. We have arranged contractmanufacturing service (Koba Industries, Albuquerque, NM, USA) for these acrylicparts to simplify the purchasing process for end users, and costs for this service willdecrease as order volumes increase. An additional benefit to having the structuralparts laser-cut is that there is a large installed base of laser cutters/engravers in thesign making, and trophy and gift engraving industries. The custom nature of the workin these industries should make them amenable to kit builder’s approaching them tohave parts made. In addition, most laser-cutting equipment used in these industriesdoes not require specialized CAM software – they operate from an application printerdriver, so almost any image editing or vector drawing program can be used to designor modify designs for laser cutting and engraving. Thus, modifying the structure ofa Fab@Home system does not require an investment in 3D CAD software to makeor publish new hardware designs, and the bitmap engraving possible with these lasercutters allows them to customize the appearance of their machine with images andtext.

5.5 Positioning

The linear motion components of the positioning system use off-the-shelf linear ball-bearing pillow blocks running on 1

2-inch diameter rails (McMaster-Carr, Inc.). The

X and Y axes are in a gantry configuration with the deposition tool riding on the Yaxis, which in turn rides on the X. The Z axis moves the build surface independentlyfrom the X and Y to minimize acceleration of parts as they are being fabricated. Wehave selected HSI Inc. linear stepper motors for our actuators because of their simpledesign, high resolution, and the semi-custom manufacturing focus of the company


Figure 5.3: (a) The standard design, single syringe tool, driven by a linear steppermotor; (b) A two-syringe version for a life-sciences laboratory.

which permits specifying precisely the leadscrew and bearing journal dimensions re-quired for our application, simplifying the overall design and assembly. For the X,Y,and Z axes we use NEMA size 14 bipolar motors with rotor-mounted lead screws.External polymer lead nuts are mounted to the axes carriages. In the case of the Xaxis, a timing belt and pulleys (Stock Drive Products, Inc.) are used to couple a slaveleadscrew to the motor leadscrew to achieve symmetrical drive of the gantry. Theforce, maximum speed, and positioning resolution all depend upon the lead screwthreading selected – in this case 15.8 µm travel per full step, a nominal top speed of25 mm/s (1600 step/s), and a maximum thrust of 120 N.

5.6 Material Deposition Tool

We have selected a syringe deposition tool for inclusion in the standard Model 1 designbecause of the broad range of materials useable with such tools, and for the intuitive-ness of operation. The syringe tool structure (Figure 5.3(a)) is also constructed oflaser cut acrylic parts with snap fit joinery and T-nut fasteners. A linear stepper

5.7. ELECTRONICS 43

motor controls the position of the syringe piston. We employ a NEMA size 8 framemotor with a rotor mounted lead nut. The lead screw, which is not captive in themotor, has 3.2 µm travel per full step, and the motor can achieve a top speed of 5.8mm/s (1800 step/s), and a maximum thrust of 90 N. For the 10cc syringes we use, thisamounts to a 1.1 cc/s maximum volume flow rate, and a maximum syringe pressureof 460 kPa (67 PSI). The current syringe tool has been designed to allow 10cc dispos-able syringe barrels (EFD, Inc.) to snap in and out, and for the piston to be quicklyattached and released from the motor leadscrew for quick changing of materials. Ametal nut fits tightly inside of disposable syringe pistons (EFD, Inc.), and one end ofthe motor leadscrew has threading to match the nut. When firmly threaded into thenut, the leadscrew is prevented from rotating with the motor rotor, and hence therotor motion is converted to linear motion. Manually unscrewing the leadscrew fromthe nut allows exchanging syringes, regardless of how full, without the need to moveor remove the piston. This facilitates the fabrication of multiple-material objects,and conserves materials.

We have also developed a dual syringe tool (Figure 5.3(b)) which allows twomaterials to be loaded simultaneously and independently deposited. As mentionedbefore, tools are bolted to the positioning system, and are modular.

5.7 Electronics

Personal computers today typically provide several USB connections, but no longerhave RS-232 serial ports or parallel ports, though these are still heavily used byrobotics and microcontroller hobbyists. As a result, we have opted to support directUSB connection to our Fab@Home Model 1 system, despite the additional develop-ment work and (internal) complexity that this entails. We chose to use a microcon-troller with an on-chip USB 2.0 peripheral, the Philips LPC-2148 ARM7TDMI (RoyalPhilips Electronics N.V.). This is a very high performance, 60MHz, flash-memorymicrocontroller with a wealth of peripheral functions for future expansion, includingADC, DAC, PWM, counter/timers, real-time clock, high-speed GPIO, UARTs, SPI,I2C, not to mention the USB2.0 peripheral. In addition, it has 512kB of flash mem-ory, and 40kB of RAM. The large program memory has enabled us to make a veryeasily understood and extensible packet data protocol for communication betweenthe PC application and the firmware. We use the large RAM space to buffer motioncommands so that real-time motion does not depend on variations in communicationbandwidth. With our current protocol, we can buffer roughly 670 6-dimensional pathpoints (for up to 6 axes of control). The microcontroller is powered by the USB,and thus can be communicated with even when the amplifier electronics are not pow-ered. The high computational performance of the device enables the system to handlereceiving and buffering path points, sending real-time status and position data, andcontrolling step and direction outputs for 6 axes at at least 5kHz. The microcontrolleris available on a 1.5-inch × 2.5-inch board (Figure 5.4(c)) with header connectors forall pins and a USB connector for $US39.95 in single quantity (LPC-H2148, Olimex,Inc.).


Figure 5.4: The electronics boards of the Model 1: (a) DB25 to screw terminalbreakout board at top center; (b) 4-axis stepper motor amplifier on the far right; (c)LPC-H2148 microcontroller board at bottom left

Currently, we are using a Xylotex 4-axis stepper motor amplifier board (Figure5.4(b)) to power the positioning system and syringe tool stepper motors. This boardprovides switch-mode current regulation for 4 bipolar stepper motors per board. Thecurrent regulation allows us to use a 30W laptop-style 24VDC power supply and 5Vrated motors to get much higher acceleration (hence faster builds at finer resolutions),than would be possible at the nominal 5V. This is a design decision which increasescost significantly (relative to using unipolar stepper motors) for the sake of makingthe technology more useable.

5.8 Software

The firmware for the LPC-2148 microcontroller was developed in C language, usingRowley CrossWorks for ARM integrated development environment (IDE) (RowleyCo. UK) which employs the free GNU GCC C/C++ compiler. CrossWorks is notessential - several freeware IDE’s, such as GNUARM exist which work with GNUGCC compiler. The firmware performs the following main functions:

• receiving and parsing of packetized commands from the PC via the USB

• buffering of motion path segments for fabrication paths

• immediate execution of jog motion and emergency stop commands

• configuration of limit switches (present/absent for each axis and direction)

5.8. SOFTWARE 45

Figure 5.5: A screenshot from the PC application displaying a model ready for fab-rication and dialog boxes for positioning and real-time status information

• communicating axes positions, limit switch states, and other system status tothe PC via the USB

• controlling step and direction outputs for up to 6 axes at > 5kHz step frequency

As mentioned before, the microcontroller has additional resources available forfuture expansion, and the firmware has been designed with ease of expansion in mind.

A PC application has been written which enables the user to control the machine,import, position, assign material properties to, and generate and execute manufactur-ing plans for geometry data which is imported in the form of STL files. In addition,the application has been designed around the concept that while the core applicationmay eventually be improved by the user community, in the short term, the hardwareconfiguration, the types of materials, and parameters for depositing materials wouldbe far simpler and more interesting to explore and share. Thus the hardware con-figuration, material properties, and material deposition parameters are described inplain text parameter files. These files describe, for instance, the color and geometrydata used to render the Fab@Home machine, the speeds and threading of the steppermotors, presence of limit switches, etc.

The PC application is currently targeted only for the Microsoft Windows (Mi-crosoft, Inc.) operating system. It is written in C++ using the Microsoft VisualStudio .NET (Microsoft, Inc.) development environment, OpenGL (SGI Inc.) for


graphics rendering, and the Microsoft Foundation Class library for user interfacecomponents. The application has been designed with the aim of maximizing theintuitiveness of use. The user interface (Figure 5.5) includes a 3D rendering of aFab@Home machine which moves synchronously with the real-time position informa-tion sent back by the microcontroller. Dialog boxes allow importing and assigningmaterial and tool properties to the part geometry, manual jogging of the axes via but-tons and mouse scroll wheel, including the syringe tool motor, as well as a numericalview of the real-time position and status data from the microcontroller. The appli-cation also allows a rudimentary simulation of the fabrication process – the actualmanufacturing plan is executed on a Fab@Home software emulator, and the motionsare displayed in the GUI for quick checking of toolpaths.

The workflow for Fab@Home consists of the following:

• connecting PC to Model 1 via USB cable, and plugging in the Model 1’s powersupply

• selecting and/or modifying/tuning parameter files to match the hardware andmaterials to be used

• starting the PC application

• loading the parameter files

• loading a syringe with piston, material, and nozzle, and mounting it in the tool;threading the tool leadscrew into the piston nut

• importing the geometry of the part to be fabricated

• assigning material and tool properties to part geometry

• automatic generation of a manufacturing plan

• if desired, simulated execution of the plan

• establishing communications with the Model 1

• homing of the axes so that GUI and physical positions match

• jogging axes to the desired origin for fabrication

• automatic execution of the manufacturing plan

5.9 Building a Model 1

To build and use a Model 1, you will need to do the following:

1. Buy tools required for assembly

2. Choose your style options

5.9. BUILDING A MODEL 1 47

3. Buy the parts for the Model 1

4. Build the cables

5. Build the Machine Base

6. Build the XY-Carriage

7. Build the Z-Carriage

8. Build the 1-Syringe Tool

9. Assemble the Chassis

10. Mounting the 1-Syringe Tool

11. Electronics Assembly

12. Program the LPC-H2148 with the Model 1 Firmware

13. Install the Fab@Home Model 1 Application

14. Commission the Model 1

15. Use the Model 1


Chapter 6

Background Material

6.1 Stepper motor

From Wikipedia, the free encyclopedia

A stepper motor is a brushless, synchronous electric motor that can divide afull rotation into a large number of steps, for example, 200 steps. Thus the motorcan be turned to a precise angle.

1. The top electromagnet (1) ischarged, attracting the topmostfour teeth of a sprocket.

2. The top electromagnet (1) isturned off, and the right electro-magnet (2) is charged, pulling thenearest four teeth to the right. Thisresults in a rotation of 3.6.

49

50 CHAPTER 6. BACKGROUND MATERIAL

3. The bottom electromagnet (3)is charged; another 3.6 rotationoccurs.

4. The left electromagnet (4) is en-abled, rotating again by 3.6. Whenthe top electromagnet (1) is againcharged, the teeth in the sprocketwill have rotated by one tooth po-sition; since there are 25 teeth, itwill take 100 steps to make a fullrotation.

6.1.1 Fundamentals of Operation

Stepper motors operate differently from normal DC motors, which simply spin whenvoltage is applied to their terminals. Stepper motors, on the other hand, effectivelyhave multiple ”toothed” electromagnets arranged around a central metal gear, asshown in the figures. To make the motor shaft turn, first one electromagnet is givenpower, which makes the gear’s teeth magnetically attracted to the electromagnet’steeth. When the gear’s teeth are thus aligned to the first electromagnet, they areslightly offset from the next electromagnet. So when the next electromagnet is turnedon and the first is turned off, the gear rotates slightly to align with the next one, andfrom there the process is repeated. Each of those slight rotations is called a ”step.” Inthat way, the motor can be turned a precise angle. There are two basic arrangementsfor the electromagnetic coils: bipolar and unipolar.

Unipolar motor

In a unipolar stepper motor, there are four separate electromagnets. To turn themotor, first coil ”1” is given current, then it’s turned off and coil 2 is given current,then coil 3, then 4, and then 1 again in a repeating pattern. Current is only sentthrough the coils in one direction; thus the name unipolar.

A unipolar stepper motor will have 5 or 6 wires coming out of it. Four of thosewires are each connected to one end of one coil. The extra wire (or 2) is called

6.1. STEPPER MOTOR 51

Figure 6.1: Because of induction of the windings, power requirements, and temper-ature management some glue circuitry is necessary between digital controller andmotor.


Figure 6.2: Different details of configuration have to be decided when choosing amotor. Almost everything is combineable.

6.1. STEPPER MOTOR 53

”common.” To operate the motor, the ”common” wire(s) is(are) connected to thesupply voltage, and the other four wires are connected to ground through transistors,so the transistors control whether current flows or not. A microcontroller or steppermotor controller is used to activate the transistors in the right order. This easeof operation makes unipolar motors popular with hobbyists; they are probably thecheapest way to get precise angular movements.

(For the experimenter, one way to distinguish common wire from a coil-end wireis by measuring the resistance. Resistance between common wire and coil-end wire isalways half of what it is between coil-end and coil-end wires. This is due to the factthat there is actually twice the length of coil between the ends and only half fromcenter (common wire) to the end.)

Bipolar motor

There are only two coils, and current must be sent through a coil first in one directionand then in the other direction; thus the name bipolar. Bipolar motors need morethan 4 transistors to operate them, but they are also more powerful than a unipolarmotor of the same weight. To be able to send current in both directions, engineerscan use an H-bridge to control each coil or a step motor driver chip.

Theory

A step motor can be viewed as a DC motor with the number of poles (on bothrotor and stator) increased, taking care that they have no common denominator.Additionally, soft magnetic material with many teeth on the rotor and stator cheaplymultiplies the number of poles (reluctance motor). Like an AC synchronous motor,it is ideally driven by sinusoidal current, allowing a stepless operation, but this putssome burden on the controller. When using an 8-bit digital controller, 256 microstepsper step are possible. As a digital-to-analog converter produces unwanted ohmic heatin the controller, pulse-width modulation is used instead to regulate the mean current.Simpler models switch voltage only for doing a step, thus needing an extra currentlimiter: for every step, they switch a single cable to the motor. Bipolar controllerscan switch between supply voltage, ground, and unconnected. Unipolar controllerscan only connect or disconnect a cable, because the voltage is already hard wired.Unipolar controllers need center-tapped windings.

It is possible to drive unipolar stepper motors with bipolar drivers. The idea isto connect the output pins of the driver to 4 transistors. The transistor must begrounded at the emitter and the driver pin must be connected to the base. Collectoris connected to the coil wire of the motor.

Stepper motors are rated by the torque they produce. Synchronous electric motorsusing soft magnetic materials (having a core) have the ability to provide positionholding torque (called detent torque, and sometimes included in the specifications)while not driven electrically. To achieve full rated torque, the coils in a stepper motormust reach their full rated current during each step. The voltage rating (if there isone) is almost meaningless. The motors also suffer from EMF, which means that once


Figure 6.3: A typical leadscrew and nut assembly.

the coil is turned off it starts to generate current because the motor is still rotating.There needs to be an explicit way to handle this extra current in a circuit otherwiseit can cause damage and affect performance of the motor.

6.1.2 Applications

Computer-controlled stepper motors are one of the most versatile forms of positioningsystems, particularly when digitally controlled as part of a servo system. Steppermotors are used in floppy disk drives, flatbed scanners, printers, plotters and manymore devices. Note that hard drives no longer use stepper motors to position theread/write heads, instead utilising a voice coil and servo feedback for head positioning.

Stepper motors can also be used for positioning of valve pilot stages, for fluidcontrol systems.

6.2 Haydon Switch and Instrument Co.: Leadscrews

Lead Screws

The design of many devices require linear motion, there are several ways throughwhich this can be achieved. One of the most effective ways to generate linear motionis through the use of a rotating screw and a nut that translates along the length of thescrew. There are several thread forms that have been developed over the years that aretailored to specific needs. The 60 V thread is commonly used on fasteners due to itsholding strength and ease of manufacture. The 29 Acme thread was developed over100 years ago to efficiently transmit thrust loads along the length of the screw, thusconverting rotary motion into linear motion. Haydon has over 25 years of experiencein converting rotary motion to linear motion in our line of linear actuators. As linearsystems have evolved there are several features that have become critical to ensureproper function of the system. Some of these features include: accuracy, repeatability,life, maximum load and efficiency.

6.2. HAYDON SWITCH AND INSTRUMENT CO.: LEADSCREWS 55

Figure 6.4: Anti-backlash nuts and nut assemblies.

When a leadscrew and nut are used to generate linear motion there are someclearances between the two parts to allow them to fit together with no interference.These clearances are essential to the system but can lead to backlash or “lost motion”when reversing the direction of the load.

Anti-Backlash Nuts & Nut Assemblies

Haydon offers 4 different styles of nuts from a free wheeling non antibacklash nutto a user adjustable anti-backlash nut. All of these nut styles are available on screwsranging from 1/8” [3.2mm] to 5/8” [15.9mm] in diameter with leads as fine as 0.012”[0.3mm] up to fast leads as high as 1.25” [31.75mm]. Contact Haydon today for yourcustom linear motion solution.

Haydon’s new series of nuts and nut assemblies for our hybrid external linearactuators are manufactured with a proprietary blend of self-lubricating polyacetal.This nut material in conjunction with our precision rolled 303 stainless steel screwmaterial provides low drag torque and smooth operation throughout the life of theassembly.

Hybrid Linear Actuators

Haydon’s line of hybrid linear actuators opens new avenues for equipment design-ers who require high performance and exceptional endurance in a very small package.The various patent pending designs use a proprietary manufacturing process, whichincorporates engineering thermoplastics in the rotor drive nut and a stainless steelacme leadscrew. This allows the motor to be much quieter, more efficient and moredurable than the v-thread and bronze nut configuration commonly used in other actu-ators. Motor life is improved more than 10 times over the traditional bronze nut style– and it requires no maintenance and does not affect the cost. An additional featureis the bearing pre-load adjustment which, unlike other designs, does not protrudefrom the motor configuration commonly used in other actuators.

The Haydon hybrid actuators come in six sizes, from 21 mm square to 87 mmsquare. Each size has three designs available – captive, non-captive and an externallinear version. There are over twenty different travels per step available, from .00006inch (.001524 mm) to .005 inch (.127 mm). Micro stepping can be used for even finer


Figure 6.5: Hybrid Linear Actuators.

resolution.These linear actuators are ideal for applications requiring a combination of precise

positioning, rapid motion and long life. Typical applications include X-Y tables,medical equipment, semiconductor handling, telecommunications equipment, valvecontrol, and numerous other uses.Canstack Linear Actuators

The Haydon line of can stack linear actuators provides both a broader rangeand, for a given size, significantly higher thrust than previously available from mini-steppers. Five basic frame sizes are available, 15 mm (.59”), 20 mm (.79”), 26mm (1”), 36 mm (1.4”) and 46 mm (1.8”). Available step increments vary withthe motor frame sizes and are dependent on the basic step angle of the motor andthe leadscrew pitch. A captive, external or non-captive shaft (leadscrew) option canbe supplied for almost every size. The captive shaft configuration features a built-in“anti-rotation” design. The non-captive shaft option requires the customer to provideexternal anti-rotation. The external linear actuators incorporate a rotary leadscrewand an external translating nut. These motors are ideal for applications where thereis no space behind the motor for a through-screw design. Both unipolar and bipolarcoil configurations are available.

Haydon’s patented design accepts a larger rotor than conventional units, improv-ing efficiency and eliminating the need for massive heat sinks. Unique Haydon featuresimpart ruggedness and reliability that assure long life and consistent performance.Rare earth magnets are available for even higher thrust. All units are built with dualball bearings for greater motion control, precise step accuracy and long life.

Applications include medical instrumentation, machinery automation, entertain-ment, semiconductor, robotics, sophisticated pumping systems and other automateddevices which require precise remote controlled linear movement in a broad range oftemperature environments

Haydon Switch and Instrument CompanyA Tritex Corporation Company1500 Meriden Road Waterbury, CT 06705

6.3. HSI 35000 SERIES: SIZE 14 LINEAR ACTUATORS 57

Figure 6.6: Hybrid Linear Actuators.

Tel: 203-756-7441 Fax: 203-756-8724 Toll Free: 800-243-2715Site Support by: Progressive Software Solutions

6.3 HSI 35000 Series: Size 14 Linear Actuators

See URL http://www.hsi-inc.com/index.phpHSI’s Size 14 hybrid linear actuators have been improved to provide higher force,

longer life and improved performance. The various patent pending designs deliverexceptional performance and new linear motion design opportunities. Three designsare available, captive, non-captive and external linear versions. The 35000 Series isavailable in a wide variety of resolutions - from 0.00012" (.003048 mm) per step to0.00192" (.048768 mm) per step. The motors can also be microstepped for even finerresolutions. The Size 14 actuator delivers thrust of up to 50 lbs. (23 Kg).

Captive Non-Captive External


Salient Characteristics - Series 35000 Size 14 Linear Actuator(Size 14: 35mm (1.4") Hybrid Linear Actuator 1.8 degree step angle)

Captive 35H4(X)-V 35H6(X)-V

Part No. Non-Captive 35F4(X)-V 35F6(X)-V

External Lin. E35H4(X)-V E35H6(X)-V

Wiring Bipolar Unipolar**

Operating voltage 2.33 VDC 5 VDC 12 VDC 5 VDC 12 VDC

Current/phase 1.25 A 0.57 A 0.24 A 0.57 A 0.24 A

Resistance/phase 1.86 Ω 8.8 Ω 50.5 Ω 8.8Ω 50.5 Ω

Inductance/phase 2.8 mH 13 mH 60 mH 6.5 mH 30 mH

Power consumption 5.7 W

Rotor inertia 27 gcm2

Temperature rise 135F (75C)

Weight 5.7 oz (162 g)

Insulation resistance 20 MΩ

**Unipolar drive gives approximately 30% less thrust than bipolar drive.

Linear Travel / StepScrew 0.218" (5.54 mm)

OrderCode

mm inches I.D.0.00048 0.0121 J0.00024 0.0060 K0.00012 0.0030 N0.00096 0.0243 Q0.00192 0.0487 R


OrderCode

mm inches I.D.0.00031250 0.007900 A0.00062500 0.015800 B0.00125000 0.031700 C0.00015625 0.00390000 P

Standard motors are Class B rated for maximum temperature of 130oC.Special drive considerations may be necessary when leaving shaft fully extended

or fully retracted.


Salient Characteristics - Series 35000 Size 14 Hybrid Linear Actuator(Size 14: 35mm (1.4") Hybrid Linear Actuator 0.9 degree step angle)

Captive 35K4(X)-V 35K6(X)-V

Part No. Non-Captive 35J4(X)-V 35J6(X)-V

External Lin. E35K4(X)-V E35K6(X)-V





Inductance/phase 0 mH 0 mH 60 mH 0 mH 0 mH








OrderCode

mm inches I.D.0.00048 0.0121 J0.00024 0.0060 K0.00012 0.0030 N0.00096 0.0243 Q0.00006 0.0015 U


OrderCode

mm inches I.D.0.00031250 0.0079 A0.00062500 0.0158 B0.00015625 0.0039 P0.00007800 0.0020 V

Standard motors are Class B rated for maximum temperature of 130oC.Special drive considerations may be necessary when leaving shaft fully extended

or fully retracted.


DIMENSIONAL DRAWING - 35000 SERIES SIZE 14 LINEAR ACTUATORCAPTIVE SHAFT

DIMENSIONAL DRAWING - 35000 SERIES SIZE 14 LINEAR ACTUATORNON-CAPTIVE LINEAR


DIMENSIONAL DRAWING - 35000 SERIES SIZE 14 LINEAR ACTUATOREXTERNAL LINEAR



Ramping can increase the performance of a motor either by increasing the topspeed or getting a heavier load accelerated up to speed faster. Also, deceleration canbe used to stop the motor without overshoot.

NOTE: All chopper drive curves were created with a 5 volt motor and a 40 voltpower supply.

6.4 HSI 28000 Series: Size 11 Linear Actuators

See URL http://www.hsi-inc.com/index.php


HSI’s Size 11 hybrid linear actuators are one of our more compact additions toan extensive line of production proven miniature motors. The various patent pend-ing designs deliver high performance, opening avenues for equipment designers whorequire performance and endurance in a very small package. Three designs are avail-able, captive, non-captive and external linear versions. The 28000 Series is availablein a wide variety of resolutions - from 0.000125" (.003175 mm) per step to 0.002"(.0508 mm) per step. The Size 11 actuator delivers thrust of up to 25 lbs. (11.5 Kg).

Captive Non-Captive External


Salient Characteristics - Series 28000 Size 11 Linear Actuator(1.8 degree step angle)

Captive 28H4(X)-V 28H6(X)-V

Part No. Non-Captive 28F4(X)-V 28F6(X)-V

External Lin. E28H4(X)-V E28H6(X)-V





Inductance/phase 1.5 mH 6.7 mH 39. mH 3.3 mH 19.5 mH








OrderCode

mm inches I.D.0.001000 0.0254 10.002000 0.0508 20.000500 0.0127 30.000125 0.0031 70.000250 0.0063 9


DIMENSIONAL DRAWING - 28000 SERIES SIZE 11 LINEAR ACTUATORCAPTIVE SHAFT

DIMENSIONAL DRAWING - 28000 SERIES SIZE 11 LINEAR ACTUATORNON-CAPTIVE LINEAR


DIMENSIONAL DRAWING - 28000 SERIES SIZE 11 LINEAR ACTUATOREXTERNAL LINEAR


Ramping can increase the performance of a motor either by increasing the top speedor getting a heavier load accelerated up to speed faster. Also, deceleration can beused to stop the motor without overshoot.

NOTE: All chopper drive curves were created with a 5 volt motor and a 40 voltpower supply.

6.5 Deposition Tools

A deposition tool is a device which is mounted on a Fab@Home chassis, and whichcan deposit material in a controlled fashion to allow the Fab@Home system to build upa three-dimensional object, layer by layer. Here you can look at all of the depositiontools developed for the Fab@Home family of fabbers.

6.5.1 Syringe Tools

A syringe tool is a deposition tool which controls the dispensing of material from asyringe. Syringe tools can be used with almost any fluid or paste material. With theaddition of temperature control, materials that are solid at room temperature canalso be used. Additionally, the materials do not typically need to be very carefullyfiltered to achieve reasonable results. The drawbacks of syringe tools are:

• Resolution limited by needle/nozzle diameter - difficult to get below 100 mi-crometers

• Need to precisely control the height of the needle/nozzle relative to the objectbeing built

6.5. DEPOSITION TOOLS 69

– If too large a gap, the material will tend to bead up and drip from thesyringe

– If too small a gap, the needle/nozzle will plough through previously de-posited layers

Many methods exist for controlling the flow of material from a syringe, including:

• A linear motor driving the syringe piston

• Controlled flow of compressed gas (e.g. air) into the syringe

• Constant pressure compressed gas behind the material in the syringe with acontrolled valve at the syringe tip

Model 1 1-Syringe Tool

The standard Model 1 1-Syringe Tool

The Model 1 1-Syringe Tool is the standard deposition tool for the Fab@HomeModel 1. It uses the linear stepper motor method of controlling syringe piston po-sition, hence material flow. This is the recommended tool for beginner fabbers, inthat it allows the use of a very wide variety of materials, the materials do not needcareful preparation, it operates in an intuitive fashion, and allows simple swapping ofmaterial syringes to build objects with multiple materials.




The Model 1 2-Syringe Tool is a simple modification to the 1-Syringe tool, justwider, with 2 motors, and two syringes. At present only the SolidWorks design filesare available. The assembly is essentially identical to that of the 1-Syringe tool.PLEASE NOTE: The 2-Syringe Tool has an additional motor which willrequire an additional motor amplifier, and the addition of a couple of cableconnections between the microcontroller and the additional amplifier.

6.5.2 Ink-jet Tools

Ink-jet technology is very well developed for the document printing market. Commer-cial ink-jets require very carefully filtered materials to prevent clogging of the veryfine jet orifices. The materials must have very well controlled (and low) viscosity toform tiny droplets which can be ejected cleanly from the orifice.

Standard Ink-jet technology (printer heads) are currently being used for 3d fabri-cation for example Z-Corp (http://www.zcorp.com/products/printersdetail.asp?ID=1) uses standard HP Ink-jet cartridges to spray an image a sliceat a time onto a layer of powder once a slice has been printed a thin layer of powderis deposited the printer then prints another 2d slice the process is repeated until a3D physical object has been created. The loose powder is vacuumed out leaving thephysical object to be removed.

The problem I see with homebrew systems using this technology is that the printerhead firmware is tied up (i.e. closed to HP and affiliates) meaning it is very difficult/ impossible to code for it. To go down this route one would probably need to createthere own print head controller as in: http://www.spritesmods.com/?art=inker

I decided to take another approach and to use the existing HP firmware. I dis-mantled an old HP Inkjet and cobbled together a crude X axis controlled by a PIC

6.5. DEPOSITION TOOLS 71

4455 the trick is to move the X axis position the same distance as a piece of paperwould move and to monitor position of the X axis so as home the X axis back to itsoriginal location so as to be able to print the next layer over the top of the first andso on. Note before the X axis home(s)it is necessary to lower the base by the amountof the slice height the X axis then drags / scrapes a new thin layer of powder acrossthe last slice printed then the printer continues printing the next slice.

With regards to deposition material (binder) for the inkjet cartridge I mixedtogether sugar water using distilled water the idea being sugar dissolves and solidifiesacting as a glue to bind the powder. I could successfully print though the ink jetcartridges were quite old i.e. it had been refilled with ink at least twice in the past.

One benefit of using this method is that the unused powder also acts as a supportmaterial for overhangs etc.

–Paragon 15:26, 15 November 2006 (EST)

6.5.3 Fountain Pen Tools

A fountain pen tool is a deposition tool which operates exactly like a fountain pen. Acompliant (flexible) nib or tip is dragged over the surface on which the material is tobe deposited. The nib has a fine channel down which fluid flows by capillary action.The fluid needs to be carefully filtered, and of low viscosity (about like water). Thefountain pen tool can achieve very high resolution (limited by the size of the nib tip,and the surface energy of the fluid (the wettability) on the substrate or previous layer.A fountain pen tool is well-suited to drawing electronic circuits using conductive inks,organic polymer semiconductors, etc.

Fuel Injectors

On finding this fantastic website I emailed Evan with some thoughts and ideas thatI have been working on. One of these ideas was with regards to using an electronicautomotive fuel injector as a depositition tool. I had four injectors purchased viaeBay which where like new removed from a mini. Over the weekend I carried outsome basic tests. I hooked the terminals up to a MOSFET with the gate connectedto the output of a PIC this allowed me to switch the injector on and off at variousrates. I did not have a pump available so I used a large syringe that came with aninkjet refill kit connected to the input of the injector. Initially I filled the syringe withwater to check the flow this flowed with no problem. I then filled the syringe with ahand cream called E45 (It was all I had available)in the UK this is fairly viscous soI was concerned that the injector would become blocked. I am pleased to say it didnot.

I then connected a very fine hypodermic needle (which was left over from buildinga gas turbine fuel injector and not drug abuse! ;-)) to the output of the injectoron switching the injector on and off a consistent very fine interrupted stream waswitnessed.

–Paragon 15:24, 15 November 2006 (EST)

Worm Driven Extruder

A picture speaks a thousand words:


–Paragon 05:18, 16 November 2006 (EST)Laser

I seem to recall an early rapid prototyping machine using a laser to solidify liquidplastic, then the model was lowered down into the plastic, one layer at a time. Hasthis been experimented with with the Fab@Home, or is it an outmoded method thatwould require too much time/effort to be truly practicable?

I will do some research, as it seems that the deposition tool/material is the realsticking point for the whole program. (At least to my eyes)

Stepper motor technology is mature, and well understood, as CNC machining isactually coming to the home market. Check out 5Bears, a guy who actually madehis own CNC mill. But deposition, aye, there’s the rub.

Great stuff here. Von Neumann, [email protected] prototyping can enhance the capabilities in the rapid prototyping (RP)

arena, by allowing a greater range of materials to be used. It can even facilitate theRP of metalic objects. The approach is to heat a layer of metallic powder to nearmelting point and to trace a laser over areas to be fused. The extra energy that thelaser adds is just enough to melt the material and fuses it to the object. Once thelayer has been fused a new layer of powder is laid down and the process is repeated.

Laser engraver for sintering?Ran across this and thought perhaps it might be adaptable for laser sintering non-

metals... It’s a small computer driven laser engraver... If it can engrave something, it

6.6. MICROCONTROLLER 73

oughta be able to sinter it, right? If you could drive the mechanism directly, all you’dneed to add would be vertical travel on the tray, and a roller/grader to push a newlayer of powder over the workpiece... Or maybe just mount the laser on the fab caseand a couple of mirrors on the axis travel mechanism to point the laser down wherethe syringe would be... Just random thoughts, this isn’t really my area of expertise.Yet. Anyway, here’s the link...

http://www.iehk.net/Products/IE300.html

Kent

It seems that the cheapest that you can get a second-hand CO2 laser in the 30-40Wrange is about $1000. Despite my initial feeling that ”it’s just a couple of of mirrors,some low pressure CO2 and a bulb” it seems that they are not easy to build (butI’m keeping an open mind, I feel that when your needs are specific there is usually afudge/hack/shortcut that will get you there). Also delivering the beam from a CO2laser is not easy. Unlike solid-state lasers, I don’t think the price scales rapidly withpower. I have been wondering how narrow we could focus a beam and how muchpower we would need. Clearly the rate of incoming energy / outgoing energy is acomplicated thing, certainly not just a matter of x Watts per square meter. Thisall depends on grain size, material, focus, temperature etc. The only real solution isexperimentation. But we need a plausible design to work with first. Otherwise usinga focussed and screened bulb or array thereof may be more suited to home-building.Again such an array is not easily mounted and it would be necessary to come up witha clever system for beam delivery.

Casper

Here’s what seems to be a very detailed FAQ on CO2 laser DYI –http://www.repairfaq.org/sam/lasercc2.htm – and from the looks of it, building alaser is more expensive than buying a used one (“save your money and look fora used laser” draws my attention). But isn’t the chassis of the Model 1 laser-cutplastic? Wouldn’t it be nice if the laser were a tool included in the basic design? Istill like the idea of the self-assembling machine shop.

Michael

6.6 Microcontroller


It has been suggested that this article or section be merged with embedded micro-processor. (Discuss)


The integrated circuit from an Intel 8742, an 8-bit microcontroller that includes aCPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the

same chip.

A microcontroller (or MCU) is a computer-on-a-chip. It is a type of micro-processor emphasizing self-sufficiency and cost-effectiveness, in contrast to a general-purpose microprocessor (the kind used in a PC).

6.6.1 Embedded design

The majority of computer systems in use today are embedded in other machinery, suchas telephones, clocks, appliances, vehicles, and infrastructure. An embedded systemusually has minimal requirements for memory and program length and may requiresimple but unusual input/output systems. For example, most embedded systems lackkeyboards, screens, disks, printers, or other recognizable I/O devices of a personalcomputer. They may control electric motors, relays or voltages, and read switches,variable resistors or other electronic devices. Often, the only I/O device readable bya human is a single light-emitting diode, and severe cost or power constraints caneven eliminate that.

6.6.2 Higher Integration

In contrast to general-purpose CPUs, microcontrollers do not have an address busor a data bus, because they integrate all the RAM and non-volatile memory on thesame chip as the CPU. Because they need fewer pins, the chip can be placed in amuch smaller, cheaper package.

Integrating the memory and other peripherals on a single chip and testing themas a unit increases the cost of that chip, but often results in decreased net cost ofthe embedded system as a whole. (Even if the cost of a CPU that has integratedperipherals is slightly more than the cost of a CPU + external peripherals, havingfewer chips typically allows a smaller and cheaper circuit board, and reduces the laborrequired to assemble and test the circuit board).

A microcontroller is a single integrated circuit, commonly with the following fea-tures:


• central processing unit - ranging from small and simple 4-bit processors tosophisticated 32- or 64-bit processors

• input/output interfaces such as serial ports (UARTs)

• other serial communications interfaces like I2C, Serial Peripheral Interface andController Area Network for system interconnect

• peripherals such as timers and watchdog

• RAM for data storage

• ROM, EPROM, EEPROM or Flash memory for program storage

• clock generator - often an oscillator for a quartz timing crystal, resonator or RCcircuit

• many include analog-to-digital converters

This integration drastically reduces the number of chips and the amount of wiringand PCB space that would be needed to produce equivalent systems using separatechips and have proved to be highly popular in embedded systems since their intro-duction in the 1970s.

Some microcontrollers can afford to use a Harvard architecture: separate memorybuses for instructions and data, allowing accesses to take place concurrently.

The decision of which peripheral to integrate is often difficult. The Microcontrollervendors often trade operating frequencies and system design flexibility against time-to-market requirements from their customers and overall lower system cost. Man-ufacturers have to balance the need to minimize the chip size against additionalfunctionality.

Microcontroller architectures are available from many different vendors in so manyvarieties that each instruction set architecture could rightly belong to a category oftheir own. Chief among these are the 8051, Z80 and ARM derivatives.[citationneeded]

6.6.3 Large Volumes

Microcontrollers take the largest share of sales in the wider microprocessor market.Over 50% are ”simple” controllers, and another 20% are more specialized digitalsignal processors (DSPs)[citationneeded]. A typical home in a developed country is likelyto have only one or two general-purpose microprocessors but somewhere between oneand two dozen microcontrollers. A typical mid range automobile has as many as 50or more microcontrollers. They can also be found in almost any electrical device:washing machines, microwave ovens, telephones etc.


A PIC 18F8720 microcontroller in an 80-pin TQFP package.

Manufacturers have often produced special versions of their microcontrollers inorder to help the hardware and software development of the target system. Thesehave included EPROM versions that have a ”window” on the top of the device throughwhich program memory can be erased by ultra violet light, ready for reprogrammingafter a programming (”burn”) and test cycle. Other versions may be available wherethe ROM is accessed as an external device rather than as internal memory. A simpleEPROM programmer, rather than a more complex and expensive microcontrollerprogrammer, may then be used, however there is a potential loss of functionalitythrough pin outs being tied up with external memory addressing rather than forgeneral input/output. These kind of devices usually carry a cost up in part pricesbut if the target production quantities are small, certainly in the case of a hobbyist,they can be the most economical option compared with the set up charges involved inmask programmed devices. A more rarely encountered development microcontrolleris the ”piggy back” version. This device has no internal ROM memory; instead pinouts on the top of the microcontroller form a socket into which a standard EPROMprogram memory device may be installed. The benefit of this approach is the releaseof microcontroller pins for input and output use rather than program memory. Thesekinds of devices are normally expensive and are impractical for anything but thedevelopment phase of a project.

6.6.4 Programming Environments

Originally, microcontrollers were only programmed in assembly language, or later inC code. Recent microcontrollers integrated with on-chip debug circuitry accessedby In-circuit emulator via JTAG enables a programmer to debug the software of anembedded system with a debugger.

Some microcontrollers have begun to include a built-in high-level programminglanguage interpreter for greater ease of use. The Intel 8052 and Zilog Z8 were availablewith BASIC very early on, and BASIC is more recently used in the popular BASICStamp MCUs.


Some microcontrollers such as Analog Device’s Blackfin processors can be pro-grammed using LabVIEW, which is a high level programming language.

6.6.5 Interrupt Latency

In contrast to general-purpose computers, microcontollers used in embedded systemsoften seek to minimize interrupt latency over instruction throughput.

When an electronic device causes an interrupt, the intermediate results, the reg-isters, have to be saved before the software responsible for handling the interrupt canrun, and then must be put back after it is finished. If there are more registers, thissaving and restoring process takes more time, increasing the latency.

Low-latency CPUs generally have relatively few registers in their central pro-cessing units, or they have ”shadow registers” that are only used by the interruptsoftware.

6.6.6 Development platforms for hobbyists

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For almost every manufacturer of bare microcontrollers, there are a dozen littlecompanies repacking its products into more hobbyist-friendly packages. Their productis often an MCU preloaded with a BASIC or similar interpreter, soldered onto a DualInline Pin board along with a power regulator and other goodies. PICmicros seem tobe very popular here, possibly due to good static protection. More powerful examples(e.g. faster execution, more RAM and code space) seem to be based on Atmel AVRor Hitachi chips and now ARM.

Arduino

Arduino is an open-source physical computing platform based on a simple input/outputboard and a development environment that implements the Processing/Wiring lan-guage. Arduino can be used to develop stand-alone interactive objects or can beconnected to software on your computer (e.g. Flash, Processing, MaxMSP). Theboards can be assembled by hand or purchased preassembled; the open-source IDEcan be downloaded for free. Arduino uses an ATmega8 or ATmega168 microcontrollerfrom Atmel’s Atmel AVR series.

Platforms from Parallax, Inc.

BASIC Stamp by Parallax, is the ’big name’ in BASIC microcontrollers. They areMicrochip PIC micros programmed with an interpreter that processes the programstored in an external EEPROM. Several different modules are available of varyingprocessing speeds, RAM, and EEPROM sizes. Most popular is the original BASIC


Stamp 2 module. The BASIC Stamp is used by Parallax as a platform for introductoryprogramming and robotic kits.

SX-Key, Parallax’s development tool for the SX line of microcontrollers, support-ing every SX chip commercially available. Using free SX-Key software (Assemblylanguage), or the SX/B Compiler (BASIC-style language) from Parallax, the SX-Keyprogramming tool can program SX chips in-system and perform in-circuit source-leveldebugging.

Propeller, A multi-core microcontroller developed by Parallax, Inc. It featureseight 32bit cores and 32 I/O pins in the currently released version. Each core operatesindependently at 80Mhz, it is programmed in a language named SPIN(tm) which wasdeveloped by Parallax to support this unique micro.

PICAXE

This PICAXE range of controllers from Revolution Education Limited[1] are basedupon Microchip PICmicro’s programmed with a BASIC interpreter. Using internalEEPROM or Flash to store the user’s program they deliver a single-chip solution andare quite inexpensive. A PICAXE programmer is simply a serial plug plus two resis-tors. Complete development software, comprehensive documentation and applicationnotes are all available free of charge.

The BASIC-like programming language is almost identical to that used by Par-allax’s Basic Stamp 1 (BS1) but has been enhanced to support on-chip hardwareand additional functionality. In common with the BS1 programming language, thePICAXE has support only for a limited number of variables, but allows access tointernal RAM for storage which helps overcome that limitation.

The 5.0.X versions of the Visual IDE ( the Programming Editor ) introduced’enhanced compilers’ which support block-structured programming constructs plusconditional compilation and other directives.

Initially targeted at the UK educational sector, use of the PICAXE has spreadto hobbyists, semi-professionals and it can also be found inside commercial prod-ucts. With its user base in many countries, the PICAXE has steadily gained a goodinternational reputation.

A-WIT Technologies, Inc.

A-WIT Technologies, Inc.[2] has a microcontroller module named the C STAMP, alongwith support boards, kits, and software tools and infrastructure. The C STAMP isdesigned around a PIC microcontroller, and is programmed in a very user friendlysubset of the standard C language called WC that is easy and powerful, because itrelies on A-WIT’s supplied software infrastructure. This microcontroller module isvery affordable, and it has 48 pins, 35 KiB of memory, and runs at 40 MHz. TheC STAMP also has a vast array of accessories and components, which are supportedby A-WIT’s software interfaces that enables seamless connectivity. This, in turn,enhances the ease of complete system development.


Comfile Technology Inc.

Comfile Technology Inc.[3] produces a series of microcontrollers branded as CUBLOCand CuTOUCH, using the Atmel ATmega128 processor. They are very price compet-itive, being aimed at industrial applications, and include some nice features such asLadder Logic in addition to BASIC, a huge 80 KiB program memory, and hardwarepulse width modulation. Their focus is on developing industrial controllers which arefast, easy-to-use, and versatile. Comfile Technology’s CuTOUCH is a visual Touch-screen controller that can be programmed in BASIC and Ladder Logic. This productis the first of its kind in the world yet.

Coridium ARMexpress

ARMexpress[4] is the first of a new family of DIP-24 (stamp-sized) controllers thatcombine a 60 MHz ARM CPU with a builtin BASIC compiler to achieve new levelsof performance in this form factor. This combination makes this simple to use butvery fast controller a good choice for the prototype builder or system integrator. 40Kof code and 40K of data are available to the user, and code speed rivals that ofprograms written in C. The dialect of BASIC conforms more to Visual BASIC, buthas hardware extensions like PBASIC.

ZX-24, ZX-40, ZX-44

The ZX series[5] MCUs are based on the Atmel ATmega32 and ATmega644 pro-cessors. The devices run a field-upgradable Virtual Machine that features built-inmulti-tasking, 32-bit floating point math and 1.5K to 3.5K of RAM for user’s pro-grams. Multi-tasking facilitates a more structured approach to coding for interfacedevices that require prompt service, e.g. serial devices, infrared remotes, etc.

The programming language for the ZX series is ZBasic, a modern dialect of Basicmodeled after Microsoft’s Visual Basic. The biggest improvement over the typicalMCU Basic dialect is the availability of parameterized subroutines/functions thatsupport local variables. Strong type checking is another improvement that aids inwriting correct programs more quickly. User-defined types (structures) are also sup-ported along with aliases, based variables, sub-byte data types (Bit and Nibble) andother advanced capabilities.

6.6.7 See also

• Embedded systems

• Embedded computer

• Microarchitecture

• In-circuit emulator (ICE)

• List of common microcontrollers


• Microbotics

• Contiki – A small-footprint open source, yet fully featured, operating systemdeveloped for use on a number of smallish to large industrial systems rangingfrom 8-bit computers to embedded microcontrollers.

Wikibooks has more about this subject: Embedded Systems

6.7 Universal Serial Bus

From Wikipedia, the free encyclopediaUniversal Serial Bus

• The USB ”trident” Icon

• Year Created: January 1996

• Width: 1 bits

• Number of Devices: 127 per host

• Speed: Up to 480 Mbit/s (USB 2.0)

• Style: Serial

• Hotplugging? Yes

• External? Yes

Universal Serial Bus (USB) is a serial bus standard to interface devices. Amajor component in the legacy-free PC, USB was designed to allow peripherals tobe connected using a single standardised interface socket, to improve plug-and-playcapabilities by allowing devices to be connected and disconnected without reboot-ing the computer (hot swapping). Other convenient features include powering low-consumption devices without the need for an external power supply and allowingsome devices to be used without requiring individual device drivers to be installed.

USB is intended to help retire all legacy serial and parallel ports. USB can con-nect computer peripherals such as mouse devices, keyboards, PDAs, gamepads andjoysticks, scanners, digital cameras and printers. For many devices such as scannersand digital cameras, USB has become the standard connection method. USB is alsoused extensively to connect non-networked printers; USB simplifies connecting severalprinters to one computer. USB was originally designed for personal computers, butit has become commonplace on other devices such as PDAs and video game consoles.In 2004, there were about 1 billion USB devices in the world.[citationneeded]

6.7. UNIVERSAL SERIAL BUS 81

The design of USB is standardized by the USB Implementers Forum (USB-IF),an industry standards body incorporating leading companies from the computer andelectronics industries. Notable members have included Apple Computer, Hewlett-Packard, NEC, Microsoft, Intel, and Agere.

6.7.1 History

Original USB Logo

As of 2006, the USB specification is at version 2.0 (with revisions). Hewlett-Packard, Intel, Lucent, Microsoft, NEC, and Philips jointly led the initiative to de-velop a higher data transfer rate than the 1.1 specification. The USB 2.0 specificationwas released in April 2000 and was standardized by the USB-IF at the end of 2001.Previous notable releases of the specification were 0.9, 1.0, and 1.1. Equipment con-forming with any version of the standard will also work with devices designed to anyprevious specification (known as: backward compatibility).

Smaller USB plugs and receptacles for use in handheld and mobile devices, calledMini-B, were added to USB specification in the first engineering change notice. Anew variant of smaller USB plugs and receptables, Micro-USB, was announced by theUSB Implementers Forum on January 4, 2007 [1].

6.7.2 Overview

A USB system has an asymmetric design, consisting of a host controller and multipledaisy-chained peripheral devices. Additional USB hubs may be included in the chain,allowing branching into a tree structure, subject to a limit of 5 levels of branching percontroller. No more than 127 devices, including the bus devices, may be connectedto a single host controller. Modern computers often have several host controllers,allowing a very large number of USB devices to be connected. USB cables do notneed to be terminated.


A USB hub

In USB terminology, individual devices are referred to as functions, because eachindividual physical device may actually host several functions, such as a webcamwith a built-in microphone. Functions are linked in series through hubs. The hubsare special-purpose devices that are not considered functions. There always existsone hub known as the root hub, which is attached directly to the host controller.USB endpoints actually reside on the connected device: the channels to the host arereferred to as pipes

Functions and hubs have associated pipes (logical channels). Pipes are connectionsfrom the host controller to a logical entity on the device named an endpoint. The termendpoint is also occasionally used to refer to the entire pipe. A function can have up to32 active pipes, 16 into the host controller and 16 out of the controller. Each endpointcan transfer data in one direction only, either into or out of the device/function, soeach pipe is uni-directional.

A USB endpoints

When a device is first connected, the host enumerates and recognizes it, and loadsthe device driver it needs. When a function or hub is attached to the host controllerthrough any hub on the bus, it is given a unique 7 bit address on the bus by the host


controller. The host controller then polls the bus for traffic, usually in a round-robinfashion, so no function can transfer any data on the bus without explicit request fromthe host controller.

6.7.3 Host controllers

The computer hardware that contains the host controller and the root hub has aninterface geared toward the programmer which is called Host Controller Device (HCD)and is defined by the hardware implementer.

In the version 1.x age, there were two competing HCD implementations, OpenHost Controller Interface (OHCI) and Universal Host Controller Interface (UHCI).OHCI was developed by Compaq, Microsoft and National Semiconductor; UHCI wasby Intel.

VIA Technologies licensed the UHCI standard from Intel; all other chipset im-plementers use OHCI. UHCI is more software-driven, making UHCI slightly moreprocessor-intensive than OHCI but cheaper to implement. The dueling implementa-tions forced operating system vendors and hardware vendors to develop and test onboth implementations which increased cost.

During the design phase of USB 2.0 the USB-IF insisted on only one implemen-tation. The USB 2.0 HCD implementation is called the Enhanced Host ControllerInterface (EHCI). Only EHCI can support hi-speed transfers. Most of PCI-basedEHCI controllers contain other HCD implementations called ’companion host con-troller’ to support Full Speed and Low Speed devices. The virtual HCD on Intel andVIA EHCI controllers are UHCI. All other vendors use virtual OHCI controllers.

HCD standards are out of the USB specification’s scope, and the USB specificationdoes not specify any HCD interfaces.

6.7.4 Device classes

Devices that attach to the bus can be full-custom devices requiring a full-customdevice driver to be used, or may belong to a device class. These classes define anexpected behavior in terms of device and interface descriptors so that the same devicedriver may be used for any device that claims to be a member of a certain class. Anoperating system is supposed to implement all device classes so as to provide genericdrivers for any USB device. Device classes are decided upon by the Device WorkingGroup of the USB Implementers Forum.

Example device classes include:[2]

• 0x03: USB human interface device class (”HID”), keyboards, mice, etc.

• 0x08: USB mass storage device class used for USB flash drives, memory cardreaders, digital audio players etc.

• 0x09: USB hubs.

• 0x0B: Smart card readers.


• 0x0E: USB video device class, webcam-like devices, motion image capture de-vices.

• 0xE0: Wireless controllers, for example Bluetooth dongles.

USB mass-storage

A Flash Drive, a typical USB mass-storage device.

USB implements connections to storage devices using a set of standards calledthe USB mass storage device class (referred to as MSC or UMS). This was initiallyintended for traditional magnetic and optical drives, but has been extended to supporta wide variety of devices. USB is not intended to be a primary bus for a computer’sinternal storage: buses such as ATA (IDE), Serial ATA (SATA), and SCSI fulfill thatrole.

However, USB has one important advantage in that it is possible to install andremove devices without opening the computer case, making it useful for externaldrives. Today a number of manufacturers offer external portable USB hard drives,or empty enclosures for drives, that offer performance comparable to internal drives.These external drives usually contain a translating device that interfaces a drive ofconventional technology (IDE, ATA, SATA, ATAPI, or even SCSI) to a USB port.Functionally, the drive appears to the user just like another internal drive. Othercompeting standards that allow for external connectivity are eSATA and Firewire.

Human-interface devices (HIDs)

Mice and keyboards are frequently fitted with USB connectors, but because most PCmotherboards still retain PS/2 connectors for the keyboard and mouse as of 2006, aregenerally supplied with a small USB-to-PS/2 adaptor so that they can be used witheither USB or PS/2 ports. There is no logic inside these adaptors: they make useof the fact that such HID interfaces are equipped with controllers that are capableof serving both the USB and the PS/2 protocol, and automatically detect whichtype of port they are plugged in to. Joysticks, keypads, tablets and other human-interface devices are also progressively migrating from MIDI, PC game port, andPS/2 connectors to USB.


Apple Macintosh computers have used USB exclusively for all wired mice andkeyboards since January 1999.

6.7.5 USB signaling

The USB standard uses the NRZI system to encode data.USB signals are transmitted on a twisted pair of data cables, labelled D+ and

D−. These collectively use half-duplex differential signaling to combat the effects ofelectromagnetic noise on longer lines. D+ and D− usually operate together; they arenot separate simplex connections. Transmitted signal levels are 0.0-0.3 volts for lowand 2.8-3.6 volts for high.

USB supports three data rates:

• A Low Speed rate of up to 1.5 Mbit/s (187.5 kB/s) that is mostly used forHuman Interface Devices (HID) such as keyboards, mice, and joysticks.

• A Full Speed rate of up to 12 Mbit/s (1.5 MB/s). Full Speed was the fastestrate before the USB 2.0 specification and many devices fall back to Full Speed.Full Speed devices divide the USB bandwidth between them in a first-comefirst-served basis and it is not uncommon to run out of bandwidth with severalisochronous devices. All USB Hubs support Full Speed.

• A Hi-Speed rate of up to 480 Mbit/s (60 MB/s).

Though Hi-Speed devices are commonly referred to as ”USB 2.0” and adver-tised as ”up to 480 Mbit/s”, not all USB 2.0 devices are Hi-Speed. The maximumrate currently (2006) attained with real devices is about half of the full theoretical(60 MB/s) data throughput rate.[3] Most hi-speed USB devices typically operate atmuch slower speeds, often about 3 MB/s overall, sometimes up to 10-20 MB/s. TheUSB-IF certifies devices and provides licenses to use special marketing logos for either”Basic-Speed” (low and full) or Hi-Speed after passing a compliancy test and paying alicensing fee. All devices are tested according to the latest spec, so recently-compliantLow Speed devices are also 2.0.

6.7.6 USB connectors

Series ”A” plug and receptacle.


The connectors which the USB committee specified were designed to support anumber of USB’s underlying goals, and to reflect lessons learned from the variedmenagerie of connectors then in service. In particular:

• The connectors are designed to be robust. Many previous connector designswere fragile, with pins or other delicate components prone to bending or break-ing, even with the application of only very modest force. The electrical contactsin a USB connector are protected by an adjacent plastic tongue, and the entireconnecting assembly is further protected by an enclosing metal sheath. As aresult USB connectors can safely be handled, inserted, and removed, even by asmall child. The encasing sheath and the tough moulded plug body mean thata connector can be dropped, stepped upon, even crushed or struck, all withoutdamage; a considerable degree of force is needed to significantly damage a USBconnector.

• It is difficult to incorrectly attach a USB connector. Connectors cannot beplugged-in upside down, and it is clear from the appearance and kinestheticsensation of making a connection when the plug and socket are correctly mated.However, it is not obvious at a glance to the inexperienced user (or to a userwithout sight of the installation) which way round a connector goes, so it isoften necessary to try both ways.

• The connectors are particularly cheap to manufacture.

• The connectors enforce the directed topology of a USB network. USB does notsupport cyclical networks, so the connectors from incompatible USB devicesare themselves incompatible. Unlike other communications systems (e.g. RJ-45cabling) gender-changers are almost never used, making it difficult to create acyclic USB network.

• A moderate insertion/removal force is specified. USB cables and small USBdevices are held in place by the gripping force from the receptacle (without theneed for the screws, clips, or thumbturns other connectors require). The forceneeded to make or break a connection is modest, allowing connections to bemade in awkward circumstances or by those with motor disabilities.

• The connector construction always ensures that the external sheath on the plugcontacts with its counterpart in the receptacle before the four connectors withinare connected. This sheath is typically connected to the system ground, allowingotherwise damaging static charges to be safely discharged by this route (ratherthan via delicate electronic components). This means of enclosure also meansthat there is a (moderate) degree of protection from electromagnetic interferenceafforded to the USB signal while it travels through the mated connector pair(this is the only location when the otherwise twisted data pair must travel adistance in parallel). In addition, the power and common connections are madeafter the system ground but before the data connections. This type of staged


make-break timing allows for safe hot-swapping and has long been commonpractice in the design of connectors in the aerospace industry.

• The USB standard specifies relatively low tolerances for compliant USB connec-tors, intending to minimize incompatibilities in connectors produced by differentvendors (a goal that has been very successfully achieved). Unlike most otherconnector standards, the USB spec also defines limits to the size of a connectingdevice in the area around its plug. This was done to avoid circumstances wherea device complies with the connector specification but its large size blocks ad-jacent ports. Compliant devices must either fit within the size restrictions orsupport a compliant extension cable which does.

The USB (Type A and B) Connectors

Cables have only plugs, and hosts and devices have only receptacles. Hosts havetype-A receptacles; devices have type-B. Type-A plugs only mate with type-A recep-tacles, and type-B with type-B. There are several types of USB connectors, and somehave been added as the specification has progressed. An extension to USB called USBOn-The-Go allows a single port to act as either a host or a device - chosen by whichend of the cable plugs into the socket on the unit. Even after the cable is hookedup and the units are talking, the two units may ”swap” ends under program control.This facility targets units such as PDAs where the USB link might connect to a PC’shost port as a device in one instance, yet connect as a host itself to a keyboard andmouse device in another instance.

The original USB specification detailed Standard-A and Standard-B plugs andreceptacles. The first engineering change noticed to the USB 2.0 specification addedMini-B plugs and receptacles.

USB On-The-Go defined two small form factor connectors, the Mini-A and Mini-B, and a universal socket (Mini-AB) for dual host by host/device units.


A USB Series “A” plug

Micro-USB is a connector announced by the USB Implementers Forum ( USB-IF)on January 4, 2007.[4] It is intended to replace the Mini-USB plugs used in many newsmartphones and PDAs. The Micro-USB plug is rated for 10,000 connect-disconnectcycles. It is about half the height of the mini-USB connector but features a similarwidth. The Universal Serial Bus Micro-USB Cables and Connectors Specificationadded Micro-A plugs, Micro-AB receptacles, and Micro-B plugs and receptacles, alongwith a Standard-A receptacle to Micro-A plug adapter.

The Mini-B, Micro-A, Micro-B, and Micro-AB connectors are used for smallerdevices such as PDAs, mobile phones or digital cameras. The Standard-A plug isapproximately 4 by 12 mm, the Standard-B approximately 7 by 8 mm, and theMicro-A and Micro-B plugs approximately 2 by 7 mm.

Microsoft’s original Xbox game console uses standard USB 1.1 signaling in itscontrollers, but features a proprietary connector rather than the standard USB con-nector. With the introduction of the newer Xbox 360 model, Microsoft switched tothe standard USB connector. Similarly, IBM UltraPort uses standard USB signaling,but via a proprietary connection format.

The maximum length of a USB cable is 5 meters; greater lengths require hubs.[5]

USB connections can be extended to 50 m over CAT5 or up to 10 km over fiber byusing special USB extender products developed by various manufacturers.

6.7.7 Power

Mac OS X dialog displayed when a USB device requires more current than the portcan supply

The USB specification provides a 5 V (volts) supply on a single wire from whichconnected USB devices may draw power. The specification provides for no more than5.25 V and no less than 4.35 V between the +ve and -ve bus power lines. Initially,a device is only allowed to draw 100 mA. It may request more current from theupstream device in units of 100 mA up to a maximum of 500 mA.

If a bus-powered hub is used, the devices downstream may only use a total of fourunits and 400 mA of current. This limits compliant bus-powered hubs to 4 ports,among other things. The host operating system typically keeps track of the powerrequirements of the USB network and may warn the computer’s operator when agiven segment requires more power than is available.


On-The-Go and Battery Charging Specification both add new powering modes tothe USB specification.

Some USB devices draw more power than is permitted by the specification for asingle port. This is a common requirement of external hard and optical disc drives andother devices with motors or lamps. Such devices can be used with an external powersupply of adequate rating; some external hubs may, in practice, supply sufficientpower. For portable devices where external power is not available, but not more than1 A is required at 5 V, devices may have connectors to allow the use of two USBcables, doubling available power but reducing the number of USB ports available toother devices.

A number of devices use the 5 V power supply without participating in a properUSB network. The typical example is a USB-powered reading light; fans, mug heaters,battery chargers (particularly for mobile telephones) and even miniature vacuumcleaners are also available. In most cases, these items contain no digitally basedcircuitry, and thus are not proper USB devices at all. This can cause problems withsome computers - the USB specification requires that devices connect in a low-powermode (100 mA maximum) and state how much current they need, before switching,with the host’s permission, into high-power mode. An additional concern is that inaddition to limiting the total average power used by the device, the USB specificationlimits the inrush current (to charge decoupling and bulk capacitors) when the deviceis first connected; otherwise, connecting a device could cause glitches in the host’sinternal power.

There are also devices at the host end that do not support negotiation, such asbattery packs that can power USB powered devices; some provide power, while otherspass through the data lines to a host PC. There are also USB AC adapters and DCadapters that can be used to power or charge USB powered devices. Some of thesedevices can supply up to 1A of power. Without negotiation, the powered USB deviceis unable to inquire if it is allowed to draw 100 mA, 500 mA, or 1 A.

6.7.8 USB compared to FireWire

USB was originally seen as a complement to FireWire (IEEE 1394), which was de-signed as a high-speed serial bus which could efficiently interconnect peripherals suchas hard disks, audio interfaces, and video equipment. USB originally operated ata far lower data rate and used much simpler hardware, and was suitable for smallperipherals such as keyboards and mice.

About the time that the 1394a standard was reaching completion, Apple threat-ened to charge $1.00 per port to license Apple’s patents relating to 1394a (Apple hadpreviously not charged any patent royalties for 1394). This fee was considered bymany of the USB Core companies to be excessive so they started work on updatingthe USB standard to offer data rates that were competitive with 1394a. Even thoughthe 1394 patent license fee was eventually set at $0.25 per system (a price set by agroup of companies owning the ”essential patents” contained in 1394), the work onUSB 2.0 continued. Intel chose to use USB 2.0 in their chipsets rather than to requireadditional connectors to support 1394 as well as USB. Lack of 1394 support on Intel’s


chipset virtually assured that 1394 would have no significant market penetration inthe commercial PC market.

The most significant technical differences between FireWire and USB include thefollowing:

• USB networks use a tiered-star topology, while FireWire networks use a repeater-based topology.

• USB uses a ”speak-when-spoken-to” protocol; peripherals cannot communicatewith the host unless the host specifically requests communication. A FireWiredevice can communicate with any other node at any time, subject to networkconditions.

• A USB network relies on a single host at the top of the tree to control thenetwork. In a FireWire network, any capable node can control the network.

These and other differences reflect the differing design goals of the two buses:USB was designed for simplicity and low cost, while FireWire was designed for highperformance, particularly in time-sensitive applications such as audio and video.

USB 2.0 Hi-Speed versus FireWire 400

The neutrality of this article or section is disputed.Please see the discussion on the talk page.

The signaling rate of USB 2.0 Hi-Speed mode is 480 Mb/s, while the signalingrate of FireWire 400 (IEEE 1394a, the slower, yet more common variant of firewire asof 2007) is 393.216 Mb/s [6].[7] In practice, other design factors can dwarf a relativelysmall difference in signaling rate. USB requires more host processing power thanFireWire due to the need for the host to provide the arbitration and schedulingof transactions. The peer-to-peer nature of FireWire requires devices to arbitrate,which means a FireWire bus must wait until a given signal has propagated to alldevices on the bus. The more devices on the bus, the lower is its peak performance.Conversely, for USB the maximum timing model is fixed and is limited only by thehost-device branch (not the entire network). Furthermore, the host-centric natureof USB allows the host to allocate more bandwidth to high priority devices insteadof forcing them to compete for bandwidth as in FireWire.[8] USB transfer rates aretheoretically higher than FireWire due to the need for FireWire devices to arbitratefor bus access. A single FireWire device may achieve a transfer rate for FireWire 400as high as 41 Mb/s, while for USB 2.0 the rate can theoretically be 55 Mb/s (for asingle device).

In practice, FireWire 400 is generally faster than USB 2.0 Hi-Speed mode[9].USB 2.0 Hi-Speed reached a performance level sufficient for consumer equipment

while retaining compatibility with older devices. An example of how the popularityof USB displaced FireWire in a commercial device is the Apple iPod. It was originallyreleased with a FireWire connector, which was eventually modified to allow for both


USB and FireWire connections when the product was released for Windows. 3rdgeneration iPods used USB and Firewire for data transfer and only allows a FireWireconnection to charge the battery from the main adapter. The iPod does charge viaboth cables when connected to the host computer. With the 4th generation andnewer, iPods use USB for data transfer and both USB and Firewire for charging.The Firewire controller chip set has been removed in favour with reduced costs. TheiPod Nano and shuffle only support USB.[10]

Today, USB Hi-Speed is used in many consumer products. FireWire, however,retains its popularity in areas such as video and audio production.

FireWire 800 (Apple’s name for the 9-pin ”S800 bilingual” version of the IEEE1394b standard) was introduced commercially by Apple in 2003. This newer 1394specification and corresponding products allow a transfer rate of 786.432 Mbit/s.[11]

6.7.9 Version history

Hi-Speed USB Logo USB OTG Logo

• USB 0.7: Released in November 1994.

• USB 0.8: Released in December 1994.

• USB 0.9: Released in April 1995.

• USB 0.99: Released in August 1995.

• USB 1.0 Release Candidate: Released in November 1995.

• USB 1.0: Released in January 1996.Specified data rates of 1.5 Mbit/s (Low-Speed) and 12 Mbit/s (Full-Speed). Did not anticipate or pass-through monitors. Few such devices ac-tually made it to market.

• USB 1.1: Released in September 1998.Fixed problems identified in 1.0, mostly relating to hubs. Earliest revision tobe widely adopted.

• USB 2.0: Released in April 2000.Added higher maximum speed of 480 Mbit/s (now called Hi-Speed).

– Mini-B Connector ECN: Released in October 2000.Specifications for Mini-B plug and receptable. These should not be con-fused with Micro-B plug and receptable.

– Errata as of December 2000: Released in December 2000.

– Resistor ECN: Released in May 2002.

– Errata as of May 2002: Released in May 2002.


– Interface Associations ECN: Released in May 2003.New standard desriptor was added that allows multiple interfaces to beassociated with a single device function.

– Rounded Chamfer ECN: Released in October 2003.

– Unicode ECN: Released in February 2005.

• USB On-The-Go Supplement 1.0: Released in December 2001.

• USB On-The-Go Supplement 1.0a: Released in June 2003.

• USB On-The-Go Supplement 1.2: Released in April 2006.

• USB On-The-Go Supplement 1.3: Released in December 2006. This is thecurrent revision.

• MicroUSB 1.01: Released in April 2007.

• Inter-Chip USB 1.0: Released in March 2006.

• Battery Charging Specification 1.0: Released in March 2007.Adds support for dedicated chargers (power supplies with USB connectors), hostchargers (USB hosts that can act as chargers) and the Dead Battery Provisionwhich allows devices to temporarily draw 100 mA current after they have beenattached.

6.7.10 Related technologies

The PictBridge standard allows for interconnecting consumer imaging devices. Ittypically uses USB as the underlying communication layer.

The USB Implementers Forum is working on a wireless networking standard basedon the USB protocol. Wireless USB is intended as a cable-replacement technology,and will use Ultra-wideband wireless technology for data rates of up to 480 Mbit/s.Wireless USB is well suited to wireless connection of PC centric devices, just asBluetooth is now widely used for mobile phone centric personal networks (at muchlower data rates).

Powered USB uses standard USB signaling with the addition of extra power linesfor point-of-sale terminals. It uses 4 additional pins to supply up to 6A at either 5V,12V, or 24V (depending on keying) to peripheral devices. The wires and contacts onthe USB portion have been upgraded to support higher amperage on the 5V line, aswell. This is commonly used in Point of Sale applications and provides enough powerto operate stationary barcode scanners, printers, pin pads, signature capture devices,etc. This standard was developed by IBM, NCR, and FCI/Berg. It is essentially twoconnectors stacked such that the bottom connector accepts a standard USB plug andthe top connector takes a power connector.


6.7.11 References

1. USB Developers Approve Micro-USB Connector Specification, Information-Week, Jan 4, 2007

2. USB Class Codes

3. How Fast Does A USB 2.0 Drive Go On The Newest Macs? How Does ItCompare To FireWire?

4. USB Implementers Forum (2007-01-04). Mobile phones to adopt new, smallerUSB connector. Press release. Retrieved on 2007-01-08.

5. USB Frequently Asked Questions at usb.org site

6. see also List of device bandwidths#Computer buses (external)

7. choice.com.au

8. USB 2.0 vs. FireWire (English). digit-life.com. Retrieved on 19 March 2007.

9. Heron, Robert. USB 2.0 Versus FireWire. TechTV. Retrieved on 2007-04-26.

10. How Fast Does A USB 2.0 Drive Go On The Newest Macs? How Does ItCompare To FireWire? (English). Bare Feats. Retrieved on 19 March 2007.

11. FireWire vs. USB 2.0 (English). USB Ware. Retrieved on 19 March 2007.

6.7.12 External links

Wikibooks has more about this subject: Serial Programming:USB TechnicalManual

• Home of USB Implementers Forum, Inc., including the USB 2.0 specification

• USB FOR DOS

• Universal Host Controller Interface (UHCI)

• What is USB?PDF (121 KB) - Short, simple description of USB with goodpictures of cable breakdown and plugs

• Challenges of Migrating to Wireless USB - Article showing the differences be-tween USB and Wireless USB from a technical point of view

• A Mac USB 2.0 vs. FireWire comparison Speed comparison using Apple driversfor USB 2.0

• Focus on Universal Serial Bus hardware design

• USB in a Nutshell Easy to understand USB explanation targeting peripheraldesigners.

• Serial to USB converter schematic


6.8 STL (file format)

From Wikipedia, the free encyclopediaSTL (Standard Tessellation Language)[citationneeded] is a file format native to the

stereolithography CAD software created by 3D Systems of Valencia, CA, USA. STLfiles are imported and exported by many other software packages. STL files describeonly the surface geometry of a three dimensional object without any representationof color, texture or other common CAD model attributes. The STL format specifiesboth ASCII and binary representations, although binary files are more common sincethey are more compact.

An STL file describes a raw unstructured triangulated surface by the unit normaland vertices (ordered by the right-hand rule) of the triangles using a three-dimensionalCartesian coordinate system.

6.8.1 ASCII STL

An ASCII STL file begins with the line:

solid name

where name is an optional string. The file continues with any number of triangles,each represented as follows:

facet normal n1 n2 n3

outer loop

vertex v11 v12 v13

vertex v21 v22 v23

vertex v31 v32 v33

endloop

endfacet

and concludes with:

endsolid name

The structure of the format suggests that other possibilities exist (eg Facets withmore than one ’loop’ or loops with other than three vertices) but in practice, all facetsare simple triangles.

White space (spaces, tabs, newlines) may be used anywhere in the file exceptwithin numbers or words. The spaces between ‘facet’ and ‘normal’ and between‘outer’ and ‘loop’ are required.

6.8.2 Binary STL

Because ASCII STL files can become very large, a binary version of STL exists. Abinary STL file has an 80 character header (which is generally ignored - but whichshould never begin with ‘solid’ because that will lead most software to assume that this

6.8. STL (FILE FORMAT) 95

is an ASCII STL file). Following the header is a 4 byte unsigned integer indicatingthe number of triangular facets in the file. Following that is data describing eachtriangle in turn. The file simply ends after the last triangle.

Each triangle is described by twelve floating point numbers: three for the normaland then three for the X/Y/Z coordinate of each vertex - just as with the ASCIIversion of STL. After the twelve floats there is a two byte unsigned ‘short’ integerthat is the ‘attribute byte count’ - in the standard format, this should be zero becausemost software does not understand anything else.

Floating point numbers are represented as IEEE floating point numbers and theendianness is assumed to be little endian although this is not stated in documentation.

6.8.3 Colour in Binary STL

There are at least two variations on the binary STL format for adding colour infor-mation:

VisCAM/SolidView

The VisCAM and SolidView software packages use the two ‘attribute byte count’bytes at the end of every triangle to store a 15 bit RGB colour:

• bit 0 to 4 are the intensity level for blue (0 to 31)

• bits 5 to 9 are the intensity level for green (0 to 31)

• bits 10 to 14 are the intensity level for red (0 to 31)

– bit 15 is 1 if the colour is valid

– bit 15 is 0 if the colour is not valid (as with normal STL files)

Magics

The Materialise Magics software does things a little differently. It uses the 80 byteheader at the top of the file to represent the overall colour of the entire part. If colour isused, then somewhere in the header should be the ASCII string “COLOR=” followedby four bytes representing Red, Green, Blue and Alpha channel (transparency) in therange 0-255. This is the colour of the entire object unless overridden at each facet.The per-facet colour is represented in the two ‘attribute byte count’ bytes as follows:

• bit 0 to 4 are the intensity level for red (0 to 31)

• bits 5 to 9 are the intensity level for green (0 to 31)

• bits 10 to 14 are the intensity level for blue (0 to 31)

– bit 15 is 1 if this facet has its own unique colour

– bit 15 is 0 if the per-object colour is to be used (or no colour at all if the“COLOR=” string is absent from the header.


NOTE:

The red/green/blue ordering within those two bytes is reversed in these two ap-proaches - so whilst these formats could easily have been compatible the reversal ofthe order of the colours means that they are not - and worse still, a generic STL filereader cannot automatically distinguish between them. There is also no way to havefacets be selectively transparent because there is no per-facet alpha value - althoughin the context of current rapid prototyping machinery, this is not important.

6.8.4 The Facet Normal

In both ASCII and binary versions of STL, the facet normal should be a unit vectorpointing outwards from the solid object. In most software this may be set to (0,0,0)and the software will automatically calculate a normal based on the order of thetriangle vertices using the ’right hand rule’. Some STL loaders (eg the STL pluginfor Art of Illusion) check that the normal in the file agrees with the normal theycalculate using the right hand rule and warn you when it does not. Other softwaremay ignore the facet normal entirely and use only the right hand rule. So in order tobe entirely portable one should provide both the facet normal and order the verticesappropriately - even though it is seemingly redundant to do so.

6.8.5 History of use

Stereolithography machines are basically 3D printers that can build any volume shapeas a series of slices. Ultimately these machines require a series of closed 2D contoursthat are filled in with solidified material as the layers are fused together.

The natural file format for such a machine would be a series of closed polygonscorresponding to different Z-values. However, since it’s possible to vary the layerthicknesses for a faster though less precise build, it seemed easier to define the modelto be built as a closed polyhedron that could be sliced at the necessary horizontallevels.

The STL file format appears capable of defining a polyhedron with any polygonalfacet, but in practice it’s only ever used for triangles, which means that much ofthe syntax of the file is superfluous. It is also the case that the value of the normalshouldn’t be necessary, since that is a direct calculation from the coordinates of thetriangle with the orientation being controlled by the right hand rule.

STL files are supposed to be closed and connected like a combinatorial surface,where every triangular edge is part of exactly two triangles, and not self-intersecting.Since the syntax does not enforce this property, it can be ignored for applicationswhere the closedness doesn’t matter.

The closedness only matters insofar as the software which slices the trianglesrequires it to ensure that the resulting 2D polygons are closed. Sometimes suchsoftware can be written to cleanup small discrepancies by moving endpoints of edgesthat are close together so that they coincide. The results are not predictable, but itis often sufficient to get the job done.

6.8. STL (FILE FORMAT) 97

Obviously, there is much scope for “improvement” of this file format, which in itspresent form is nothing more than a listing of groups of 9 (or 12 if you care about thenormals) floating point numbers embedded in some unnecessary syntax. Since eachvertex is on average going to be used in six different triangles, considerable savings inmemory could be obtained by listing all the points in a table at the beginning of thefile, and concluding with a list of triangle definitions comprised of triplets of integersthat referenced this table.

However, for the purpose of a generating a single contour slice using a verylightweight piece of software on a computer with little memory, this format is perfectsince it can be processed in one pass regardless of file size.

6.8.6 Use in other fields.

Many Computer-aided design systems are able to output the STL file format amongtheir other formats because it’s quick and easy to implement, if you ignore the connec-tion criteria of the triangles. Many Computer-aided manufacturing systems requiretriangulated models as the basis of their calculation.

Since an STL file output, of a sorts, is almost always available from the CADsystem, it’s often used as a quick method for importing the necessary triangulatedgeometry into the CAM system.

Once it works, there is very little motivation to change, even though it is far fromthe most memory and computationally efficient method for transferring this data.Many integrated CAD and CAM systems transfer their geometric data using thisaccidental file format, because it’s impossible to go wrong.

There are many other file formats capable of encoding triangles available, such asVRML, DXF, but they have the disadvantage that it’s possible to put things otherthan triangles into it, and thus produce something ambiguous or unusable.

6.8.7 See also

• RepRap is an OpenSource project that uses STL file input and generates solidobjects as output.

• PLY (file format) is an alternative file format with more flexibility that is in usein some stereolithography applications.

• MeshLab is an open source Windows and Linux application for visualizing,processing and converting three dimensional meshes to or from the STL fileformat.

6.8.8 External links

• The STL Format - Standard Data Format for Fabbers: The STL Format.(http://www.ennex.com/ fabbers/StL.asp)


• How to Create an STL file Guide to exporting STL files from various CADpackages (courtesy of ProtoCAM) (http://www.protocam.com/html/stl.html)

• SolidView (http://www.solidview.com) SolidView is a commercial STL manip-ulation package that has a Lite version available (under provision of a businessemail address) for STL viewing.

• Freesteel (http://www.freesteel.co.uk/) with a web-interface where you can up-load an STL file and render it into an image in your browser.

• ADMesh (http://www.varlog.com/products/admesh) is a GPLed text-basedprogram for processing triangulated solid meshes, and reads and writes theSTL file format.

6.9 Xylotex: Automation, Motion Control & Robotics

Products

XylotexR©

The XS-3525/8S-4 Stepper Motor Driver Board (Ver 4.00) $185.00

• Four axis bipolar drive

• ±2.5 Amp/Phase PWM controlled drives

• up to 35 Volt (w/BEMF)

• FULL, HALF, QUARTER, & EIGHTH step/Full Step

• Built-in DC-DC Converter for 5 Volt Logic

• Filtered and Buffered STEP & DIR Signals

• Built-in Break-out:Screw Terminals for Unused Parallel Port I/O

6.9. XYLOTEX: AUTOMATION, MOTION CONTROL & ROBOTICS PRODUCTS99

• Synchronous Rectification

• Internal UVLO and Thermal Shutdown circuitry

• Easy connect for most popular Step/Direction control software

• Small Size: 5.65” X 2.85”

• Use with Mach2 (WinXP or Win2K) or TurboCNC (DOS)

This is a Four axis micro-stepping bi-polar PWM current regulated stepper motordriver. It can be configured to deliver up to ±2.5 Amps/phase up to a maximum of35 Volts (including BEMF)Each axis is independently jumper selectable to operate in either FULL, HALF,QUARTER or EIGHTH step modes. For a typical 1.8 (200 spr) stepper motor,this means up to 1,600 steps per revolution (16,000 steps per inch if driving a 10 tpilead screw). The drive is shipped in 1/8th step mode. Additional jumpers required iflower resolution wanted. Use this board for a 4 axis system, or a 3 axis system whereyou may want to add a fourth later (it is OK to just have three motors hooked up).Each axis has a potentiometer to allow maximum motor current drive adjustment.

The on-board IDC header accepts standard 26 pin IDC connectors for easy con-nection to IDC DB25 male connectors which can be directly connected to a PC’sparallel port to drive the boards STEP and DIRECTION input signals. Other un-used parallel port pin signals are routed to screw terminals for possible off-board use.(DB25 pin use – (2) Step X (3) Dir X (4) Step Y (5) Dir Y (6) Step Z (7) Dir Z,(8) Step A, (9) Dir A (18-25) GND)

Each axis has an ENA# pin to allow enabling/disabling of the motor current-drivers.

PLEASE NOTE: Althought the driver board does provide unmodified/unbufferedaccess to the unused parallel I/O through screw terminals, the board plays no otherrole in handling of home/limit switches, E-STOP, or Spindle/Coolant relay control,etc. If you want a break-out board, look here:breakout boards under hardware. Tosee a possible method of connecting switches to a drive board, look at the top of thisPAGE..

Please Read the datasheet for more information!:http://www.xylotex.com/XS3525V400.pdf

These drive boards are Fully Assembled and Tested.If you have more questions regarding using the board with your application:

Contact XylotexBefore using the device, the potentiometers must be set for proper current output,which requires the use of your voltage/multimeter! When running at High Current(generally 2.0A/phase or above), convective cooling (fan) required.You get: XS-3525/8S-4 & theIDC26-DB25 cable (IDC26-DB25 Cable is NOT aParallel port Extension cable, it connects the board to one though)

Shipping is $8.00 single board only to Continental US via USPS Priority Mail (2-3Day Service) (each additional board $2.00)


Copyright c©2005 by XylotexAll rights reservedRevised – 20-DEC-2005URL: http://www.xylotex.com

6.10 Firmware

From Wikipedia, the free encyclopediaIn computing, firmware is software that is embedded in a hardware device. It is

often provided on flash ROMs or as a binary image file that can be uploaded ontoexisting hardware by a user.

6.10.1 Definitions

A typical vision of a computer architecture as a series of abstraction layers:hardware, firmware, assembler, kernel, operating system and applications (see also

Tanenbaum 79).

Firmware is defined as:

• the computer program in a read-only memory (ROM) integrated circuit (a hard-ware part number or other configuration identifier is usually used to representthe software);

• the erasable programmable read-only memory (EPROM) chip, whose programmay be modified by special external hardware, but not by [a general purpose]application program.[1]

• the electrically erasable programmable read-only memory (EEPROM) chip,whose program may be modified by special electrical external hardware (notthe usual optical light), but not by [a general purpose] application program.

6.10. FIRMWARE 101

6.10.2 Origins

The term ”firmware” was originally used for micro-programs written for micro se-quencers such as AMD29xx. Later on, it was coined to indicate a functional replace-ment for hardware on low-cost microprocessors.

Firmware in many devices can now be updated without the need for additionalhardware, often through the use of vendor-provided software.

In practical terms, firmware updates can improve the performance and reliability,indeed even the basic available functionality of a device, and many devices benefitfrom regular firmware updates. One of the most common devices to have regularfirmware updates are recording devices such as optical media writers (DVD, CD, HDDVD, Blu-ray), as media technologies extend, so firmware updates ensure hardwareis kept up to date and compatible.

6.10.3 Evolved firmware uses

Firmware has evolved to mean the programmable content of a hardware device, whichcan consist of machine language instructions for a processor, or configuration settingsfor a fixed-function device, gate array or programmable logic device.

A typical common feature of firmware is that it can be updated post-manufacturing,either electronically, or by replacing a storage media such as a socketed memory chip.

Firmware can – but is not required to – expose an externally accessible interface.For example, in some modem implementations the firmware is not directly accessible,but is part of a combination of hardware and firmware that responds to commandsfrom the host system.

Firmware has traditionally been stored in ROM, however cost and performancerequirements have driven component vendors to adopt various replacements, includingnon-volatile media such as EEPROM and Flash, or SRAM solutions, such as thefirmware loaded by an operating system device driver, as described below.

6.10.4 Firmware and device drivers

Most devices attached to modern systems are special-purpose computers in theirown right, running their own software. Some of these devices store that software(”firmware”) in a ROM within the device itself. Over the years, however, manufac-turers have found that loading the firmware from the host system is both cheaper andmore flexible. As a result, much current hardware is unable to function in any usefulway until the host computer has fed it the requisite firmware. This firmware load ishandled by the device driver.

6.10.5 Firmware support challenges in PCs

In some respects firmware is as much a software component of a working system asthe operating system. However, unlike most modern operating systems, firmware


rarely has a well evolved mechanism for updating itself to fix bugs and addressingfunctionality issues that are detected after the unit is shipped.

The easiest firmware to update is typically the system boot-related firmware, suchas the BIOS in PCs. Some devices, such as video adapters and modems, frequentlyrely on firmware that is loaded dynamically by the operating system device driver, andthus is updated through the operating system update mechanisms entirely transparentto the user.

In contrast, storage device firmware is rarely updated with the same consistencyas other parts of the system. Further, the mechanisms for detecting firmware versionsand updating them are not standardized. As a result, these devices tend to have asignificantly higher percentage of firmware-driven functionality issues, as comparedto other parts of a modern computer system.

6.10.6 Examples

Examples of firmware include:

• The BIOS found in IBM-compatible Personal Computers;

• The platform code found on Itanium and Itanium2 systems, Intel-based MacOS X machines, and many Intel desktop boards is EFI compliant firmware;

• The operating system on a router, such as the Linksys WRT54G

• Open Firmware, used in computers from Sun Microsystems and Apple Com-puter;

• ARCS, used in computers from Silicon Graphics;

• RTAS (Run-Time Abstraction Services), used in computers from IBM;

• EPROM chips used in the Eventide H-3000 series of digital music processors.

• Adding features on the PSP

• The iPod’s control menus

• The Xbox 360 Dashboard

• The Common Firmware Environment (CFE)

• Washing Machines (WM)

• FPGA or CPLD programming files used to configure hardware for a variety ofpurposes.

6.10.7 See also

• ROM image

• Microcode

6.11. NXP SEMICONDUCTORS CORP: LPC2148 MICROCONTROLLER 103

6.10.8 References

1. Federal Standard 1037C

6.11 NXP Semiconductors Corp: LPC2148 Mi-

crocontroller

6.11.1 Introduction

The LPC214x series is the only ARM7R© microcontroller family with full USB 2.0compliance and USB.org certification. The full-speed USB 2.0 device supports 32end points with 2KB of endpoint RAM, 8KB of RAM usable by the USB DMA(LPC2146 and LPC2148 only), and all data transfer modes (Control, Interrupt, Bulkand Isochronous). These MCUs allow designers to add USB functionality to almostany end application – starting at only $3.60 for the LPC2141 (MSRP US dollarsbased on 10Kpcs). In addition to the USB 2.0 full-speed device, these low-powerMCUs have from 32KB to 512KB of zero wait-state on-chip flash, 8KB to 40KBSRAM, 10-bit ADCs, 10-bit DAC, and a low-power Real Time Clock. These small10mm x 10mm LQFP64 packaged controllers are loaded with serial communicationsinterfaces including multiple UARTs, I2C, and SPI, as well as 45 fast general purposeI/O lines.

LPC214x Chip Family.

Key Features

• 32-Bit ARM7R© Core Architecture

• Full-Speed USB 2.0 Device

• Very Fast On-Chip Flash Up to 512KB

• Up to 40KB SRAM

• 45 Fast I/O Pins with Up to 15MHz Switching

• Vectored Interrupt Controller (VIC)

• Very Small 10mm x 10mm LQFP Packaging

• Ideal for Entertainment, Connectivity, and Display Applications


6.11.2 Block Diagram

Hardware Block Diagram.

Comparison TableProduct Flash RAM ADC DAC PackagesLPC2141 32KB 8KB 1 (6 Channels) - LPFP64LPC2142 64KB 16KB 1 (6 Channels) 1 LPFP64LPC2144 128KB 16KB 2 (14 Channels) 1 LPFP64LPC2146 256KB 32KB 2 (14 Channels) 1 LPFP64

+ 8KB1

LPC2148 512KB 32KB 2 (14 Channels) 1 LPFP64+ 8KB1

1 Shared with USB DMA; See Datasheet for Details

LPC2141, LPC2142, LPC2144, LPC2146, and LPC2148 ARM7 Core MCUs

• LPC2141 Microcontroller with USB 2.0 full-speed device, 32KB ISP/IAP flash,10-bit ADC

• LPC2142 Microcontroller with USB 2.0 full-speed device, 64KB ISP/IAP flash,10-bit ADC, DAC

• LPC2144 Microcontroller with USB 2.0 full-speed device, 128KB ISP/IAPflash, 2x10-bit ADC, DAC

6.11. NXP SEMICONDUCTORS CORP: LPC2148 MICROCONTROLLER 105




Chapter 7

Assembly Tools

Here you can find all of the recommended tools for assembling your Fab@Home.

7.1 Assembly Tools for Model 1

• ARM JTAG adapter for programming your microcontroller (see the Model 1Firmware page for recommendations).

• Soldering Equipment

– Soldering Iron with fine point tip

– Solder wire - Pb-free recommended or 60/40 is fine.

– Soldering flux - look for water soluble

– Sponge for cleaning soldering iron tip

• Small slot screwdriver

• Set of Allen (hex) wrenches

– 2mm (for M2.5 metric screw)

– 2.5mm (for M3 metric screw)

– 5/64” (for #2 screw)

– 3/32” (for #4 screw)

– 7/64” (for #6 screw)

– 9/64” (for #8 screw)

• Wire stripper (combo stripper crimper tool is nice)

• Wire cutter (cutting cables)

• Small needlenose pliers with very narrow tips (for crimping and general manip-ulation)

107

108 CHAPTER 7. ASSEMBLY TOOLS

• Cigarette lighter or candle flame for sealing the ends of cable protection braid

• Hair dryer or heat-gun for applying heat-shrink tube to soldered cables

• Small vise for making ribbon cable connectors (for uniform compression of con-nector parts)

• Tape measure or yard stick for measuring cable lengths

• Masking tape, sticky labels, or a label-maker (e.g. Brother label maker) forlabeling cables and cable bundles

• Digital Multimeter (a.k.a. multimeter or electronics tester) (not essential, butrecommended)

7.2 Vendors

Radio Shack and Home Depot together can supply all of these items

Chapter 8

Styling

Here you can learn about ways of personalizing your Fab@Home, including:

• Colors of parts

• Etched logos and images on your parts

• Acrylic parts with shapes customized for style

and any other ideas you might have.

8.1 Colors of Parts

The acrylic used for the Model 1 Chassis and 1-Syringe Tool is available in a widevariety of colors, both opaque and translucent. The following vendors links describesome of the colors available:

• RP Plastics Plexiglas Acrylic

• Delvie’s Plastics Translucent 0.236” Acrylic Colors

• Delvie’s Plastics Transparent 0.236” Acrylic Colors

• Delvie’s Plastics Fluorescent 0.236” Acrylic Colors

The protective braiding is also available in a wide variety of colors. The followingpictures give a sense of the range of colors available, and were taken from:www.cableorganizer.com

Grays and Blacks

Reds

109

110 CHAPTER 8. STYLING

Yellows, Greens, Blues, and combos

8.2 Etched Logos and Images

If you have your acrylic parts cut via laser cutter, you can have logos and imagesetched onto them (at some additional expense, if you are outsourcing the parts).Etching from the back of the part makes the logos appear to float inside the part.You can have almost any image file format etched onto your parts by Koba Industriesor any sign shop or trophy shop that has laser engraving equipment.

Here you see the some of the logoswe have played with etched in mir-ror image onto the back side of theModel 1 Base Front piece.

We are experimenting with somenew graphics - the flames are cour-tesy of Jon Hiller of the CornellComputational Synthesis Labora-tory.

The Fab@Home logo and name writ large on the right side of a Model 1

8.3 Parts with Styled Shapes

If you have a clear idea of how the Fab@Home parts fit together, you can easilychange the shapes of the acrylic pieces without affecting how they assemble. This

8.4. SHOW YOUR STYLE 111

means you can drastically change the shape of your fabber, perhaps to get away fromthe bland ”Bread Box” design of the Model 1. Put cutout holes where you find themconvenient. How about sculpted flames on the chassis of your ”overclocked” fabber?

8.4 Show your Style

See the Fabbers of the World gallery page for some examples of stylish variations onthe Fab@Home design.

Please post your own fabber amongst the Fabbers of the World.If you are particularly proud of the style of your fabber, why not vie for a

Fab@Home Award for style?

112 CHAPTER 8. STYLING

Chapter 9

Model 1 Bill of Materials

Here you can find details of what you need to buy to build a standard Fab@HomeModel 1 Fabber. The majority of the parts are “off the shelf” - you can simply orderthem off the web from the recommended supplier, or find your own locally or online.The acrylic parts (“unit”) can by ordered through Koba Industries of Albuquerque,NM, USA, and a set of acrylic parts is listed as a line item in the Bill of Materialsspreadsheet below.

Alternatively, you can cut the acrylic parts yourself if you have access to a lasercutter, waterjet cutter, CNC router or mill, etc.

The current cost of all the materials as ordered from the current list of vendors isabout US$2300. If you find a better and/or cheaper alternative source for any of theparts or services, please update this list or the vendor list.

Please Note: You can also order a complete kit of parts from Koba Industriesof Albuquerque, NM, USA.

9.1 Bill of Materials Spreadsheet

Here you can find a spreadsheet listing all of the parts for a Standard Model 1 in-cluding the 1-Syringe Tool, and a set of acrylic parts from Koba Industries. Note:Bill of materials rows highlighted in yellow have changed or been added since the lastversion of the file. Note: Most people will also need to purchase an ARM JTAGadapter for programming the LPC-H2148.

9.1.1 Current Version

• Link: FAHModel1Parts-V9f.zip

• Version: 9f

• Date: 14:51, 6 April 2007 (EDT)

• Format: zip archive of Excel Spreadsheet

• Size: 12KB

113

114 CHAPTER 9. MODEL 1 BILL OF MATERIALS

• Note: Updated price and link to Koba Industries acrylic parts set for Model 1

9.1.2 Legacy Versions

• Link: FAHModel1Parts-V9e.xls.gz

• Version: 9e

• Date: 16:54, 04 January 2007 (CST)

• Format: gzip archive of Excel Spreadsheet

• Size: 12KB

• Note: Updated some obsolete part numbers to parts that are currently available

9.2 Bill of Materials

This is a summary of the information available in the spreadsheet.1. Linear Stepper Motors Package. Set of 4 Linear Stepper Motors and accessories.

Order 1 “SP 058” from HSI Inc., $610.59.Contains:

• Syringe Tool Linear Motor. Size 11 Non-captive Hybrid Linear Actuator; 5V;bipolar; 5.25inch shaft length overall; 6.68mm long M3X0.5 thread one end;0.125+/-0.001inchOD X 0.25inchL journal other end. Part No. 28F47-05-023ENGfrom HSI, Inc., $129.20.

• X Axis Linear Motor. Size 14 External Hybrid Linear Actuator; 5V; bipo-lar;13.708inch shaft length overall; 0.25inchOD X 0.000625inch (B-series) thread;1.25inchL X 0.187+/0.001inchOD journal. Part No. E35H4B-05-013ENG fromHSI, Inc., $150.00.

• Y Axis LInear Motor. Size 14 External Hybrid Linear Actuator; 5V; bipo-lar;12.878inch shaft length overall; 0.25inchOD X 0.000625inch (B-series) thread;1.25inchL X 0.187+/0.001inchOD journal. Part No. E35H4B-05-013ENG fromHSI, Inc., $145.50.

• Z Axis Linear Motor. Size 14 External Hybrid Linear Actuator; 5V; bipolar;10inch shaft length overall; 0.25inchOD X 0.00015625inch (P-series) thread;0.974inchL X 0.187+/0.001inchOD journal. Part No. E35H4P-05-010ENG fromHSI, Inc., $132.00

• X Slave Axis Lead Screw. 0.25inch OD X 0.000625inch (B-series) lead screw;14.506inch length overall; 0.187+/0.001inch OD journal both ends; 1inch and1.25inch long. Part No. LSS-025-0125A97 from HSI, Inc., $41.89.

• Additional Lead Nuts for X, Y Axes. To couple belt driven X shaft to X carriage;and to help stabilize the Y carriage (use 2 nuts). Part No. 42-195-2 from HSI,Inc., need 2, $12.00.

9.2. BILL OF MATERIALS 115

2. Nylon Zip Cable Ties; 4 inch long. Order 1 pkg of 100 ties, GL-GT-18S3, fromAction Electronics, $2.10

3. 4 Conductor Shielded 22awg cable. Cable extensions for stepper motors. Need 10feet at $0.44 per foot, JS-6152-1, from Action Electronics, $4.40

4. 2 Conductor No Shield 22awg cable. Cable for limit switches. Need 20 feet at$0.28 per foot, $5.60.

5. Flat Ribbon Cable; 26 Conductor; 28 AWG stranded; Grey. Cable connectionbetween microcontroller and amplifier/breakout board/limit switches. Order 1pkgwith a 3 foot cable, PP-F28A26G-1 26C, from Action Electronics, $0.55.

6. 24VDC Power Supply for Stepper Amplifiers. 24V; 1.67A; 40W Desktop PowerSupply; No AC cord; 3-pin IEC 320 inlet. Order 1 EPS363-ND, from Digikey,$51.08.

7. AC Power Cord; IEC 3 prong to USA 3 prong plug. 2m long; AC power cable forpower supply. Oredr 1 AE9888-ND, from Digikey, $3.52.

8. 26 Pin Ribbon Cable Male Plug. 26 pin; 2 row 0.1inchx0.1inch pitch ribbon cablemale plug connector; w/o flanges for connecting to LPC-H2148 headers. Order 2of MPK26K-ND, from Digikey, $12.32.

9. Strain relief for 26 Pin Ribbon Cable. Matching strain relief for 26 pin ribbon cableIDC connector. Order 2 of MPSR26-ND, from Digikey, $1.38.

10. Limit switch. Normally open; SPST connectorized; 51 gmf actuation; false rollersnap action switch for limit switch. Order 6 of SW884-ND, from Digikey, $12.54.

11. Cable connector for Limit Switch. JST type XA 2 position connector for Omronlimit switches. Order 1 of 455-1903-ND, from Digikey, $0.54.

12. Crimp contacts for limit switch connector. JST crimp contacts for XA connector;28-22 AWG - Need 2 per switch connector. Order 2 of 455-1904-1-ND, from Digikey,$0.68.

13. 10kOhm, bussed 9 resistor network, SIP. Soldered onto Xylotex board to pulldownlimit switches; 10kOhm; 10 pin SIP; 9 resistors; 1 end bussed to 10th pin. Order 1of 4310R-1-103LF-ND, from Digikey, $0.65.

14. USB Cable; A male to B male; 2m long. Connect PC to Fab@Home Microcon-troller. Order 1 of AE1493-ND, from Digikey, $3.89.

15. Electronics Standoff Spacers; #4-40 threaded; male/female; 0.5 inch long; alu-minum. Mount Xylotex amplifier board and Winford DB25 Breakout board to theFab@Home base rear; M-F 4-40 threaded aluminum hex 0.5 inch long. Order 28401K-ND, from Digikey, $9.38.


16. PET Braided sleeving; 1/4inch ID nominal; 10 feet. Abrasion protection andbundling of cable. Order 1 of 9284K2, from McMaster-Carr, $3.26.

17. Heat-Shrink Tubing, Black Polyolefin, Assortment Kit. Heat shrink tubing assort-ment kit used to insulate and reinforce soldered cable connections. Order 1 ofSTA-KIT-ND, from Digikey, $10.95.

18. LPC-H2148 Microcontroller Board. Philips ARM7TDMI microcontroller boardwith header connections and USB port; board MFG by Olimex. Order 1 of LPC-H2148, from Sparkfun Inc., $39.95.

19. DB25 Female to Screw Terminal break out board. Simplify wiring from Xylo-tex amplifier board to the LPC2148. Order 1 of BRK25F-R-FT, from WinfordEngineering, $19.99.

20. 4-Axis Stepper Motor Amplifier Board. Order 1 of XS3525-8S-4, from XylotexInc., $185.00.

21. SS Round Knurled Thumb Nut for Syringe Piston; M3-0.5 thread; 12mm OD;7.5mm H. Used as insert in neoprene pistons to couple to syringe tool motor shaft.Order 5 of 90368A150, from McMaster-Carr, $8.10.

22. Linear Shaft; X; Z axes. Hardened Precision Steel Shaft; 1/2inch OD; 12inch long.Order 4 6061K33, from McMaster-Carr, $33.84.

23. Linear ball bearings for X; Y axes. Self-aligning bearings seem to have too muchplay when only 1/shaft. Order 4 of 60595K73, from McMaster-Carr, $73.92.

24. Aluminum Pillow Blocks for X;Y linear bearings; 7/8inch Bore. Pillow blocks tohold fixed-aligment linear ball bearings. Order 4 of 9804K3, from McMaster-Carr,$109.80.

25. Linear Shaft; Y axis. Hardened Precision Steel Shaft; 1/2inchOD; 12inch long; 1/4-20 tapped ends; 1/2inch deep. Order 2 of 6649K2, from McMaster-Carr, $95.40.

26. Flange ball bearing for Z axis. Flange-Mount Fixed-Align Linear Ball BearingStd Length; Round Flange; 1/2inch ID; Steel Sleeve. Order 2 of 6483K53, fromMcMaster-Carr, $50.52.

27. Shaft Collar. One-Piece Aluminum Clamp-On Collar 1/2inch Bore; 1-1/8inchOutside Diameter; 13/32inch Width. Order 6 of 6157K14, from McMaster-Carr,$14.16.

28. Flange shaft supports for X Axis. Four-Bold Flange Mount Shaft Supports; for1/2inch Shaft OD; Aluminum. Order 4 of 57745K21, from McMaster-Carr, $177.64.

29. #8-32 brass threaded inserts. Brass Threaded Insert for Thermoplastics Tapered;8-32 Internal Thread; .185inch Length; Packs of 100. Order 1 of 93365A140, fromMcMaster-Carr, $9.86.

9.2. BILL OF MATERIALS 117

30. 1/4-20 brass threaded inserts; 0.3inch length. Brass Threaded Insert for Thermo-plastics Tapered; 1/4-20 internal thread; 0.3inch length; pack of 50. Order 1 of93365A160, from McMaster-Carr, $10.79.

31. #6-32 SS socket cap screw; 1/2inch length. Mounting linear bearings to acrylicsheet; etc. Order 1 of 92196A148, from McMaster-Carr, $4.89.

32. #6-32 nylon locknut; 11/64inchH; 5/16inchW. For mounting X-axis HSI externalnuts to nut flanges on XY coupling bracket. Order 1 of 91831A007, from McMaster-Carr, $5.19.

33. 1/4-20 to #6-32 Threaded Insert for Metal. For reducing tap size of Y-rail endsfrom 1/4-20 to #6-32 for mounting to X linear bearing pillow blocks. 9/32inchlong - rail is tapped 1/2inch deep. Order 1 of 90248A017, from McMaster-Carr,$6.75.

34. #6-32 SS socket cap screw; 1inch length; partial thread. Fastening Z-axis HSIExternal Nut to Z-Carriage. Order 1 of 92196A153, from McMaster-Carr, $5.94.

35. #8-32 SS socket cap screw; 3/4inch length. Mounting X rail flange mounts tobase walls; for belt tensioner, and mounting Z-table to Z-Carriage. Order 1 of92196A197, from McMaster-Carr, $5.67.

36. 18-8 Stainless Steel Flat Washer 8 Screw Size, 11/64inch Id, 3/8inch Od, .024inch-.038inch Thk. Mounting the Z table to the Z carriage; prevent stress cracks inZ-Table Support Cross from spring forces associated with leveling the table. Order1 of 92141A009, from McMaster-Carr, $1.72.

37. M3-0.5 SS socket cap screw; 10mm length. Mounting X; and Y linear motors to0.25inch acrylic. Order 1 of 91292A113, from McMaster-Carr, $6.32.

38. M3-0.5 SS socket cap screw; 40mm length. Mounting Z linear motor under 0.25inchacrylic. Order 1 of 91292A024, from McMaster-Carr, $8.42.

39. #8-32 SS socket cap screw; 1inch length. Mounting Z flange bearings to 3-layerstack for Z-table. Order 1 of 92196A199, from McMaster-Carr, $6.65.

40. M3 SS washers; 9mmOD; 0.7mm thick. HSI Motor mounting to acrylic sheet.Order 1 of 91116A120, from McMaster-Carr, $1.80.

41. #6-32 SS Hex Nut; 7/64 thick; 5/16 OD. Tab/Notch assembly for acrylic sheetparts in tight location - esp. on Z table around flange bearings. Order 1 of91841A007, from McMaster-Carr, $2.90.

42. #4-40 SS socket cap screw; 1/2inch length. Tab/Notch assembly for acrylic sheetparts of syringe tool and Y-carriage; mounting electronics to base rear. Order 1 of92196A110, from McMaster-Carr, $3.97.


43. #4-40 hex nut; 3/16inch W; 1/16inch H. Tab/Notch assembly for acrylic sheetparts of syringe tool and Y-carriage. Order 1 of 90730A005, from McMaster-Carr,$3.48.

44. #6-32 SS socket cap screw; 3/4inch length. Mounting syringe tool to Y carriage;and attaching Y rails to X linear bearing pillow blocks. Order 1 of 92196A151,from McMaster-Carr, $5.06.

45. #6-32 Brass Threaded Inserts; 0.150inch Length. On the Z carriage; Y carriageand XY coupling plates to allow attachment of acrylic pieces to linear bearingpillow blocks or to lead nuts. Order 1 of 93365A130, from McMaster-Carr, $8.72.

46. #6-32 SS socket cap screw; 5/8inch length. For various assembly; especially acrylicsheet-edge to square nut assembly. Order 1 of 92196A150, from McMaster-Carr,$4.95.

47. #6-32 Flat Square Nut; Steel; 5/16inch OD; 7/64inch thk. Tab/Notch assemblyfor acrylic sheet parts. Order 1 of 94855A115, from McMaster-Carr, $1.06.

48. Wave spring washers; 0.194inch ID; 0.242inch OD; 0.0057inch thk. Bearing spacingfor pulleys and shaft collars on X; Y; Z lead screws. Orde 1 of 9714K22, fromMcMaster-Carr, $8.06.

49. Compression Spring; 302 SS; 3/8””H x 0.24””OD x 0.196””ID; 10.lb/inch. Forbuild surface leveling; used as counter force to screws holding table to Z carriage.Order 5 of 9435K35, from McMaster-Carr, $4.58.

50. M2.5X0.45 SS Socket Cap Screw; 8mm length. For mounting Syringe Tool Motorsto Syringe Tool. Order 1 of 91292A012, from McMaster-Carr, $11.85.

51. Rubber Foot; 1/4-20 X1/2inch thread; 1inch diameter 25lb rated. Rubber feet forsystem. Order 1 of 9377K53, from McMaster-Carr, $5.82.

52. 1/4-20 SS Hex Nut; 7/16inch W; 3/16inch H. To space rubber feet. Order 1 of91841A029, from McMaster-Carr, $6.23.

53. #2-56 X 5/8inch SS socket cap screw. Screws for mounting the limit switches toacrylic sheet parts. Order 1 of 92196A083, from McMaster-Carr, $7.10.

54. #2-56 SS hex nut. For mounting the limit switches to acrylic sheet parts. Order 1of 91841A003, from McMaster-Carr, $2.85.

55. Clear Acrylic Sheet Parts; 0.234inch thick; 1 set. 1 Set of Laser Cut Clear AcrylicSheet Parts for a Fab@Home kit base unit; 1-syringe tool; and build surface. Order1 set from Koba Industries, $410.00.

56. Aluminum Shaft Collar for Syringe Tool Motor. Used to prevent rotation of non-captive syringe tool motor shaft. Order 1 of 9946K41, from McMaster-Carr, $0.81.

9.3. ACRYLIC PARTS 119

57. #6-32 SS socket cap shoulder screw. Used to prevent rotation of non-captive sy-ringe tool motor shaft;18-8 Ss Precision Hex Socket Shoulder Screw 5/32”” Shoul-der Dia; 1/2”” L Shoulder; 6-32 Thread. Order 1 of 94035A529, from McMaster-Carr, $2.64.

58. Ball bearings for HSI motors free ends and belt tensioner. Ball-bearing ABEC5;double shield; flanged; for 0.1875inch OD shaft. Order 7 of 57155K321, fromMcMaster-Carr, $42.63.

59. SS303 Shaft; 0.1872inch OD; 1.75inch long for Belt Tensioner. Stainless steel shaftfor belt tensioner; 0.1872+/-0.001inch OD X 1.75inch. Order 1 of “A 7X 1-06017”,from SDP-SI, $1.87.

60. Timing belt to couple x-drives. Timing Belt; Pitch Length 29inch; Urethane/Kevlar;3/8inch. Order 1 of “A 6B 3-145037”, from SDP-SI, $9.10.

61. Timing pulleys to couple x-drives. Timing Pulley; 0.2 XL Pitch; 0.375inch belt;Fairloc hub; PD 0.828inch. Order 3 of “A 6H 3-13DF03706”, from SDP-SI, $33.36.

62. Shaft collar for HSI motors free ends. Stainless Steel Set-screw Shaft Collar. Order3 of “A 7X 2-11406”, from SDP-SI, $17.37.

63. Syringe Barrel, 10cc clear polyethylene syringe barrel; luer tip. Order 1 of “5111LL-B”, from EFD Inc., $20.22.

64. Syringe Piston; Neoprene; 10cc. Black neoprene rubber pistons for use with 10ccsyringe barrels. Order 1 of “5111S-B”, from EFD Inc., $15.54.

65. Syringe Tip Sampler Kit. A kit with a wide variety of different tips; tip caps; endcaps; some other piston types. Order 1 of “5100”, from EFD Inc., $42.34.

66. Binder Spring Clip Steel, 3/4” Width, 5/16” Jaw Opening. Paper clamps to securewax paper/foil to build surface. Order 1 of “12755T72”, from McMaster-Carr,$0.64.

67. Wax Paper: Attach to build surface to allow easy removal of finished parts. Buy aroll for $2 at the Grocery store.

68. GE #103 Silicone RTV black- starter material. A 2.8oz tube of GE 1-part silicone,black, as a first material to try out - begins curing in 20 minutes. A 2.8oz tubeof GE 1-part silicone, black, as a first material to try out - begins curing in 20minutes. Order 1 tube of “7545A661”, from McMaster-Carr, $3.27

9.3 Acrylic Parts

Below you can find files in several CAD formats which describe the acrylic parts. Eacharchive should contain part files and an Excel spreadsheet which describes quantitiesof each part, recommended material, and recommended orientation for parts during


the cutting process - the orientation affects the ease of assembly because many cuttingprocesses leave slightly tapered cuts.

Archives described as “Nominal Dimensions” show the parts with the exact di-mensions they should have once you have them in hand. Archives described as “Offsetby . . . for . . . ” have had the dimensions altered to compensate for effect of materialremoved by a cutting process so that the parts will end up with nominal dimensionswhen cut with the specified process.

Notes to Solidworks users:

1. SolidWorks Parts files REQUIRE INCH UNITS; parts contain equations whichare unit dependent

2. The primary part configuration (with long descriptive name) represents the partwith nominal dimensions.

3. Configuration named “Cut Compensated” is automatically offset to compensatefor tool kerf according to the global variable “Cut Compensation Offset” (see“Equations”)

4. “Cut Compensation Offset” is the one-sided offset of the part boundaries; e.g.should be set equal to 1/2 of the total width of cut associated with your process.

5. To generate drawings offset for your machining process, activate the “Cut Com-pensated” configuration, and adjust the “Cut Compensation Offset” variable.

6. Please cut parts with recommended part view facing (up) toward laser; kerfflare used to assist assembly

For Solidworks

• Link: Model1Acrylic-SLDPRT-Nominal.zip

• Version: 9

• Date: 18:03, 17 October 2006 (EDT)

• Format: zip archive of SolidWorks 2005 SLDPRT files

• Size: 23MB

• Note: Solidworks part files for the acrylic parts of the Model 1. Parts are innominal dimension configuration, but also have a derived “Cut Compensated”configuration tied to an equation variable “Cut Compensation Offset” whichcan be used to automatically offset the parts for manufacturing processes.


Additional File Formats

• STEP

• DWG

• DXF

• Parasolid

• IGES

9.3.1 Offset by 0.0055” for 35W Epilog Helix Laser Engraver

For Solidworks

• Link: Model1Acrylic-SLDDRW-0055in-Helix35W.zip

• Version: 9

• Date: 14:17, 6 April 2007 (EDT)

• Format: zip archive of SolidWorks 2006 SLDDRW “detached”(unlinked) draw-ing files

• Size: 2MB

• Note: drawing files are layouts of acrylic parts for Model 1 on five 24” × 18”sheets (Sheet1-5) and two 12” × 12” sheets (1 Syringe Tool, Z Table). Partshave been offset 0.0055” for cutting on an Epilog Helix 35W laser engraver; alsoincluded are a front and a side layout including etchable logos.

Layout DXF Files

• Link: Model1Acrylic-DXF-0055in-Helix35W.zip

• Version: 9

• Date: 14:17, 6 April 2007 (EDT)

• Format: zip archive of DXF drawing files

• Size: 433kB

• Note: files are layouts of acrylic parts for Model 1 on five 24” × 18” sheets(Sheet1-5) and two 12” × 12” sheets (1 Syringe Tool, Z Table). Parts have beenoffset 0.0055” for cutting on an Epilog Helix 35W laser engraver; also includedare a front and a side layout including etchable logos.


9.3.2 Offset by 0.0000” (nominal size) for Waterjet cutting

Layout DXF file

• Link: Chassis48by24DXF.zip

• Version: 9

• Date: November, 2006

• Format: zip archive of DXF files

• Size: 101kB

• Note: This Zip file contains two DXF layouts in inches for the complete set ofacrylic parts for a Model 1, on two 48”×24” acrylic sheets including an extra Ztable. Also, there is a scrap left from Sheet2 which is sufficient in size for thesyringe acrylic parts (larger than 6”×12”)

9.3.3 Offset by 0.0035” for 85W Laser Cutter (Koba Indus-

tries)

For Solidworks

• Link: Model1Acrylic-SLDPRT-0035in-Koba.zip

• Version: 9

• Date: 14:17, 6 April 2007 (EDT)

• Format: zip archive of SolidWorks 2005 SLDPRT files

• Size: 23MB

• Note: Solidworks part files for the acrylic parts of the Model 1. Parts havea nominal dimension configuration, but are saved in a derived ”Cut Compen-sated” configuration tied to an equation variable ”Cut Compensation Offset”,which has been set to 0.0035” for cutting by a 85W laser cutter - e.g. at KobaIndustries.

9.4. VENDORS 123

9.4 Vendors

9.4.1 Preferred Vendors (tested)

Name URL/Contact Category DetailKoba Indus-tries

http://www.kobask8.com,Kenji Kondo KenjiKondo

Mechanical Acrylicparts forFab@Home,FullFab@Homekits!

McMaster-Carr Indus-trial Supply

http://www.mcmaster.comMechanical Mechanicalcomponents,raw materials,fasteners,industrialsupply

Stock DriveProducts

http://www.sdp-si.com Mechanical Positioningand trans-missioncomponents

HaydonSwitch andInstrument

http://www.hsi-inc.com,Joe Rossi, AnnmariePelcher,+1(203)756-7441

Electrome-chanical

Linear step-per motors

Xylotex Inc. http://www.xylotex.com Electronics Stepper mo-tor amplifierboards

Winford En-gineering Inc.

http://www.winford.com Electronics Cables,breakoutboards,adapters


Name URL/Contact Category DetailSpark FunInc.

http://www.sparkfun.com Electronics LPC-H2148Microcon-trollers (andother), JTAGprogrammers,cool stuff!

DigiKey http://www.digikey.com Electronics The one andonly! - ul-timate sourcefor electronicsstuff

Action Elec-tronics

http://www.action-electronics.com

Electronics Cable andwire (includ-ing ribboncable) by thefoot, othercables

Rowley Asso-ciates

http://www.rowley.co.uk Software, Em-bedded Devel-opment

RowleyCrossWorksfor ARMEmbeddedDevelop-ment Suite,USB JTAGinterface

EFD Incorpo-rated

http://www.efd-inc.com/components.html,1(800)556-3484,1(404)434-1680

Fluid Dis-pensingEquipmentand Supplies

Syringe bar-rels, pistons,nozzles andneedles;completedispensingsystems

9.4. VENDORS 125

9.4.2 Alternative Vendors (untested)

Name URL/Contact Category DetailBoston Lasers www.bostonlasers.com,

Vadim Daskal,+1(781)569-6216

ContractManufactur-ing

Laser cuttingof acrylicparts forFab@Home

Ridout Plas-tics

www.rplastics.com/index.html, +1(858)560-1551

Acrylic SheetMaterials,ContractManufactur-ing

Acrylic sheetvendor, andlaser cuttingof acrylicparts

LaserAZ,LLC

www.laseraz.com ContractManufactur-ing

Laser cuttingof acrylicparts orcardstocktemplates

MSC Indus-trial Supply

www1.mscdirect.com Mechanical Mechanicalcomponents,raw materials,fasteners,industrialsupply

MicroControllerPros Corpo-ration

microcontrollershop.com Electronics LPC-H2148Microcon-troller board(and otherµC’s), etc.

Mouser Elec-tronics

www.mouser.com Electronics Another greatelectron-ics supplycompany

I&J Fisnar In-corporated

www.ijfisnar.com,1(201)796-1477

Fluid Dis-pensingEquipmentand Supplies

Syringe bar-rels, pistons,nozzles andneedles;completedispensingsystems


Chapter 10

Model 1 Cables

This chapter teaches you how to make all of the cables for the Fab@Home Model 1.

10.1 Power Supply Cable

The Elpac power supply provides 24 volts DC for the stepper motor amplifier. TheXylotex amplifier board power connection is via screw terminals, while the powersupply cable terminates with with a power jack. The connector needs to be removed,and the power cable sheath stripped, and the conductors stripped and tinned.

The Elpac power supply has a connec-tor, but the Xylotex amplifier has screwterminal connections for power

Cut the connector off of the Elpacpower supply cable

127

128 CHAPTER 10. MODEL 1 CABLES

Strip the cable sheath back about 1” Strip and tin the conductors

10.2 Cable Extensions for HSI Motors

The HSI Size 14 External Motors forthe X, Y, Z axes (left to right) ofthe Model 1 Chassis, with pieces of 4-conductor cable for extensions

The HSI Size 11Non-captive Motorfor the Model 11-Syringe Toolwith a length of4-conductor cablefor extension

The HSI Motors come prewired with 12” long leads, colored red, red-white stripe,green, green-white stripe. You will need to extend the prewired leads by soldering onextensions using 4 Conductor Shielded 22awg cable. Each motor requires a slightlydifferent length of extension to allow it to reach to the amplifier board while allowingenough slack for motion. In the table below, you can find the recommended extensionlengths for the X, Y, and Z motors, and for the 1-Syringe Tool motor. Total lengthis measured from the body of the motor, extension length is the addtional amountof cable required, and is the total length less the 12” long prewired leads on the

10.3. CABLES FOR LIMIT SWITCHES 129

motors. For details on how to prepare the motor cable extensions, see: AssemblyTips:Soldering Motor Cable Extensions

Model 1 Motor Cable Extension LengthsMotor Total Length Extension Length

X Motor 32 inch 20 inchY Motor 35 inch 23 inchZ Motor 25 inch 13 inch

1-Syringe Tool Motor 52 inch 40 inch

10.3 Cables for Limit Switches

Examples of two of the six limit switches with prepared cables

The Model 1 design includes 6 limit switches for the chassis motion axes, 2 peraxis. The limit switches on the Model 1 provide a signal to the microcontroller whenthe axes have moved as far as they can. The microcontroller can then stop trying tomove that axis, preventing damage to the hardware. You need to make some cablesto connect the limit switches to the microcontroller (via the amplifier board). Hereyou can find the recommended length of cable to make for each switch. You shoulduse the ”2 Conductor No Shield 22awg” cable for this purpose. The limit switchsimply breaks a circuit, so it does not matter which color of conductor from the cableconnects to which pin of the switch. For details on how to prepare the cables, see:Assembly Tips:Making Limit Switch Connectors

Limit Switch Cable LengthsSwitch Axis Location Cable Length

X Front 31 inchX Rear 23 inchY Left 52 inchY Right 52 inchZ Top 30 inch

Z Bottom 11 inch


10.4 Ribbon Cables

There are three ribbon cables required for the Model 1. These are:

A DB25 to IDC26 ribbon cable, pro-vided by Xylotex with the XS-3525/8S-4 Amplifier board, and used to connectthe XS-3525/8S-4 26pin header to theDB25 connector on the Winford Engi-neering DB25 breakout board

Two identical IDC26 ribbon cables thatyou will need to make to connect theLPC-H2148 microcontroller board tothe Winford DB25 board

To prepare these two ribbon cables, proceed as follows:

Step 1:Cut two 9” long pieces of26 conductor ribbon cable, and orientthem as shown, red stripe to right (orfirst brown conductor to right, if youare using rainbow colored cable)

Step 2:Make an IDC connector on theend of each piece of ribbon cable, asdescribed in “Assembly Tips for IDCConnectors,” and label the cables asIDC26 #1 and #2 - to keep them dis-tinct

10.5. AMPLIFIER ENABLE CABLE 131

Step 3:On the free ends (opposite theIDC connectors), peel apart the indi-vidual conductors of the ribbons forabout 3”. You will need to access indi-vidual conductors to make connectionsto the screw terminals on the WinfordDB25 breakout board.

Step 4:Referring to the ElectronicsSchematic, strip and tin the appro-priate conductors of the ribbon ca-bles to make the connections betweenthe LPC-H2148 and the Winford DB25breakout board. Note the orientationof the cables - start counting from theright (which should be the red conduc-tor on grey ribbon) with the connectordown and connector pins facing you.

10.5 Amplifier Enable Cable

Updated: 14:59, 4 May 2007 (EDT)

Note that amplifier enables require firmware version 3.

Because stepper motors have a constant current running through them duringoperation, they can become quite hot. The Xylotex amplifier board has an electronicinterface which allows an external device to enable/disable the amplifiers on demand,and here we will make a cable which will allow the LPC-H2148 to shut off the amplifierwhen it is sitting idle.


Step 1:In its factory configuration, theXylotex board has all of the amplifieraxes enabled via jumpers (small blackconnectors which short two pins to-gether). Using needle nose pliers, re-move (but keep) the amplifier enablejumpers from all 4 axes of the board.

Step 2:From the extra ribbon cableleftover from above, peel off 2 strands,and cut them to 4” (100mm) in length.You will also need two of the jumpersthat you removed from the Xylotexboard in Step 1.

Step 3:On one end of your cable, splitthe two strands for about 20mm, andstrip the ends back about 2mm, and tinthem.

Step 4:On the other end of the cable,strip both strands back about 4mm,then twist them together, and tin themtogether.

10.6. BUNDLING AND ROUTING THE CABLES 133

Step 5:Now solder each of the splitstrands to one of the jumpers. Thejumpers have an exposed metal tabthat is convenient for soldering.

Step 6:Your completed cable shouldlook like this.

10.6 Bundling and Routing the Cables

Here you will see some recommendations for protecting, organizing, and routing thevarious cables of your Fab@Home Model 1. The Model 1 Bill of Materials includespolyester braiding, which is a loosely woven tube of polyester. When squeezed longitu-dinally, this braiding will expand to many times its relaxed diameters, allowing you fitseveral cables inside. The braid then relaxes down around the cables, grouping themand protecting them from abrasion. For help with cutting, sealing, and threadingcables through braiding, see: Assembly Tips:Using Protective Braiding

Braid Lengths, and Cable Bundling

Bundle Name Cables in Bundle Braid Length(relaxed)

X Bundle X-axis motor cable, X-front limit switch 31 inchesZ Bundle Z-axis motor cable, Z-top limit switch 30 inch

Y Carriage Y-axis motor cable, 52 inchBundle Y-left and Y-right limit switches

1-Syringe Tool Syringe tool motor 52 inch

Note:The above lengths provide the simplest bundling process. If you would liketo conserve braid and/or more tightly bundle your cables, you can bundle the X, Y,and Z bundles together in the same braid by passing cables through the wall of thebraid at branching points, and cutting shorter pieces to cover the ends past branchingpoints.

The Model 1 Chassis has a number of holes provided for routing the various cables,and also for zip-tying the cables to various points on the carriages and chassis to securethem.


In this image you can see all of thecable bundles routed and secured withzipties on the machine. Note the sub-stantial loops of the cable bundles toallow for motion of the axes withoutexcessive bending of the cables. Thisreduces wear on the cables, prolongingtheir life.

Here you can see the origin of the YBundle and 1-Syringe Tool bundle atthe Y carriage. The braid for Y LimitSwitch cables is secured with ziptiesright at the cable connectors. A shortpiece of braid is used to protect one ofthe limit switch cables until it can forma junction with the full length of braidused for the Y Bundle. Secure the YBundle with a ziptie to one of the holesprovided in the side plates of the Y-carriage, as shown. The braid for the 1-Syringe Tool bundle should be securedto the back of the 1-Syringe Tool bodywith a ziptie as shown.

10.6. BUNDLING AND ROUTING THE CABLES 135

Here you see the origin of the X Bundleat the X axis motor. Note how the bun-dle is routed through the holes in thefront face and top of the machine base.The X-Front Limit Switch cable entersthe bundle just behind the X-motor.

Observe that the 1-Syringe Tool bun-dle is kept essentially separate from theother bundles. This simplifies changingtools in the case that you are consider-ing working with more than one depo-sition tool. Note also how the X-RearLimit Switch Cable enters the XYZ-Combined Bundle near the routing holein the rear of the machine base. Thisis a more aggressive bundling schemein which the X,Y, and Z bundles arepacked into the piece of braid used forthe X Bundle. This reduces the overallamount of braid required, but adds thecomplication of more junctions in thebraid.


All of the cable bundles pass through a hole in the upper part of the back plate ofthe machine base. Use zipties to group them together to keep them neat.

Chapter 11

Assembly Tips

This chapter gives hints, tips, and tricks to make assembly of your fabber easier, andto improve the quality of your completed fabber.

11.1 Threaded Inserts for Thermoplastics

The Model 1 uses threaded brass thermoplastic inserts to put strong threads into theacrylic parts for bolting parts together. These inserts need to be "melted" into theacrylic, using a soldering iron. Generally, the laser cut acrylic pieces will have a facewith sharper edges - the DOWN FACE - which was laying down, facing away fromthe laser during cutting, and a face with more rounded edges - the UP FACE - whichfaced toward the laser during cutting. Unless otherwise specified, you should insertall threaded inserts into the face with more rounded edges. This will make insertioncleaner (less melted plastic will accumulate around the insert) and easier (the insertwill fit partially into the hole from the UP FACE, but not so from the DOWN FACE).Below you can find a detailed explanation of the recommended method for insertingthese brass threaded inserts:

NOTE: Try to screw in a bolt after melting the inserts into the acrylic. Firstoff, it will allow you to see whether your insert is squared up with the face of theacrylic. Secondly, you will be able to see whether any acrylic melted in such a wayas to interfere with the screw. Usually, any melted acrylic in the way can be easilyremoved before the brass insert cools. (I’ll try to get some pictures of this up ASAPPkiddy 22:25, 13 November 2006 (EST))

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138 CHAPTER 11. ASSEMBLY TIPS

Step 1: Orientation - The threadedbrass inserts have a slightly taperedshape (right) to guide it into the hole.The direction of insertion for the inserton the right of the photo would be to-ward the bottom of the image (the re-ceiving hole would be below the insert).

Step 2: Place in hole - The insertsshould fit slightly into the appropriateholes.

Step 3: Position the part and sol-dering iron - Hold or clamp the partsuch that the hole for the insert is over-hanging the edge of your workbench,and insert the tip of a hot soldering ironinto the insert.

Step 4: Insertion - Use gentle pres-sure from the soldering iron to pushthe insert straight downward into theacrylic part.

11.1. THREADED INSERTS FOR THERMOPLASTICS 139

Step 5: Steering - Use the solder-ing iron to steer the insert to keep itstraight in the hole as you insert it.

Step 6: Depth (front) - Continuepushing the insert until it is just flushwith the upward facing surface of theacrylic. There will be a small ridgeof melted acrylic which rises slightlyabove the insert.

Step 7: Depth (rear) - Ensure thatthe insert does not protrude beyond theback side of the acrylic - the back sur-face must remain flat to align correctlyagainst other parts.

Step 8: Check Angle - Use a screwof the proper size to see how wellyour threaded insert is positioned. Ifcrooked (like the one shown), take thescrew out and use the soldering iron toadjust the insert (alternatively, the in-sert may still be hot enough that youcan use the screw to push it into theproper position).

Another Idea to insert the brass would be to use a drill press with a straight rodin the chuck that has a tip ground on it. With the metal rod in the drill press youcould add heat to the rod while gently adding pressure straight down to prevent sideto side twist. This is with the drill off and not spinning


11.2 Stripping Cable and Wire

Step 1: Cutting the sheath - Us-ing your wire stripper, or a knife, gen-tly cut partially into the outer sheath(gray in photo) of the cable about 1inch (25mm) from the end. Be carefulto not cut too deeply - we want to avoiddamaging the (red/black in photo) in-sulation on the individual conductorsinside!

Step 2: Removing sheath - Bendthe cable sharply at the location of yourcut to break the sheath, and pull it off.This can take a bit of effort and someslight additional cutting of the sheath.

Step 3: Stripping wire - Using yourwire stripper, wire cutters, or a knife,gently cut into the conductor insula-tion about 1/4 inch (6.4mm) from theend. Be careful not to cut too deeplybecause slight cuts into the copper con-ductors will cause them to break off. Asyou cut into the insulation, you shouldfeel a slight change in firmness whenyou reach the copper.

Step 4: Removing insulation - Pullthe insulation off of the wire and lookclosely for nicks (cuts) into the copper.If you cut the copper, you should cutoff the wire before the nick, and stripthe insulation back further. If you areworking with multi-strand wire, twistthe exposed copper strands tightly to-gether.

11.3. TINNING STRIPPED CONDUCTORS 141

11.3 Tinning Stripped Conductors

Tinning of stripped copper wire protects it from corrosion and improves electrical con-ductivity and ruggedness of connections between stranded conductor cables and otherdevices. It also makes the soldering of extensions to cables (wire to wire soldering)much easier.

Step 1: Apply flux - Apply a smallamount of soldering flux to the barecopper. We recommend using a no-clean flux.

Step 2: Apply solder - With yoursoldering iron, heat the stripped copperfor a 3-5 seconds. Touch the solder wireto the hot copper, and let the solderflow to cover the copper.

11.4 Soldering Motor Cable Extensions

The HSI motors come with 12" (30cm) wire leads - 4 wires, in the colors red, red-white,green, green-white. These need to be extended to reach the amplifier board. Here wewill extend them by soldering on a length of 4-conductor cable. It is important to usecable with "stranded conductors" in which each of the 4 copper conductors is actuallymade of many fine copper strands twisted together. Stranded conductors can bendmore easily and can tolerate being bent many times before breaking - important foruse in moving machines. Solid copper conductors, such as those used for householdwiring, would break after only a few times being bent. The recommended lengths ofcable extension are quite long so that the cable is not bent sharply by the motion axes- this also prolongs the life of the cable. Because many of the cables will be movingwith their respective axes, it is recommended that you protect them from abrasionwith Protective Braiding. The braiding will also allow you to bundle related cablestogether (e.g. Y limit switch cables with Y motor cable), keeping your system neatand organized.


Step 1: Prepare motor extensioncable- Using the lengths recommendedfor your fabber model, cut a length of4-conductor cable to extend the motorleads for each motor. Strip the cableand conductors on both ends of eachextension, and tin the stripped conduc-tors on both ends (see Stripping Cableand Wire and Tinning Stripped Con-ductors).

Step 2: Prepare and secure mo-tor leads - The HSI motor leads arepre-stripped to about 1 inch (25.4mm).Twist the conductors of each lead wiretightly together, and cut them off toabout 1/4" (6.35mm). Apply flux andtin them. Find heat shrink tubing (yel-low in photo) with a slightly larger di-ameter than the motor leads (we rec-ommend 0.076" to 0.093" ID tubing).Cut four pieces about 1" long, andthread them on the motor leads. Se-cure the motor leads to block of woodas shown in the order red, red-white,green, green-white. Laying them out inthis order will simplify connecting themotor to an amplifier, and taping themdown to a wood block frees your handsfor soldering.

11.4. SOLDERING MOTOR CABLE EXTENSIONS 143

Step 3: Position and secure theextensions - Secure the tinned con-ductors of the extension right next tothe tinned motor leads. Pay attentionto the color sequence you choose to use(write it down!) so that you knowwhich color in the extension corre-sponds to which motor lead color - thiswill simplify connecting the motor tothe amplifier. We recommend red=red,red-white=black, green=green, green-white=white.

Step 4: Solder the conductors - Us-ing the side of the tip of your solder-ing iron, press the tinned ends of theconductors against each other until thesolder on them from tinning begins tomelt. Add a small amount of solderto make a nice smooth connection. Toprevent the wires springing apart whenyou remove the soldering iron, you mayneed to hold them down with a finger(caution - they will be hot!) or a tool.Blowing on them will freeze the solderquickly.

Step 5: Slide the shrink tube -Once the solder joints are all made andhave cooled, slide the heat shrink tubepieces up over the solder joints.

Step 6: Shrink the shrink tube -Using a heat gun or a hair-dryer, heatup the shrink tube until it contractsuniformly onto the solder joint. Thisprotects the joints from corrosion andshorting with each other.


Step 7: Examine your work - Take a moment to examine the joints for quality.There should be no sharp solder points poking through the shrink tube, and thetube should be tight, and not free to slide around on the wire. Being careful atsteps like these will make for a much more reliable machine later, saving a lot of

time and trouble in repairs.

11.5 Making IDC Ribbon Cable Connectors

IDC or Insulation Displacement Connectors are very simple to make. The connectorsare designed with sharp forked contacts which cut through the insulation of theribbon cable to make contact with each of the conductors inside. You simply needto make sure that you align the cable properly and apply uniform force to squeezethe connector parts together. A vice is recommended for this, but in the absence ofa vice, vice grips or large pliers can be used, but protect the connectors with thinpieces of wood or metal to distribute the plier force.

11.5. MAKING IDC RIBBON CABLE CONNECTORS 145

Step 1: Gather parts - Using sharpscissors, cut the ribbon cable straightacross to the length recommended bythe assembly instructions for your fab-ber model. Look at the cut end toensure that the conductor strands arecleanly cut, and have not been pulledout or made to touch each other. TheIDC connector will usually consist of 3parts - the connector front, the connec-tor back, and a strain relief clip (seephoto).

Step 2: Orient correctly - For theModel 1 you need to orient the con-nectors carefully so that the connec-tions between the microcontroller andother electronics can be made correctly- you will need to select certain individ-ual conductors in the ribbon by count-ing from one edge, and that edge mustbe oriented correctly to ensure thatthe conductors you select connect tothe correct microcontroller pins. Thephoto shows the correct orientation forboth connectors for the Model 1. Notethe position of the notch in the con-nector front, and the red stripe on theribbon cable.


Step 3: Expose connector backadhesive - Peel the paper off of theconnector back, exposing the adhesive.Be careful to not peel the adhesive off.Note the scalloped surface beneath theadhesive, which is used to align the rib-bon cable against the connector back.

Step 4: Attach the connector backto the ribbon cable - Place the end ofthe ribbon cable on the adhesive of theconnector back. The ribbon should fitperfectly into the scalloped dents in theconnector back - one dent per conduc-tor. Orient the parts exactly as shown,noting the location of the stripe on thecable, and that the cable end shouldbe flush with the side of the connectorback.

Step 5: Mate the connector parts- Being careful to orient the parts asshown here and in prior photos, pushthe connector back evenly into the con-nector front. It should stay in place.The conductor barbs need to line upwith each conductor in the ribbon.

Step 6: Press the connector partstogether - Using a vice (ideally),squeeze the connector parts togetheruntil you hear two tabs in the connec-tor snap into place. If your vice jawsare rough (knurled) or you are usingpliers or vice-grips, protect the connec-tor from the vice jaws with a stiff flatmaterial like plastic, wood, cardboard,brass shim-stock, etc.

11.6. MAKING LIMIT SWITCH CONNECTORS 147

Step 7: Fold the ribbon back - Ifyou are going to use a strain relief, foldthe ribbon cable back over the finishedconnector.

Step 8: Add the strain relief - Ifyou are using a strain relief, snap itinto the connector back with the cablefolded over underneath it as shown. Itshould snap into place on both sides ofthe connector.

11.6 Making Limit Switch Connectors

To simplify the installation and maintainability of the limit switches, the Model 1design calls for connectorized cables for the limit switches. Here you will see howto make this type of connector. If you happen to have a crimp pin/socket crimpingtool, then lucky you - you will not need these instructions. Otherwise, you will besoldering and crimping to obtain very robust connectors.


Step 1: Gather the parts -Gather the 2 conductor cable, the limitswitches, the crimp pins/sockets , andthe connector bodies. Referring to theassembly instructions for your model,cut the 2-conductor cable into piecesof the appropriate length. Strip thesheath and conductor insulation, andtin the stripped copper on both endsof the cable (see Stripping Cable andWire and Tinning Stripped Conduc-tors).

Step 2: Secure the crimppins/sockets - To simplify thesoldering process, secure the crimppins/sockets with tape to a block ofwood.


Step 3: Flux the conductors -Apply a small amount of flux to thestripped/tinned conductors on one endof the cable.

Step 4: Position in pin/socket- Position the fluxed conductor endsinto the back end of the pins/socketsas shown. The conductor should notgo more than 1/2 of the way intothe pin/socket. Ideally, (unlike in thephoto) the insulation should extendpast the tall flanges of the pin, andthe stripped conductor should extendpast the short flanges to roughly 1/2the length of the pin/socket. The tallflanges are designed to be crimped ontothe insulation, the short onto the con-ductor.


Step 5: Solder conductor - Withthe tip of your soldering iron, press theconductor down against the pin/socketfor about 3 seconds, and apply a smallamount of solder wire. You should seethe solder flow smoothly over the con-ductor and the pin/socket. Do not ap-ply too much solder, as it will clog thefront half of the pin/socket, which mustremain clear to connect to the limitswitch (see inset).

Step 6: Detach pins/sockets fromstrip - Once your soldering is done,break or cut the pins/sockets you havesoldered to off of the strip of crimps.


Step 7: Crimp pin/socket flanges- Using your needlenose pliers, fold thetwo sets of flanges of the pin/socketdown onto the soldered area. Fold firstone side down, then fold the other sidedown on top of the first. Do not bendthe front end of the pin/socket, as itsshape is important for connection tothe limit switch.

Step 8: Insert pins/sockets intoconnector body - Noting closely theshape of the connector and pin/socket,push the pins/sockets into the back ofthe connector body. They should snapinto place. You may need to use yourneedlenose pliers or a very small hexkey to push the pin/socket fully intothe connector body. Test your con-nector by pulling gently on the leads.The pins/sockets should stay inside ofthe connector body, and the conductorsshould stay inside of the pins/sockets.If you are not satisfied, fix the prob-lem now to save yourself greater trou-ble later.

Step 9: Connect to limit switch -The connector should now simply snapinto the limit switch

Step 10: Label your cable - Us-ing a labelmaker or masking tape, la-bel your cables by axis and directionaccording to the cable length specifica-tions from the assembly instructions forthe Fab@Home model you are building.


11.7 Using Protective Braiding for Cables

Polyester braiding provides abrasion protection for cables that will be moving, and aconvenient way to bundle cables together.

Step 1:Braid cutting and fraying -According to the assembly instructionsfor your Fab@Home model, cut lengthsof braid for you cables and bundles.Note that the end of the braid will frayquite quickly after being cut.

Step 2: Melt cut end of braid -Using a small flame, heat the cut end ofthe braid to partially melt it to preventit from fraying. Do not let it catch fire(unlike the photo).

Step 3: Wrap cable ends - To makethreading cables through the braid eas-ier, wrap some tape over the strippedends. Tape bundles of cable together tokeep them together during threading.

Step 4: Threading cable - The braidexpands in diameter when you push onit, allowing you to push a bundle of ca-bles through it. Simply push the cablesin one end and inchworm the braid overthe cable bundle until the bundle endcomes out of the other end of the braid.

11.8. GENERAL SOLDERING/DESOLDERING METHODS 153

Step 5: Secure with Ziptie - Use aziptie/cable tie to secure the braid tothe cable.

Step 6: Finished Cable - Here youcan see a motor with a cable extensionand protective braid.

11.8 General Soldering/Desoldering Methods

Molten solder is hot, and solder may contain lead. Please use eye protection and goodventilation (a fan or fume extractor) when soldering. Below you can find some moregeneral advice on soldering.

• General Soldering Technique(http://www.swarthmore.edu/NatSci/echeeve1/Ref/Solder/Soldering.html) atSwarthmore College.

• Makezine Video Tutorial(http://www.makezine.com/blog/archive/2007/01/soldering.tutor.1.html?CMP=OTC-0D6B48984890) A great video tutorial on soldering and desoldering

11.9 Soldering Technique

Source:

http://www.swarthmore.edu/NatSci/echeeve1/Ref/Solder/Soldering.html

11.9.1 Introduction

This section is a brief introduction to proper soldering technique. Solder is pronounced“sodder”, the “l” is silent. Is is assumed that you will be soldering the componentsto a PC (printed circuit) board. The directions below will get you acquainted withsome construction techniques.

Soldering irons, wire, PC board holders and other supplies are in 310. The sol-dering irons are on timers so that they can’t accidentally be left on, but you shouldtry to remember to turn them off when you are done.


11.9.2 Installing a component.

To install a component on the PC board, first hold the board with the component sidefacing you. This is the side of the board with writing on it. Start with the smallestcomponents, usually the resistors. Bend the leads of the device (if necessary) so thatthey will fit through the hold in the board with the device laying flat against theboard. Now bend the leads on the solder side of the board so the device doesn’t fallout (see below). You can place several components at the same time.

After several components have been ”stuffed” (the technical term for puttingcomponents on a board), you can solder them. Before soldering anything make surethe sponge on the soldering stand is moist. You should frequently wipe the tip ofthe iron on the sponge to keep it clean.

To solder a component turn the board over so the solder side is up. There aresome clamps for holding boards in the lab. To solder a connection hold the tip ofthe soldering iron on one side of the lead and hold it for a second or two. When thelead and the trace are hot, apply solder to the side of the lead that is away from theiron. The solder shouldn’t touch the iron directly. This ensures that the connectionis hot enough to form a bond with the lead and with the copper trace.

The solder should flow around the connection, and leave a smooth transition fromthe trace to the lead, as shown. If you have a ball, or the solder has a clumpyappearance you may need to redo the connection. If you need to remove solder wehave ”solder-suckers” and ”solder-wick”.

Good Solder Joint Bad Solder Joint

11.9. SOLDERING TECHNIQUE 155

Repeat this procedure with all components until you are finished.Other references about soldering that you may find useful:Soldering faq (http://www.epemag.com/solderfaq/default.htm) from “Everyday

Practical Electronics” (http://www.epemag.com). Includes some good photographs(http://www.epemag.com/solderfaq/pictures.htm) and techniques for desoldering(http://www.epemag.com/solderfaq/desold.htm).

Soldering primer (http://et.nmsu.edu/ etti/fall97/electronics/solder.html) fromNew Mexico State University.


Chapter 12

Model 1 Base Assembly

Here you will find the detailed instructions for assembly of the machine base (the boxholding all of the other parts) for the Fab@Home Model 1

157

158 CHAPTER 12. MODEL 1 BASE ASSEMBLY

159

Step 1 Materials Step 1 Materials (cont’d)

Step 1 Assembly - Close-up Step 1 Assembly Results


161

Step 2 Materials

Please see Step 4 below for a trick forinserting the bearings

Step 2 Materials (cont’d)

Step 2 Assembly - Close-up


163

Step 3 Materials Step 3 Materials (cont’d)

Step 3 Assembly Results Step 3 Assembly - Close-up


165

Step 4 Materials Step 4 Mid-Assembly

The bearings can be difficult to pressin. Using a rubber mallet may help(or in a poor college student’s case, aneraser and a hammer). A few light tapsshould do the trick.

Step 4 Assembly Results


167

Step 5 Materials Step 5 Mid-Assembly

Step 5 Assembly Results - Again, the method outlined in step 4 may be useful forinserting the bearing.


169

Step 6 Materials - Minus the ”BaseRear Panel” from step 2

It is easier to make sure the threadedinserts are properly inserted if you tryto screw into the holes before hangingon the large panel.

Step 6 Assembly - Don’t forget totighten on the pulley.

Step 6 Assembly Results


171

NOTE: BE VERY CAREFUL WHEN WORKING WITH THE ”BASE TOPPANEL”!! IT IS FRAGILE, AND CAN BREAK EASILY, ESPECIALLY AS YOUTRY TO INSERT IT INTO THE BACK PANEL!! (personal experience - Pkiddy)

After two casualties, success!


173


175


177


Chapter 13

Model 1 XY-Carriage Assembly

Here you will find complete instructions for assembling the XY-Carriage for theFab@Home Model 1.

13.1 Parts Needed for Building XY Carriage

In order to help speed up the build process, here is a list of the parts you will need toconstruct the XY carriage assembly. I was able to build this portion of the Fab@homein roughly 2 hours Pkiddy. Please update this number if it proves incorrect. I’m goingto work on getting pictures of the hardware up as I get time.

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180 CHAPTER 13. MODEL 1 XY-CARRIAGE ASSEMBLY

Part Photo Part Description QuantityNeeded

<no photo> 2-56 x 5/8” Screw 4<no photo> 2-56 Hex Nut 4<no photo> 4-40 x 1/2” Screw 4<no photo> 4-40 Hex Nut 4<no photo> M3 x 10mm Screw 4<no photo> 6-32 Brass Threaded Insert 24<no photo> 6-32 Square Nut 14<no photo> 6-32 Hex Locknut 6<no photo> 6-32 x 1/2” Screw 18<no photo> 6-32 x 5/8” Screw 20<no photo> 6-32 x 3/4” Screw 4<no photo> Wave Spring 7<no photo> Shaft Collar 3/16” Bore 1<no photo> Omron Limit Switch 2<no photo> Tapped Steel Linear Rail 2<no photo> Untapped Steel Linear Rail 2<no photo> Self-locking Threaded Insert 4<no photo> Pillow Block 4<no photo> Linear Ball Bearing 4<no photo> Ball Bearing 1<no photo> HSI External Nut for X,Y motors 4<no photo> HSI Linear Stepper Y - 12.878” Long Shaft 1

13.2. ASSEMBLY INSTRUCTIONS FOR XY CARRIAGE 181

Part Photo Part Description QuantityNeeded

Left XY Coupling Plate 1

Right XY Coupling Plate 1

XY Coupling Plate Nut Flange Brace 4

XY Coupling Plate Nut Flange 2

Tool Mount Spacer 1

Y Carriage - Top 1

Y Carriage - Side 2

13.2 Assembly Instructions for XY Carriage

Assembly Tips:Threaded Inserts for Thermoplastics




Step 2 Materials - Please ignore theacrylic piece on the bottom. I didthings a little out of order, becauseI didn’t have a heat gun or hairdryer readily available. Ultimately, theacrylic was a non-issue.

Step 2 Materials - A better look at thering that needs to be removed. It comesas part of the pill block.

I used a special tool to get the ring outof the block, although a pair of sharpneedle-nosed pliers will do the trick.

A better look at the ring.


Use the heat gun/hair dryer to warmup the block. After roughly a minute ofheating, the block will have expandedenough that the bearing should dropright in (a little push may be needed,but it should not be difficult). If atfirst it doesn’t seem to fit, just continueheating.

A look at the bearing inside the block.The heat gun had no affect on theacrylic.

The four blocks, complete with bearings inserted. Again, you do not need to havethe acrylic pieces attached to complete this step.





Step 4 Materials

Step 4 Mid-Assembly - No screws yet

Step 4 Assembly - Don’t tighten the screws down all the way yet. You’ll need someplay in the two acrylic pieces for step 5.



Step 5 Materials

Step 5 Mid-Assembly - No screws inyet. Apparently, I forgot to take apicture of the completed assembly, butyou can see it in the step 6 pictures.



Step 6 Materials - Also, a good look ata completed part from Step 5.

Step 6 Materials - Another look, tomake up for the picture lacking fromStep 5.

Step 6 Assembly Assembly Close-up



Step 7 Materials Step 7 Assembly



Step 8 Materials Step 8 Assembly



Step 9 Materials Step 9 Materials - cont’d

Step 9 Assembly - Both completedparts, mirrors of each other.

The one on the left is from the first timethrough steps 4-7, while the one on theright is the second time through, usingthe base part from step 8.



Step 10 Materials Step 10 Materials - cont’d

Step 10 Assembly



Step 11 Assembly



Step 12 Materials

Step 12

Step 12 Assembly



Step 13 MaterialsStep 13 Mid-Assembly - Half of the in-serts have been pushed into the acrylic

Step 13 Assembly

Assembly (cont’d)




Step 15 Assembly front Step 15 Assembly back



Step 16 Assembly top Step 16 Assembly front



Step 17 Assembly



Step 18 partial assembly

Tip: Put the side screw with its hex nutin first, and then slide the acrylic pieceinto place (you will need to move thescrew and nut around a little so thatthe acrylic can slide on.

Step 18 assembly

Step 18 full assembly



Step 19 materials

Tip: first put the screws into the nutand slide the wave washers onto thescrews

Line up the screws with the appropriateholes on the Y-carriage

Y-Carriage view

Do the same for the other side Step 19 assembly



Step 20 materials Screw motor into place

Thread motor shaft through Y-Carriage

Attach shaft collar at the end



Step 21 materials Step 21



Step 22 materials Step 22 assembly

Chapter 14

Model 1 Z-Carriage Assembly

Here you will find assembly instructions for the Z-axis carriage and build surface(table) for the Fab@Home Model 1.

14.1 Parts Needed for Building Z Carriage

In order to help speed up the build process, here is a list of the parts you will need toconstruct the Z carriage assembly. I was able to build this portion of the Fab@homein roughly 2 hours Pkiddy. Please update this number if it proves incorrect.

Part Photo Part Description Quantity Needed<no photo> 8-32 Brass Threaded Insert 13<no photo> 8-32 x 1” Screw 8<no photo> 8-32 x 3/4” 5<no photo> 6-32 Brass Threaded Insert 3<no photo> 6-32 Square Nut 16<no photo> 6-32 Hex Nut 4<no photo> 6-32 x 5/8” Screw 20<no photo> 6-32 x 1” Screw 3<no photo> Compression Spring 5<no photo> HSI External Nut for Z motor 1

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226 CHAPTER 14. MODEL 1 Z-CARRIAGE ASSEMBLY

Part Photo Part Description Quantity Needed

Z Carriage Chassis Bottom Acrylic 1

Z Carriage Chassis Front Acrylic 1

Z Carriage Chassis Middle Acrylic 2

Z Carriage Chassis Top Acrylic 1

Z Carriage Support Cross 1

Z Carriage Inner Table Support Truss 2

Z Carriage Outer Table Support Truss 2

Z Table 1

14.2 Assembly Instructions for Z Carriage

Assembly Tips for Installing Threaded Inserts into Plastic

14.2. ASSEMBLY INSTRUCTIONS FOR Z CARRIAGE 227


















A look at the springs installed underthe printing surface. I apologize, I for-got to take a picture of the materialsfor this step beforehand.

The springs can be difficult to wrestle into place. I found it easiest to put one on(screw through spring into threaded insert), but only enough that the screw catches.The spring provides enough leeway that the other springs can be held in place while ascrew is threaded through. If I get a chance, I’ll post details/pictures of my techniquePkiddy 15:12, 15 November 2006 (EST)



Chapter 15


Here you can find information about how to build a 1-Syringe Tool, and attach it toyour Model 1.


The Model 1 1-Syringe Tool is the standard deposition tool for the Fab@HomeModel 1. It uses disposable syringe barrels, tips, and pistons to hold the materials,and it uses the linear stepper motor method of controlling syringe piston position,hence material flow. This is the recommended tool for beginner fabbers, in that itallows the use of a very wide variety of materials, the materials do not need carefulpreparation, it operates in an intuitive fashion, and allows simple swapping of materialsyringes to build objects with multiple materials.

Because the syringe barrels, tips, and pistons are in direct contact with materials,we recommend using disposable components. The 1-Syringe Tool has been designed

247

248 CHAPTER 15. MODEL 1 1-SYRINGE TOOL

specifically for 10cc barrels from EFD Inc. The same type of components can befound from a variety of vendors, but we have not tested the compatibility of partsfrom other sources. If you find other compatible dispensing components, please addthem to the Syringe Tool Dispensing Components page.

15.1 Bill of Materials

Currently, the off-the-shelf structural parts for the syringe tool are included in theModel 1 bill of materials.

Disposable syringe barrels, pistons, and tips recommended for use with the 1-Syringe Tool are listed later in this chapter.

15.2 Acrylic Parts

Below you can find files in several CAD formats which describe the acrylic parts. Eacharchive should contain part files and an Excel spreadsheet which describes quantitiesof each part, recommended material, and recommended orientation for parts duringthe cutting process - the orientation affects the ease of assembly because many cuttingprocesses leave slightly tapered cuts.

Archives described as “Nominal Dimensions” show the parts with the exact di-mensions they should have once you have them in hand. Archives described as “Offsetby . . . for . . . ” have had the dimensions altered to compensate for effect of materialremoved by a cutting process so that the parts will end up with nominal dimensionswhen cut with the specified process.

Notes to Solidworks users:

1. SolidWorks Parts files REQUIRE INCH UNITS; parts contain equations whichare unit dependent

2. The primary part configuration (with long descriptive name) represents the partwith nominal dimensions.

3. Configuration named “Cut Compensated” is automatically offset to compensatefor tool kerf according to the global variable “Cut Compensation Offset” (see“Equations”)

4. “Cut Compensation Offset” is the one-sided offset of the part boundaries; e.g.should be set equal to 1/2 of the total width of cut associated with your process.

5. To generate drawings offset for your machining process, activate the “Cut Com-pensated” configuration, and adjust the “Cut Compensation Offset” variable.

6. Please cut parts with recommended part view facing (up) toward laser; kerfflare used to assist assembly


For Solidworks

• Fab@Home 1-Syringe Tool Acrylic Parts, .zip (5MB) of directory containingSolidWorks parts files at nominal dimensions and Excel instructions file, Evan18:21, 17 October 2006 (EDT).

• Solidworks Drawing Files

Other File Formats

• STEP

• DWG

• DXF

• Parasolid

• IGES

15.2.1 Offset by 0.0035” for 85W Laser Cutter (Koba Indus-

tries)

For Solidworks

• Fab@Home 1-Syringe Tool Acrylic Parts, .zip (23MB) of directory containingSolidWorks parts files offset by 0.0035” and Excel instructions file, Evan 18:21,17 October 2006 (EDT).

15.2.2 Layout DXF file

Offset by 0.0000” (nominal size) for Waterjet cutting

This Zip file contains a DXF layout in inches for one syringe holder using a 6”×12”piece of acrylic .

Layout DXF


15.3 Solidworks Assembly Files

Here is the Solidworks Assembly for the 1 Syringe Tool. I can try to save it as otherformats, but I’m not sure how well they’d translate. This one is roughly 6.8 MB.Pkiddy 13:41, 19 February 2007 (EST)

15.4 Part Images

Koba Industries of Albuquerque, NM has delivered a pilot run of parts for the syringetool. We are nearly ready to outsource the laser-cutting of parts!

15.5. MODEL 1 1-SYRINGE TOOL ASSEMBLY DIAGRAMS 251

15.5 Model 1 1-Syringe Tool Assembly Diagrams

Assembly Step 1



Assembly Step 2



Assembly Step 3



Assembly Step 4


15.6. MOUNTING THE 1-SYRINGE TOOL TO THE MODEL 1 CHASSIS 259

15.6 Mounting the 1-Syringe Tool to the Model 1

Chassis

Assembly Step 5 - Mounting 1-Syringe Tool on Model 1 Chassis


15.7. SYRINGE TOOL DISPENSING COMPONENTS 261

15.7 Syringe Tool Dispensing Components

In order to use your Fab@Home Model 1 with a Model 1 1-Syringe Tool, you willneed to obtain some disposable syringes, pistons, and needles/nozzles. The followingparts are the recommended starter set for use with the Model 1 1-Syringe Tool:


15.7.1 Parts list with pricing, vendor, part number

Part Qty Qty/ Total VendorPart DetailsReqd Pkg Price Num.

SyringeBarrel

30 30 $20.22 EFDInc.

5111LL-B 10cc clearpolyethy-lene syringebarrel; luertip

SyringePiston;Neo-prene;10cc

30 30 $15.54 EFDInc.

5111S-B Black neo-prene rubberpistons foruse with10cc syringebarrels

SyringeTipSam-plerKit

1 1 $42.34 EFDInc.

5100 A kit with awide varietyof differenttips; tip caps;end caps;some otherpiston types

15.7.2 Preferred vendors

Name URL/Contact Category DetailEFDIncor-po-rated

http://www.efd-inc.com/components.html,1(800)556-3484, 1(404)434-1680

Fluid Dis-pensingEquip-ment andSupplies

Syringe barrels,pistons, nozzlesand needles; com-plete dispensingsystems

15.8 Materials

This section lists a number of materials that can be used with a Model 1 1-SyringeTool, and similar deposition tools. If you discover or develop new materials, pleaseadd them to this page under the appropriate category. Please remember to describe:

• A material file to go with your material

• A recipe for making the material or a place from which to buy it (on the web)

• Some pictures of objects printed with that material

• Suggestions as to which syringe tips and other dispensing components to usewith the material

15.8. MATERIALS 263

• Post-processing for this material (e.g. curing, sanding)

• Material properties (elasticity, conductivity), if you know any

Warning: While some materials like silicone and playdough may be be-nign, other materials may be hazardous, toxic, carcinogenic, or flammable.Please carefully consider the following before using any inedible materials:

• Some materials, such as epoxy, release heat as they cure and can spontaneouslycombust if mixed in too large of a batch.

• Always follow safety and handling instructions that are provided with any ma-terial.

• Always download and read the Materials Safety Data Sheet for any new ma-terial, or any material you might be using in an unusual way. Check themanufacturer’s or vendor’s websites or reference sites, such as MSDS Online(http://www.msdsonline.com) for MSDS’s for materials you plan to use.

• Be sure to use appropriate personal protective equipment when working withhazardous materials, including eye, face, hand, body and respiratory protectionas needed. See a reference site, such as:http://www.pp.okstate.edu/ehs/links/ppe.htm for advice on protective equip-ment.

• Be sure to dispose of material carefully and in accordance with EPA regulations(http://www.epa.gov/epaoswer/osw/resident.htm)(in the USA), or the wastedisposal regulations in your country.

15.8.1 Structural Materials

• Gypsum

• Plaster

• Playdough

• HotGlue

• Putty

• Polymer Clay?

• Metal Particle Clay?

• Uv Coating? you can use it with the syringe tool, and then apply the uv light,or you can spread it as a layer apply the uv light and then cut the layer to theshape is needed.


• Casting materials such as fast-setting epoxies or rubber? Machinable wax? (e.g.freemansupply.com or shapelock.com)

• ABS plastic in solution? I saw on a crafts page somewhere that you can dissolveABS in acetone and use it to patch up defects. With the right amount ofdilution, you might be able to deposit it with a syringe and wait for the acetoneto evaporate. Probably need a fume hood/recapture system, though.

• Wax? I would like to build a system with a heated wax reservoir to make partsthat could then be used to cast plastic or metal parts.

15.8.2 Elastomers

• Silicone

• Rubber Cement

15.8.3 Conductive inks

• Conductive paste

• CircuitWriter Conductive Ink

• Solder It-Silver Bearing Solder Paste

15.8.4 Metals

TODO: Low melting point alloys (require heated tool) Should mildly toxic materialsbe considered? E.g., those alloys containing Pb.

• Gallium alloys - maybe an alloy of Ga, In, Sn?

• Field’s Metal

• Solder

15.8.5 Edible

• Easy Squeeze Frosting

• Icing

• Peanut Butter

• Cookie Dough

• Chocolate

• Caramel

15.8. MATERIALS 265

Materials: GypsumDescription: Soft ceramicRecipe/Source:

• http://plaster.com/DryStone.html

• http://plaster.com/SuperX.html

Materials: PlaydoughDescription: Playdough, Clay, ModelMagic (Various Colors)Recipe/Source: http://www.crayolastore.com/category.asp?NAV=CLAYProperties:

• ModelMagic: Very elastic material, which means the material must be com-pressed a lot in order to be pushed out of the syringe tip; very light, supportsitself well

• Crayola’s Air-Dry Clay: Consider adding water to soften clay

Materials: HotGlueDescription: Hot glueRecipe/Source: Adhesive Tech Standard Glue Sticks (Walmart ˜$2)Properties: quite tough and cheap materialRecommended tools: A deposition tool has to be built from a glue gun: the heater

can be adapted, with a thin nozzle, and a piston will push the glue stick. As the glueis extruding into thin wires, even when pressure is released, a mechanical device maybe needed to stop the flow. The nozzle may be designed to squeeze the depositedglue, like in Stratasys old FDM machines

Safety and Toxicity: No problem, as far as I know.Materials: Silicone

Description: 1-part elastic Silicone (White/Black/Clear)Recipe/Source: http://www.newark.com/product-details/text/catalog/7481.htmlMaterial File:NAME PDMS Standard Home Silicone

DESCRIPTION Silicone polymer (PDMS), white

RECIPE Standard, get from GE Model GE5000 12C

COLOR 1 1 1 1 // R G B Alpha in range 0-1 (alpha=transparency)

VISCOSITY 65000 cP

COMPRESSIBILITY 0.8

ELASTICITY 12 KPa

LAYERWAIT 0 sec

CURING 10 min

COMPATIBILITY Silicone, fluoropolymer, polyolefin

INCOMPATIBILITY acetone

NOZZLEMIN 0.5 mm

NOZZLEMAX 10 mm

PREFERREDTOOL 10ccPinkTaper.tool


PREFERREDTOOL 10ccRedTaper.tool

FENCING 0 mm

MAXOVERHANG 45 deg

EARLYSTART 0.5 sec

EARLYSTOP 0.5 sec

Newark: one-part silicone systems

2.8 oz. Tube

10.1 oz. Tube

One and two component rubber adhesives for an unlimited number of industrialapplications. Packaged in collapsible plastic tubes and standard caulking cartridges.Cures to tough resilient rubber at room temperature. Will withstand temperaturesfrom -70F to 500F. Resists moisture aging, ozone weathering. Will bond to mostsubstrates without primer. Ideal for instant insulation. Available in 2.8 oz tube or10.1 oz caulker as indicated below.

GENERAL-PURPOSE PASTE, UL, FDA AND NSF LISTEDMfg. Part No. Description Newark

Part No.IS 802-2.8 Oz. White General-Purpose Paste 00Z1574IS 802-10.1 Oz. White General-Purpose Paste 00Z1577IS 803-10.1 Oz. Black General-Purpose Paste 00Z1578IS 808-2.8 Oz. Clear General-Purpose Paste 00Z1576IS 808-10.1 Oz. Clear General-Purpose Paste 00Z1579

15.8. MATERIALS 267

PREMIUM PERFORMANCE PASTEProduct available in either 2.8 oz tube, 10.3 oz tube or 10.1 oz caulker as indicated

below.Mfg. Part No. Description Newark

Part No.RTV 102-2.8 Oz.** White Premium Paste 00Z643RTV 102-10.1 Oz.** White Premium Paste 00Z659RTV 102-10.3 Oz.** White Premium Paste 00Z652RTV 103-2.8 Oz.** Black Premium Paste 00Z644RTV 103-10.1 Oz.** Black Premium Paste 34C2573RTV 106-2.8 Oz.** Red High Temperature Paste 00Z646RTV 106-10.1 Oz.** Red High Temperature Paste 00Z1134RTV 106-10.3 Oz.** Red High Temperature Paste 00Z655RTV 108-2.8 Oz.** Clear Premium Paste 00Z645RTV 108-10.3 Oz.** Clear Premium Paste 00Z654RTV 108-10.1 Oz.** Clear Premium Paste 00Z660RTV 133-2.8 Oz.** Black Flame Retardant Paste, 00Z1316

Noncorrosive(UL-94V-0 Rating)RTV 157-2.8 Oz. Grey Ultra High Strength Paste 00Z649RTV 159-2.8 Oz. Red Ultra High Strength and 00Z650

High Temperature PasteRTV 167-2.8 Oz. Gray Electronic Grade 03C3308

FLOWABLE SILICONES, UL, FDA, NSF LISTED Product is available in 2.8 oztube and 10.3 oz tube as indicated below.

Mfg. Part No. Description NewarkPart No.

RTV 112-2.8 Oz. White Premium Grade, Flowable 00Z648RTV 112-10.3 Oz. White Premium Grade, Flowable 00Z656RTV 116-10.3 Oz. Red High Temperature Grade, 00Z657

FlowableRTV 118-2.8 Oz. Clear Premium Grade, Flowable 00Z647RTV 118-10.3 Oz. Clear Premium Grade, Flowable 00Z658

LOW-ODOR NEUTRAL CURE ADHESIVES, UL LISTED Product is available in2.8 oz tube and 10.1 oz caulker as indicated below.


RTV 122-10.1 Oz. White General-Purpose Paste 00Z1571RTV 128-10.1 Oz. Clear General-Purpose Paste 0Z1573RTV 160-10.1 Oz. White Electronic Grade, Noncorrosive, 00Z1313

FlowableRTV 162-2.8 Oz. White Electronic Grade, Noncorrosive Paste 00Z651RTV 162-10.1 Oz. White Electronic Grade, Noncorrosive Paste 00Z662RTV 123-10.1 Oz. Black General-Purpose Paste 00Z1572RTV 6708-10.1 Oz. Clear Paste 00Z1264


TWO-PART RTV KITS 1 pint kit silicone rubber compound for protectingconnectors switches, components and coils from dust, moisture and shock, and

casting rubber release rolls.Mfg. Part No. Description Newark

Part No.RTV-11 White Silicone Rubber Compound 00Z735RTV-60 Red Silicone Rubber Compound 00Z1050

1 pint kit rubber compound for electronic potting for optical clarity. Protectselectronic components against shock, moisture and other environmental hazards.


RTV-615 Clear Silicone Rubber Compound 00Z716

c©2007 NewarkWeb Site Support:1.800.NEWARK.T (1.800.639.2758) Contact Newark:1.800.4.NEWARK (1.800.463.9275)Materials: Conductive paste

Description: Silver filled epoxy. Low resistance, brittle.Recipe/Source: E1660 conductive ink by Ercon Inc.

http://www.erconinc.com/home.htmMaterials: CircuitWriter Conductive Ink

Description:Recipe/Source: CircuitWriter

CAIG Laboratories, Inc: CircuitWriterTM

CircuitWriterTM

Conductive Ink, silver-basedTECHNICAL INFORMATION:Color: SilverBinder: AcrylicSolids content by weight: 51.5%Density: 14.1 lbs/galElectrical Resistance: < 0.017 ohm/sq/milShielding Performance: 76 dBViscosity: 20-25 sec., #2 Zahn Cup

@ 25 oCIdeal Film Thickness: Between 0.4 and 1.0 milsTheoretical Coverage: 340 Sq ft/gal @ 1 milVOC Content: 0.50 lbs/gal

TYPICAL PROPERTIES WHENDRIED:Sheet resistance: 0.017ohms/sq/mil (25 µm)Attenuation: 76 dB

CircuitWriterTM

Precision Conductive Ink

15.8. MATERIALS 269

Apply instant traces on most surfaces (epoxy, glass, plastic, metal).Draw traces on circuit boards, repair defective traces, make jumpers and shield elec-tronics, design prototype circuits and repair rear-window heater traces.

CircuitWriterTM Pen, #CW100PCircuitWriterTM Pen, 100%, silver-based, 5 gramsPart No. CW100P Price: $16.95

CircuitWriterTM , #CW100L-4 CircuitWriterTM Liquid, 100%, silver-based, 125 grams, coated bottlePart No. CW100L-4 Price: $116.95

CircuitWriterTM , #CW100L-12 CircuitWriterTM Liquid, 100%,silver-based, 375 grams, containerPart No. CW100L-12 Price: $325.00

CircuitWriterTM , #CW100L-32 CircuitWriterTM Liquid, 100%,silver-based, 1000 grams, containerPart No. CW100L-32 Price: $875.00


Materials: Solder It-Silver Bearing Solder Paste

Description: Solder It: Silver Bearing Solder Paste

SolderIt Package

Recipe/Source: Lowe’s - $3.97

Recommended tools: Used to solder electrical wires together. It is a metallic-colored paste until heated with flame of match. Unfortunately, the paste - prior toheating - is not conductive while it is still wet. More details to follow as testingcontinues.

Field’s metal


Field’s metal, or Field’s alloy, is a fusible alloy that becomes liquid at approx-imately 62 C (144 F). It is a eutectic alloy of bismuth, indium, and tin, with thefollowing percentages by weight: 32.5% Bi, 51% In, 16.5% Sn.

As it contains no lead nor cadmium, it is a non-toxic alternative to Wood’s metal.

It is used for die casting and easy prototyping.

Materials: Icing

Description:

Recipe/Source:

• http://www.crayolastore.com/product list.asp?SKW=CRACAKE

• Supermarket

Properties:

• Crayola’s Writing Icing: Not as thick as other icings; flows well; takes about 1hour to begin hardening, several hours to completely harden; washes away wellwith hot water (possible support materials?)

Materials: ChocolatePreliminary Experiments with Chocolate

The following is the work of Noy Schaal, a freshman in Manual High School,Louisville, KY. Noy is building a low-temperature heated syringe which is suitablefor depositing chocolate. This modification to the basic Model 1 1-Syringe Tooloffers the ability to deposit other low-melting point materials as well, including wax,bismuth metal alloys.

Photos from 01/20/2007

15.8. MATERIALS 271

High Resolution - smaller size: can fitto your palm or your finger tip

Photos and Movies from 12/03/2006

Getting rid of the air


5.2MB Movie of Printing a ChocolateBar

15.8. MATERIALS 273

2.1MB Movie of Printing a Chocolate Bar

7.2MB Movie of Printing a Chocolate Bar

40.6 MB Movie of Printing a Chocolate Bar



Melting the Chocolate

Black Chocolate

15.8. MATERIALS 275

White chocolate



15.8. MATERIALS 277


Chapter 16


The Model 1 2-Syringe Tool is a simple modification to the 1-Syringe tool, just wider,with 2 motors, and two syringes. At present only the SolidWorks design files are avail-able. The assembly is essentially identical to that of the 1-Syringe tool. PLEASENOTE: The 2-Syringe Tool has an additional motor which will require an additionalmotor amplifier, and the addition of a couple of cable connections between the mi-crocontroller and the additional amplifier.

Video of 2-Syringe Tool system in ac-tion 53MB WMV.

Image of the electronics for a 2-SyringeTool system - note the addition of asingle axis Xylotex amp to the usual4-axis amp of the standard Model 1.

16.1 Software

Here you can find the current version of the application (same exe as for a standardModel 1) packaged with a printer definition and tool files for 2-syringe system.

Beta Version

Link: Fab@Home V0.20 Application with 2-Syringe printer and tool files, FAHv0 18.zip

Version: 0.20

Date: 03:08, 15 May 2007 (EDT)

Platform: Windows 2000/XP/2003

Format: Zip archive

279


Size: 407KBRequires: Firmware Version 3

16.2 Designs

Link: 2-Syringe Tool SolidWorks Design Files, 2SyringeTool.zipVersion: 1.0Date: 17:03, 17 January 2007 (EST)Platform: SolidWorks 2005 SP3.1Format: Zip archive of SolidWorks filesSize: 3.6MBOther File Formats: DXF, layout file only

Chapter 17

Model 1 Chassis Assembly

Here you will find the assembly instructions for the Model 1 Chassis. If you arelooking for CAD files of the chassis for cutting your own, or places that will cut thechassis parts for you, please visit the Fab@Home:Model 1 Bill of Materials Page.

Image of Fully Assembled Model 1 Chassis

The Model 1 Chassis consists of:

281

282 CHAPTER 17. MODEL 1 CHASSIS ASSEMBLY

Image of Model 1 base - Base AssemblyInstructions

Image of Model 1 Z-Carriage - Z-Carriage Assembly Instructions

Image of Model 1 XY-Carriage - XY-Carriage Assembly Instructions

17.1. MODEL 1 CHASSIS ASSEMBLY DIAGRAMS 283

17.1 Model 1 Chassis Assembly Diagrams








Chapter 18

Model 1 Electronics Assembly

The Model 1 Electronics consist of:

• Elpac MW4024-760-NC-WH 24VDC, 1.67A (40W) Power Supply

– Elpac Datasheet

• AC Power Cord (IEC 3 prong to USA 3 prong plug) for Power Supply

• Olimex LPC-H2148 Microcontroller Board

– Olimex LPC-H2148 Header Pinouts

– Olimex LPC-H2148 Schematic

– Philips LPC-214x ARM7 Family User Manual

• Xylotex XS-3525/8S-4 4-Axis Stepper Motor Amplifier Board

– Xylotex Datasheet

• Winford Engineering DB-25 Breakout Board

– Winford Datasheet

• Omron D3M-01K3 SPST-NC (Single-pole Single-throw Normally Closed) LimitSwitches

– Omron Datasheet

• Limit Switch Cables

• Ribbon Cables to connect the LPC-H2148 to the other devices

• USB Cable to connect LPC-H2148 to the user’s personal computer

291

292 CHAPTER 18. MODEL 1 ELECTRONICS ASSEMBLY

18.1 Constructing the Model 1 Electronics

The following steps are required to assemble the electronics for the Model 1:

1. Prepare the motor cables

2. Prepare the limit switch cables

3. Prepare the ribbon cables

4. Prepare the amplifier enable cable

5. Prepare the power supply cable

6. Route the cables

7. Modify the Xylotex Board for the Limit Switches

8. Attach the Enable Cable to the Winford Board

9. Mount the boards onto the chassis

10. Connect the cables to the boards according to the schematic and the electronicspinouts

18.2 Modify Xylotex Board for Limit Switches

Schematic of the resistor network circuit for the 10pin SIP resistor network

The Xylotex XS-3525/8S-4 4-Axis Stepper Motor Amplifier Board is nicely de-signed with a set of screw terminals to allow simple connection of devices to anyauxiliary input/output signals coming onto the board via the IDC26 connector. Wewill use these terminals to connect our limit switches, and the limit switch signals willthen travel to the LPC-H2148 via the IDC26 to DB25 cable, through the Winfordboard, and then over the IDC26 cables to the microcontroller. In order for the limit

18.2. MODIFY XYLOTEX BOARD FOR LIMIT SWITCHES 293

switches to provide a signal, they need to change the voltage on the Xylotex aux IOpins when the switch is activated - this is generally achieved by placing the switchin a series circuit with a resistor, and monitoring the voltage between the resistorand the switch. There are two configurations for this circuit - Vcc->switch->resistor->ground (”pulldown”), and Vcc->resistor->switch->ground (”pullup”). Pullup isgenerally preferred for safety, as the resistor between Vcc and the other componentslimits current in the case of a short. In ether case, when the switch state changes(opened or closed), the voltage between the switch and resistor changes from Vccto GND or vice-versa. The Xylotex board does not have these pullup or pulldownresistors onboard, however it does have a nice spot for a 10pin SIP (single inline pack-age) resistor network - 10 tinned holes just behind the black aux IO screw terminalblock. Because of the on-board connections to these holes, we have opted to use the”pullup” circuit configuration, and you will need to run a wire from a Vcc (5VDC)screw terminal to the screw terminal at which pin 1 of the SIP is connected (see theschematic below). Here you will see how to solder the 10pin SIP network onto theboard.

Step 1: Here you see the Xylotexboard and the 10 pin SIP resistor net-work, and the destination for the SIPhighlighted

Step 2: The SIP has been insertedinto the tinned holes prior to solder-ing. Note the orientation of the ”Pin1” marking.

Step 3: Bend the first and last lead ofthe SIP slightly to keep it from fallingout during soldering.

Step 4: Apply a small amount of fluxto each of the leads of the SIP


Step 5: Heating the lead and thetinned hole simultaneously, add a smallamount of solder until the hole fills, anda small amount of solder climbs up thelead (see Soldering Methods for generalsoldering advice)

Step 6: Clean off any excess flux, andexamine your work - the solder shouldbe neat and smooth around all of theleads of the SIP. If you spot any ballsof solder or holes which do not appearfilled, resolder that lead now, to saveyourself debugging hassles later.

18.3 Attach the Enable Cable to the Winford Board

Note that amplifier enables require firmware version 3.

In this step, you will solder the amplifier enable cable that you made earlier tothe Winford breakout board.

Step 1:Flux the stripped and twistedend of the enable cable, and solder it inone of the plated through-holes (PTH)labeled ’X1’ on the Winford board.The four PTH’s for each terminal areall connected to the screw terminal ofthe same name. ’X1’ and ’X2’ are theonly terminals which do not connectto the DB-25 ribbon cable connector.

Step 2:Your attached enable cableshould look like this.

18.4. MOUNTING THE BOARDS 295

18.4 Mounting the Boards

The diagrams below illustrate how to mount the boards onto the back of the Model1 base.


18.4. MOUNTING THE BOARDS 297


18.5. ELECTRONICS PICTO-SCHEMATIC 299

18.5 Electronics Picto-Schematic

This schematic illustrates the connections between the various electronics boards andother components of the Fab@Home Model 1.

Schematic of the electronics layout, revised 5-4-07 - added amplifier enableconnections

18.5.1 Visio Schematic

Current Version

• Link: Model 1 Electronics-05042007.vsd

• Version: 5-4-2007

• Date: 14:16, 4 May 2007 (EDT)


• Platform: Windows 2000/XP/2003

• Format: Microsoft Visio XP/2003

• Size: 300kB

Previous Version

• Link: Model 1 Electronics.vsd

• Version: 3-28-2007

• Date: 13:36, 28 March 2007 (EDT)


• Format: Microsoft Visio XP/2003

• Size: 300kB

18.5.2 Cable Attachment Images

Following the schematic and/or thepinouts, attach the ribbon cable con-nectors to the LPC-2148, and then at-tach the tinned ends of the ribbon ca-bles to the Winford board screw termi-nals.

Here’s how the ribbon cables look whenattached to the LPC-H2148 and theWinford board.

18.5. ELECTRONICS PICTO-SCHEMATIC 301

Plug the enable cable jumper ends intothe ENABLE (J?) header (white, be-tween TB-AUX and J7). Leave the pinclosest to TB-AUX unconnected.

Here is a closeup of the limit switchconnections. Note that for each limitswitch, one of the wires will be con-nected to the ground terminal at thebottom of the Xylotex board. Depend-ing on the gauge of your limit switchcables, this bundle may not fit into thescrew terminal. For this reason, it isrecommended that you ”pigtail” theselimit switch conductors together - sol-der them all together, and then solderthat bundle to a short piece of wire.Shrink tube the solder joint. This ar-rangement will make a more reliableconnection to the screw terminal forthe limit switches.

Here’s a view of all of the cables con-nected, and the electronics mounted onthe back of the machine.


18.6 Electronics Pinouts

Full electronics pinout and pin assignment information: The below Excel workbookincludes several sheets that describe the pin assigments and cable connections for thevarious electronic components. Please use this as a complement to the Schematicsand the User Manuals and Board Schematics


• Link: Model 1 Pinouts-05042007.xls

• Version: 05042007

• Date: 14:16, 4 May 2007 (EDT)

• Platform: Microsoft Excel

• Format: Microsoft Excel XP/2003

• Size: 296kB

Chapter 19

Model 1 Firmware Installation

The firmware is the software that runs on the LPC2148 microcontroller.When you receive your microcontroller, it will have a simple demonstration firmware

loaded onto it from the manufacturer. You will need to replace this with the Fab@Homefirmware. There are several ways to put the firmware onto your microcontroller, allof which will require that you buy a programming adapter. The simplest method isto buy a JTAG cable for ARM processors (20 pin, 2 rows X 10 pins). Most ARMJTAG cables will work with CrossWorks so this is the recommended approach. Seebelow for a list of recommended JTAG adapters.

An alternative method involves using the serial bootloader on the LPC-H2148with a precompiled hex file, Philips serial programming software, and a serial/TTLUART adapter connecting your PC to the first UART on the LPC-H2148. I’ll try toget more into this soon, as it is probably the cheapest approach.

19.1 Firmware Object Code Downloads


• Link: Fab@Home Firmware V3 ELF file, FAHv3ELF.zip

• Version: 3

• Date: 00:39, 10 May 2007 (EDT)


• Format: Zip archive

• Size: 16KB

19.1.2 Legacy Versions

• Link: Fab@Home Firmware V2 ELF file, FAHv2ELF.zip

• Version: 2

303

304 CHAPTER 19. MODEL 1 FIRMWARE INSTALLATION

• Date: 00:39, 10 May 2007 (EDT)



• Size: 14KB

19.2 Programming your LPC-H2148 with Rowley

Crossworks v1.6

1. Download the Rowley CrossWorks Chip Support Package for the NXP (formerlyPhilips) LPC2000 family

2. Run CrossWorks version 1.6

3. In the “Tools” menu, select “Install Package. . . ”, and navigate to theNXP LPC2000.hzq file you downloaded above. This provides Crossworks withsome chip-specific details which are necessary to communicate via JTAG withthe LPC-H2148.

4. Download and unzip a firmware object file

5. Connect your JTAG and USB cables as in the instructions below.

6. Hit CTRL-ALT-T to bring up the Targets window (or “Target->Targets”)

7. In the Target window, right click the Macraigor Wiggler 20 Pin (or the typeof JTAG you are using), and select Connect.

8. Right click Macraigor Wiggler 20 Pin again, and select “Erase All” whichwill erase the flash memory of your micro. You should be asked TWICE toconfirm via dialog boxes. If you do not see a second dialog saying “All erasablememory will be erased. Are you sure you want to continue?”, then the JTAGmay not be communicating properly - but try the remaining steps anyway.Please contact Evan for assistance.

9. If erasing succeeds, then right click Macraigor Wiggler 20 Pin again, andselect Download File->Elf File

10. Navigate to the firmware .elf file you downloaded above.

11. CrossWorks should download the binary to the microcontroller flash memory.

12. You’ll know if it worked, because after a few seconds, the green LED on themicro should start flashing with a 2s period, and Windows should try to installthe drivers for Fab@Home or USB->Serial adapter.

19.3. FIRMWARE DEVELOPMENT ENVIRONMENT 305

13. You can test operation of the firmware by running the Fab@Home application,initializing the hardware, and checking the ”Firmware version” number at thetop of the “View->Printer Status” window.

19.3 Firmware Development Environment

The firmware has been written in C using Rowley CrossWorks for ARM(http://www.rowley.co.uk/arm/index.htm) which is available for a 30 day free trial -more than enough time to program your micro, and possibly to play with the firmwareas well. NOTE: If you want to use Rowley CrossWorks for free, you needto request an evaluation license - this generally takes about 24 hours whenyou make your request via email. CrossWorks simplifies the installation of theFab@Home firmware onto the microcontroller, hence it is recommended that youdownload the trial and use it for programming.

19.3.1 Download Rowley CrossWorks for ARM

Rowley CrossWorks for ARM Free 30 day Trial, MS Windows:http://www.rowley.co.uk/arm/arm crossworks 1 6 win.zip.

19.3.2 Download Chip Support Package for the LPC2000Family

Rowley CrossWorks Chip Support Package for the NXP (formerly Philips) LPC2000family: http://www.rowleydownload.co.uk/arm/packages/NXP LPC2000.hzq.

19.3.3 Install CrossWorks and Request Evaluation License

Step 1: Once you have downloaded theCrossWorks installer package, unzip it,and open the arm crossworks. . . \ armfolder, and double click Setup.exe.You can accept all of the defaults re-garding installation destinations.

Step 2: Start CrossWorks for ARM.With CrossWorks running, you needto request an evaluation license. GotoTools-> Licence Manager. . .


Step 3: On the License Manager di-alog box, click one of the two buttonsin the upper right hand corner underthe text “If you wish to evaluate Cross-Works...”. If you use an email appli-cation, like Eudora or Outlook, click“By Mail”, which will open your emailprogram and address an email to Row-ley Co. with a license key request. Ifyou use a web-based email client, click“Manually”, and see Step 4.

Step 4: If you chose “Manually”, a di-alog will appear notifying you that a li-cense key has been copied to the Win-dows Clipboard. You can then com-pose an email to [email protected] the subject “Evaluation LicenseRequest”, paste in the license key, andsend it. You should receive a 30 dayevaluation license within 24 hours (onweekdays).

Step 5: Once Rowley has respondedwith an “Activation Key”, you canenter it into the CrossWorks Li-cense Manager. Select “Tools->LicenseManager...”, click “Activate Product”,paste in your activation key, and ok it.You should see your license type de-scribed in the License Manager dialognow.

Step 6: In the “Tools” menu, se-lect “Install Package...”, and navigateto and open the Philips LPC2000.hzqchip support package you downloadedabove. This provides Crossworks withsome chip-specific details which arenecessary to communicate via JTAGwith the LPC-H2148.

As an alternative, there is a variety of GNU C compiler-based toolsets which canwork with the ARM7 core. For more info on these see:

• Olimex’s ARM-USB-OCD Page: http://www.olimex.com/dev/index.html

• SparkFun’s ARM-USB-OCD Page:http://www.sparkfun.com/commerce/product info.php?products id=7834.

19.4. PROGRAMMING YOUR LPC-H2148 MICROCONTROLLER 307

19.4 Programming your LPC-H2148 Microcontroller

Programming the microcontroller with CrossWorks involves connecting it to yourPC via a JTAG adapter and the USB cable (simultaneously), running CrossWorks,opening up the Fab@Home Firmware project, telling CrossWorks to connect to themicrocontroller via the JTAG cable, and building and running the ARM Flash Releaseversion of the firmware. This last command will download the firmware object codeonto the flash memory of the microcontroller, and then reset the microcontroller.After that, you should be ready to run the application.


Step 1: Download and unzip theFab@Home firmware project, which in-cludes C and assembly language sourcecode, a memory map for the LPC-2148,some runtime glue object code, and aRowley CrossWorks project file (.hzp).

Step 2: Start up CrossWorks.

Step 3: Using “File->Open Solu-tion...” or CTRL-SHIFT-o, bringup the Open Solution dialog,and navigate to and open [email protected] projectfile located in the FAHFirmware folderyou unzipped in step 1.

Step 4: Using the second drop-down control from the top left of theCrossWorks window, select the cur-rent project configuration to be ARMFlash Release. This is telling Cross-Works that you would like to com-pile the “release version” of the projectwithout extra code which makes debug-ging easier, but decreases performance,and that you want it to be stored on theflash memory of the LPC-2148 so thatit does not disappear when the micro-controller is not powered.

19.4. PROGRAMMING YOUR LPC-H2148 MICROCONTROLLER 309

Step 5: Get out your JTAG adaptercable. Pictured here is the ARM JTAG20 pin to Parallel Port adapter fromSpark Fun, and a parallel extension(male to female) cable, which is op-tional, but extends the reach of theJTAG cable somewhat.

Step 6: If using the Parallel to JTAGadapter, connect it to the parallel portof your PC.

Step 7: Connect the 20pin female 2-row socket of your JTAG adapter tothe black 20pin male header on the topface of the LPC-H2148 microcontrollerboard. Note that the connector andsocket are ”keyed” with a tab and slotso that they can attach in only one ori-entation.

Step 8: Now connect your PC to theLPC-H2148 USB port with a USB ca-ble. This will provide power to the mi-crocontroller. You should see the redpower LED on the micro illuminate,and within a few seconds, you may ob-serve that the mouse pointer on yourPC screen is moving on its own in asquare pattern. This is a result of the”demonstration” firmware that comespreloaded on the microcontroller fromOlimex, the board’s manufacturer.


Step 9: Return the PC, and using the“Target” menu, select the connectionappropriate for your JTAG adapter - inthe case of the parallel to JTAG, select”Connect Macraigor Wiggler (20 Pin)”.This tells CrossWorks to try to talk tothe microcontroller over the JTAG ca-ble connection.

Step 10: If connection was successful,you should see a yellow target connec-tion indicator near the bottom of theCrossworks window. Yellow indicatesa successful but inactive connection. Ifyou have any errors at this stage, dou-ble check your cable connections andpossibly disconnect and reconnect, en-sure that the red power LED is lit onyour micro, and ensure that you havea valid license for CrossWorks. As par-allel ports are not reliably “plug andplay”, you may need to reboot your PCafter attaching the parallel port cablebefore things will work.

Step 11: Push and hold down the re-set button on the microcontroller. Thiswill stop the firmware on the microfrom running so that you can regaincontrol of your mouse for the last cou-ple of steps.

Step 12: While holding down themicrocontroller reset button, contortyourself toward your PC, and in theCrossStudio application, select ”Build->Build and Run”, and simultaneouslyrelease the microntroller reset button.

19.5. JTAG ADAPTERS 311

Step 13: The project should begincompiling and you should now see alarge number of warnings and othertext scroll in one of the lower panesof the CrossWorks window. The warn-ings are a result of duplicate registername definitions resulting from usingcombining code from multiple (open)sources.

Step 14: You should eventually seea successful build, and then noticesthat the memory of the micro is beingerased, and new firmware downloadedand verified.

Step 15: If all of this succeeds, thenyou should see three lit LED’s on yourmicrocontroller. The red Power LEDand Yellow USB Link LED shouldbe constantly lit, and the Green Sta-tus LED should be blinking, 1 secondon, 1 second off, indicating that thefirmware is running and detects no er-rors. Your microcontroller is now fullyprogrammed, and ready to communi-cate with the Fab@Home application.

Step 16: You can now disconnectthe JTAG cable from the microcon-troller, and start working with yourFab@Home!

19.5 JTAG Adapters

In order to program your LPC-H2148 you will need a JTAG adapter which workswith your firmware development environment.


19.5.1 JTAG for Rowley Crossworks

At present, the following two JTAG adapters are known to be compatible with RowleyCrossWorks:

• Parallel Port to ARM JTAG adapter from SparkFun, $19.95, if you have aparallel port

• USB to ARM JTAG adapter from Rowley, ˜$200, if you only have a USB port

19.5.2 JTAG for ARM GCC Toolchain

Olimex the manufacturer of the LPC-H2148 board, has a simplified set of program-ming tools for the ARM processors, called their “Olimex’s ARM GCC for WindowsDummies”, based on the GNU C ARM toolset. Olimex makes a very nice “all inone” JTAG adapter, called ARM-USB-OCD for use with these free programmingtools, but currently it is unknown whether this will work with Rowley CrossWorks aswell - if you know, please update this!

• JTAG USB OCD Programmer/Debugger for ARM processors from SparkFun,$69.95, works with RS232 serial and USB

19.6. ROWLEY CROSSWORKS FOR ARM 313

19.6 Rowley Crossworks for ARM


19.7 Olimex JTAG Programmer (from Sparkfun

Electronics)

JTAG USB OCD Programmer/Debugger for ARM processorsSparkfun Electronics SKU#: PGM-07834Price: $71.95

Description: This is the mother of all JTAG Programmers for ARMs - and it’sabout 1/10th the price of other programmer/debuggers with the same functionality!

• First on market three-in-one USB JTAG debugger - offers JTAG + RS232 (fullmodem signals supported) port + power supply all in one compact device

• Fast speed USB 2.0 JTAG dongle interface, can be used with all ARM devicesfor programming and debugging.

• Uses ARM’s standard 2x10 pin JTAG connector

• Supports ARM targets working in voltage range 2.0 - 5.0 V DC

• Software supported by OpenOCD (open source) debugger

• adds virtual RS232 port to your computer with all modem signals like: DTR,DSR, DCD, RTS, CTS, Rx, Tx

• Can be used as power supply to your target board with three jumper selectablepower supplies: 5V 9V and 12VDC, USB source current is limited with resetablefuse at 300mA, at the different output voltage the maximum current is different:5V/200mA, 9V/100mA, 12V/70mA, note that this also depend on your USBhost current capabilities, if other USB devices are attached to your computer orif the laptop is running on batteries these figures may be different and dependon your computer USB host.

• Comes with CD with Windows installer for full featured and open source toolsas alternative to the commercial ARM development packages: GCC C compiler,openOCD debugger and Eclipse IDE.

19.8. SPARKFUN ELECTRONICS: JTAG PROGRAMMER 315

Dimensions: 50x40 mm (2x1.6”) + 20 cm (8”) JTAG cable + 30 cm (12”) powersupply cable

Documents:

• ARM-USB-OCD flyer

• ARM Cross Development with Eclipse (10MB) REV-3 very detailed tutorialby Jim Lynch how to setup and works with the free GNUARM tools LPC2106board. The sample codes for this tutorial is here.

• ARM Cross Development with Eclipse in Spanish language (3MB) REV-1 PaulAguayo did a great job translating to Spanish language Jim Lynch’s tutorial. Healso shrink the size of the document without missing the quality of the picturesand tutorial text.

• GNU toolchain setup with openOCD by Michael Fischer

• ARM JTAG connector (top view)

Software:

• Olimex’s ARM GCC for Windows Dummies install CD - installs onyour computer WinARM + OpenOCD debugger + Eclipse for out of the boxdevelopment with the open source GNU C compiler and OpenOCD debugger,supports flash loading on LPC and external flash for LPC-H2214, LPC-H2294,with make examples for different ARM controllers.

• openOCD open source debugger from Dominic Rath for debugging with In-sight/GDB.

• WinARM - easy to install open source GCC toolchain by Martin Thomas. Weare working on CD install package for WinArm+OpenOCD+ARM-USB-OCDsupport

• For the moment the only supported package is GCC C compiler + openOCDdebugger + Eclipse IDE. Olimex can provide the necessary information andcooperate with interested parties if they want to add low cost USB debuggersupport to their C compilers and IDEs.

19.8 Sparkfun Electronics: JTAG Programmer

JTAG Programmer/Debugger for ARM processors

SKU#: PGM-00275

Price: $20.95


Description: JTAG Programmer and Debugger for LPC and ARM microcon-trollers.

• Program LPC21xx, Atmel AT91, STMicroelectronics STR7 Parts, and other(not tested) ARM flash microcontrollers

• Uses ARM’s standard 2x10 pin JTAG connector

• No external power supply required - all power is taken from the target board

• Compatible with Rowley’s CrossConnect, IAR EWARM and GCC (OCD) soft-ware for programming, real time emulation, debugging, step by step programexecution, breakpoints, memory dump etc. Everything a high priced emulatorcan do and more!

• IAR EWARM - unlimited assembler code size or in C with 16K limit for allLPC21xx ARM microcontrollers

• Works with free GCC C compiler and Insight tool chain and debugger.

Documents: ARM-JTAG.pdf, ARM JTAG ConnectorDimensions: 2x1.6” (50x40 mm) + 8” (20 cm) cableSoftware: Please take a look at our support forum for further discussions on

software compatibility and support for the ARM-JTAG.In general, LPC21xx are very new parts. And for some unknown reason, Philips

doesn’t disclose how to program LPC21xx Flash via JTAG. This has delayed thedevelopment of third party IDEs. Perhaps Philips is having problems with the Flashprogramming and is going to change the protocol in future. This is currently whythey force end users to use their bootloader IAP protocol. The only vendor so farto work around this is Rowley. They first load in RAM small own bootloader whichthen receives data from the JTAG interface and feeds the packets into IAP to writeto Flash segments. This is current the easiest to use product for the LPC21xx parts.

• Jim Lynch’s tutorial for setting up the free GCC/GNU tool chain. The examplesoftware is available here.

• GCC C compiler from Macraigor Systems. Works smoothly with ARM-JTAGbut can’t program Flash and user can compile debug programs in RAM thenre-build for Flash and use Philips’ RS232 bootloader.

19.8. SPARKFUN ELECTRONICS: JTAG PROGRAMMER 317

• GNUARM another GCC toolchain from Arius.

• CrossWork for ARM (so far most recommended by us) C compiler and debugerfrom Rowley Associates, this is the easiest to use package we have tested, workssmoothly with ARM-JTAG and programs both Flash and RAM on LPC21xx

• EWARM C compiler and debugger (free for assembly language, 16K limit forC) from IAR Systems. Can’t program LPC21xx Flash, user can debug andprogram only in RAM, then re-build project and use Philips’ ISP utility toload the program through RS232 bootloader. C-SPY driver for ARM-JTAGhave some glitches on newer and faster computers and does several crashesbefore connect to target. It works fine on older and slower computers though.According to IAR, they are going to fix this to the end of February 2004.

• SwiftX software development system for the ARM family works with the ARM-JTAG for live interactive debugging of the Atmel AT91 ARM core family (usingAtmel’s EB40, EB40A, etc. development boards). Port for the ST ARM partscoming soon.


Chapter 20

Model 1 User Software Installation

Here you can find the most up-to-date Fab@Home software executables (applicationand USB drivers) for the Model 1 with installation instructions. Currently, thissoftware runs only under Microsoft Windows.

If you are interested in participating in the development of the open-source Fab@Homeapplication, firmware, or drivers, please visit the Fab@Home project at:http://sourceforge.net/projects/fabathome.There is a narrated overview movie of the Fab@Home application at:http://fabathome/org/wiki/uploads/7/79/SoftwareOverview.wmv.

20.1 Application Download


• More work necessary before we can declare an official release Evan 11:33, 5December 2006 (EST)

20.1.2 Beta Version

• Link: Fab@Home V0.20 Application, FAHv0 20.zip

• Version: 0.20

• Date: 03:05, 15 May 2007 (EDT)



• Size: 396KB

• Requires: Firmware Version 3

319

320 CHAPTER 20. MODEL 1 USER SOFTWARE INSTALLATION

20.1.3 Legacy Version

• Link: Fab@Home V0.17a Application, FAHv0 17a.zip

• Version: 0.17a

• Date: 14:45, 3 December 2006 (EST)



• Size: 407KB

• Requires: Firmware Version 2

20.2 Drivers Download


Unavailable

20.2.2 Beta Version

• Link: Fab@Home USB driver V1.0, FAHDRVv1 0.zip

• Version: 1.0

• Date: 11:09, 6 September 2006 (EDT)



• Size: 34KB

20.2.3 Legacy Version

Unavailable

20.3 Installation instructions

1. Download the Fab@Home Application and Drivers .zip archives:

2. Unzip the archives to your desktop or another convenient location using WinZipor another .zip decompression utility. The resulting folders should look roughlylike the images below:

20.3. INSTALLATION INSTRUCTIONS 321

Application archive, unzipped

Drivers archive, unzipped

1. When you plug in the USB cable from your Fab@Home to your PC, Windowswill request the drivers for the Fab@Home unit. Just navigate to the FAHDRVfolder, and select the driver file requested. You will need to do this up toFOUR times when you first connect to the Fab@Home. After this, the driverswill automatically load whenever the Fab@Home is connected.

2. You can verify that the drivers are installed by opening the Windows DeviceManager, and examining the Ports (COM & LPT) and Universal SerialBus controllers lists. You should see TWO USB to Serial Port Adapters withCOM port numbers (e.g. COM17 and COM18 in the image), and at least oneUSB Composite Device controller.

322 CHAPTER 20. MODEL 1 USER SOFTWARE INSTALLATION

Device Manager showing loaded drivers

Chapter 21

Model 1 Commissioning

Here you will see how to adjust and prepare your Model 1 fabber for use after finishingassembly.

21.1 Mount the belt

Here you will see how to mount the timing belt which joins the motorized and unmo-torized sides of the X axis gantry. The belt ensures that the two sides of the X axisare driven at the same speed so that the X and Y axes remain perpendicular to eachother at all times. You will mount the belt over the pulleys, adjust and secure therelative position of the left and right sides of the X axis so that the X and Y axes areperpendicular, and then adjust the tension of the timing belt with the belt tensioner.

Step 1: Position the machine with therear facing you, and have the timingbelt and your Allen wrenches handy.

Step 2: Ensure that the right-hand (Xmotor side) timing pulley is positionedas shown, with the wave-spring washercompressed between the pulley and thebearing, and that the pulley hub is se-curely tightened. Turn the pulley backand forth by a single turn - it shouldturn smoothly, and you should see theXY Carriage move slightly as well.

323

324 CHAPTER 21. MODEL 1 COMMISSIONING

Step 3: Slightly loosen the two #8screws which secure the belt tensioneruntil you can slide the belt tensionerup and down. Also loosen the left-handtiming pulley so that it will slide easilyoff of the shaft.

Step 4: Lay the timing belt aroundthe right-hand pully and belt tensionerpulley.

Step 5: Slide the left-hand timing pul-ley off of its shaft, being careful to leavethe spring washers on the shaft. Loopthe timing belt around the pulley, andslide it back onto the shaft.

Step 6: By turning the motor shaftsby hand, maneuver the XY Carriage sothat the Y Carriage is at the left/rightcenter, and very near to the rear of themachine (closest to you).

21.2. TRUING THE XY CARRIAGE 325

Step 7: Without rotating the belt orany of the pulleys, and without, turnjust the left-hand X shaft until the backof the Y Carriage (for instance, the rearsurface of the bearing pillow blocks) areparallel to the nearest edge of the topof the Machine Base.

Step 8: Carefully tighten the lefthand timing pulley without rotatingthe shaft or the belt, remembering tosqueeze the pulley against the bearingto preload the wave spring washer.

Step 9: Now reposition the shaft collarat the front of the left-hand X shaft toensure that the left-hand X shaft doesnot have any axial play. Loosen theshaft collar, pull the shaft toward thefront of the machine, squeeze the shaftcollar against the bearing (recompress-ing the wave spring washer between thepulley and the bearing at the rear ofthe machine), and retighten the shaftcollar.

Step 10: Slide the belt tensionerdownward until the belt can easily bedeflected only about 1/2” up or down- the belt should deflect upward toroughly the bottom edge of the jointbetween the rear and top surfaces ofthe machine base. Secure the belt ten-sioner screws to keep it at the correcttension. Too little tension will let thebelt slip over the pulleys, too much ten-sion will bend the X axis shafts andcause premature wear of parts.

21.2 Truing the XY Carriage

The X and Y axes’ components need to be adjusted so that the X-rails are parallel toeach other, the Y-rails are parallel to each other, and the X-rails are perpendicular to


the Y-rails. If this is not done, the carriages will not move freely, causing prematurewear, and stalling of the motors. Fortunately, the Model 1 is not very sensitive toalignment. Truing of the X rails can be achieved merely by loosening the the screwsthat secure the rail flange mounts to the machine base, moving the carriage back andforth to ensure free motion, and gradually tightening the screws while ensuring thatmotion remains free from end to end. The Y rails are similarly trued by moving theY carriage back and forth, but need a different set of screws tightened.

Step 1: With the rear of the machinefacing you, ensure that all of the #8screws which secure the X rail flangemounts to the machine base are loose.

Step 2: By pulling on the timing belt,drive the XY carriage all of the wayto the front of the machine then all ofthe way to the back, being careful tonot force the carriage against the limitswitches - just stop when you hear thelimit switches click.

Step 3: Now gently tighten the #8screws on the right front X rail flangemount.

Step 4: Repeat steps 2 and 3 for eachof the other 3 X rail flange mounts, be-ginning with the right rear. When youare done, you should be able to drivethe XY carriage smoothly from one endto the other of its range of motion withlittle force on the belt. If you notice achange in force at one end of the rangeof motion, repeat the above steps.

21.3. ADJUSTING MOTOR CURRENT 327

21.3 Adjusting motor current

The Xylotex stepper motor amplifier regulates the current through the stepper mo-tors. The current needs to be set for the HSI motors. If the current is set too high, themotors will overheat, while if too low, the motors will not generate sufficient torque,resulting in loss of position while following paths.

The recommended method for performing the adjustment is to adjust the 4 po-tentiometers (variable resistors) to achieve a desired voltage at the 4 testpoints onthe board. Use a multimeter (voltmeter) to measure the voltage at the 4 test pointsrelative to a ground point on the board.

The Xylotex User Manual provides the relationship between the voltage at thetestpoints and the motor current:

Motor Current = V/1.44

Model 1 Motor Current SettingsMotor Recommended Test Point Test Point

Current VoltageX Motor (HSI Size 14, 5V) 0.57 A TPX 0.8208 VY Motor (HSI Size 14, 5V) 0.57 A TPY 0.8208 VZ Motor (HSI Size 14, 5V) 0.57 A TPZ 0.8208 V

1-Syringe Tool Motor (HSI Size 11, 5V) 0.42 A TPA 0.6048 V


The Xylotex 4-Axis amplifier has test-points and potentiometers (adjustableresistors) that you can use to measureand adjust (respectively) the currentdelivered to each motor. When youreceive the board from the manufac-turer, the currents will typically be setmuch too low for the motors used in theModel 1.

To measure the current, set your multi-meter to read DC Volts, and groundyour meter to the negative (white)power supply terminal and probethe labeled test points on the board.Here you see the testpoint for the X-axis being probed.

21.4. LEVELING THE Z-TABLE 329

Use a Philips screwdriver to turn thepotentiometer (blue) to adjust the cur-rent.

For each axis, adjust the potentiome-ter until the voltage you read roughlymatches the value listed for that axisin the table above. Remember thatthe voltage you read from your multi-meter is not equal to the current de-livered to the motor - you need to di-vide the voltage value by 1.44 to calcu-late the current.

If you do not have a multimeter, you can probably adjust the current graduallyupward, perhaps 1/8 turn on the potentiometer at a time, while feeling the temper-ature of the motor cases with a bare finger. Give 5 minutes between adjustments forthe temperature to stabilize. When you find the motor is getting too hot to touchwith a bare finger, turn the current down by 1/8 turn.

21.4 Leveling the Z-Table

The Z-table is mounted to the Z-carriage atop springs. These springs allow the tableto be leveled relative to the plane of the XY-carriage. It is important to have theZ-table parallel to the XY plane so that the deposition tool maintains a constantdistance from the table during fabbing. The table leveling procedure is simple, iftedious, and consists of driving the tip of the syringe in the syringe tool over thesurface of the table, adjusting the table mount screws until the table is level relativeto the XY plane of the XY Carriage. With a syringe (with a tip attached) insertedin the 1-Syringe Tool, manually turn the motor shafts and belt to position the tip ofthe syringe at the left rear corner of the table, just touching the table.


Step 1: Insert a syringe with a nee-dle/nozzle attached into the 1-SyringeTool. To do this, manually turn the sy-ringe tool motor shaft until the tip ofthe shaft is almost flush to the motorbody. The top of the syringe should betipped toward the tool body, lifted ashigh as possible, then the tip can betilted toward the body, snapped intoplace, and slid downward until the bot-tom of the syringe barrel is resting onthe bottom plate of the tool body.

Step 2: By manually turning the Z-axis motor shaft with your hand, adjustthe height of the table until it touchesthe tip of the syringe.

21.4. LEVELING THE Z-TABLE 331

Step 3: By pulling on the X-axis beltand manually turning the Y-axis motorshaft, drive the tip of the syringe to thefour corners of the table, while observ-ing the clearance between the tip andthe table.

Step 4:Adjust the (five) table levelingscrews to change the height of the tablewhere necessary so that the tip clear-ance from the table remains constantas you move the tip around the fourcorners and center of the table.


Chapter 22

Using Model 1

22.1 Video Guides

• A Narrated Overview of the Fab@Home Application is available at:http://fabathome.org/wiki/uloads/7/79/SoftwareOverview.wmv.

22.2 Quick Start User Guide

22.2.1 Step 1: Make Connection

Step 1.1 Step 1.2

1.1 Simply plug the USB cable from an available USB port on your PC to theUSB connector on the LPC-H2148 microcontroller board on the back of your Model1.

1.2 You should see 3 LED’s light up on the LPC-H2148 board:

• the red LED indicates that the board has power from the USB port

• the yellow LED indicates that the USB bus is connected

• the flashing green LED indicates the status of the firmware running on themicrocontroller via the pattern of flashing; 1 second on, 1 second off indicateshealthy status

333

334 CHAPTER 22. USING MODEL 1

22.2.2 Step 2: Install Drivers

Step 2

2.1 If this is the first time you have connected your PC to the Fab@Home, youwill need to install the drivers.

22.2.3 Step 3: Run Application

Step 3.1

Step 3.2

Step 3.3

3.1 Start the Fab@Home application by double clicking the [email protected] iconin the application folder you downloaded.

3.2 If this is the first time you have run the Fab@Home application, you may seean “Unidentified Publisher Warning”

22.2. QUICK START USER GUIDE 335

3.3 If this is the first time you have run the application, or you have changedyour printer definition file, you will need to load a printer configuration file, using the“Printer->Load Configuration. . . ” menu item.

3.4 You should see a graphical display which resembles your Fab@Home Model 1.

22.2.4 Step 4: Initialize Hardware

Step 4.1 Step 4.2

4.1 Select the “Printer->Initialize Hardware” menu item to begin communicatingwith the Model 1

4.2 Verify communications by examining the Status display (accessed via CTRL+U,or “Printer->Show Status”); if connected, “Elapsed Time (ms)” should be increment-ing, and “COM Port Handle” should be a positive number.

4.3 If not communicating, see the Application Troubleshooting page.


22.2.5 Step 5: Power On

Step 5.2

5.1 Plug in the power cord of your Model 1 into any standard outlet. The powersupply is international (50-60Hz, 100-240VAC), and should work in any country pro-vided an appropriate power cord or plug adapter.

5.2 A red LED should light up on the Xylotex board to indicate that it is receivingpower.

22.2.6 Step 6: Verify Motion

Step 6

6.1 Bring up the Jog Tool (CTRL+T or “Printer->Jog Tool”) and Jog Carriage(CTRL+J or “Printer->Jog Carriage”) dialogs.


6.2 Using the up/down arrows at the right edges of the dialogs, test that all of theaxes are moving. You should see both the graphical display in the application andthe actual Model 1 axes moving in the same directions by the same amounts.

22.2.7 Step 7: Adjust Motor Current

Step 7

7.1 If this is the first time you have run your Model 1, you will need to adjustthe motor current to ensure that the motors do not overheat, but are getting enoughcurrent for good acceleration.

22.2.8 Step 8: Define Tool/Material

8.1 If you are using a material and/or syringe needle/tip combination that you havenot used before, you will need to define a new .tool settings file and add the tool tothe .printer printer configuration file.

The following info should get you started: When you are setting up your newmaterials, it’s good to start from a tool file for a material that is similar to the oneyou are working with. Save a copy with an appropriate descriptive name, then editthe file: Change the comment at the top Change the name and description fieldsto match your material and syringe tip You should then tune certain parameters sothat you get desirable results when building some small test part (e.g. a small thinrectangle).


The main parameters to tune are:

• PATHWIDTH

• PATHHEIGHT

• PUSHOUT

• SUCKBACK

• DEPOSITIONRATE

The PATHWIDTH and PATHHEIGHT (both in mm) tell the path planning al-gorithms the distance between the horizontal slices/layers of your model (PATH-HEIGHT) and the separation between the paths within a layer (PATHWIDTH).Start out by making these both roughly the internal diameter of your needle/tip. Forrunny materials, the PATHHEIGHT should be made smaller and the PATHWIDTHlarger based on your intuition.

DEPOSITIONRATE (a dimensionless ratio) determines the linear distance movedby the syringe tool plunger per linear distance (along a deposition path) moved by theX and Y axes – basically how much material to deposit per unit length of a tool path.A high DEPOSITIONRATE will try to push a large amount of material out along thepath, tending to make the deposited strand of material wider, taller, and typicallymessier. A small DEPOSITIONRATE will tend to push insufficient material fromthe syringe, and the strand of material will typically be broken, tend to adhere to thesyringe tip rather than the part or build surface. Try to adjust the DEPOSITION-RATE until the flow of material leaves the tip of the syringe at the same rate thatthe XY motors traverse along the path. Ideally, DEPOSITIONRATE should simplybe (Cross-section area of Syringe Needle)/(Cross-section area of Syringe Piston) =((Needle ID)/(Piston OD))ˆ2. It is recommended that you start by calculating thisvalue, then adjust it slightly as necessary.

PUSHOUT and SUCKBACK are both delays for the starting and stopping of thesyringe motor relative to the motion along a path. They are defined in seconds. Whenboth values are positive, the syringe motor will start driving the syringe plunger toextrude material PUSHOUT seconds before the XY motors begin to traverse the cur-rent path, and the syringe motor will transition to full reverse SUCKBACK secondsbefore the XY motors reach the end of their current path to stop the flow of materialfrom the syringe. The goal is to adjust both of these parameters so that your ma-terial deposition starts and stops precisely at the beginning and end of the desiredpath without pooling, dripping or stopping too soon.

Starting with version 17a of the Fab@Home application, you can update several ofthe tool parameters “online” - meaning while a build is underway. This enables you tostart building an object with your best guess for parameters, then tune some of themwhile the build is underway, so you can see the effect right away. To change parametersonline, simply edit the .tool file and save it, then in the Fab@Home Application, use“Tool”->”Refresh Parameters.” You should see a change on the very next path(after completion of the current path). The parameters that can be changed online


in this fashion are PUSHOUT, SUCKBACK, and DEPOSITIONRATE. Changes tothe PATHWIDTH and PATHHEIGHT parameters will not affect a build that isalready underway – they only affect the processing (path planning) steps, prior tothe commencement of fabrication.

22.2.9 Step 9:Load and Manipulate STL File(s)

Step 9.1Step 9.2

Step 9.3

9.1 Using the “Model->Import Geometry...” menu item, navigate to the .STL filewhich describes the geometry of the part you would like to build, and open the file.

9.2 The geometry should be displayed on the virtual build surface in the graphicaldisplay of the application.

9.3 The geometry can be translated, rotated, and resized as desired using the“Model->Translate”, “Model->Rotate”, and “Model->Scale” menu items, respec-tively. If these menu items are not available, try clicking once on the part geometryto select it.


22.2.10 Step 10: Assign Properties to Part Geometry

Step 10

10.1 Bring up the Chunk Properties dialog box by double clicking on the partgeometry, or by using the “Model->Properties...” menu item.

10.2 This dialog allows you to tell the Fab@Home system what material and toolsettings you would like to use to build the part geometry you have imported, and alsoto modify the color and transparency of the part geometry in the graphical display.

22.2.11 Step 11: Inserting/Removing Syringes and Chang-ing Materials

Step 11.2/11.6 Step 11.3/11.5


Step 11.4

11.0 Prepare your syringe barrels, pistons, and tips

11.1 At this point, you should load a syringe barrel with the material you are goingto use to build the particular part. See Material Handling Tips for some suggestionson how to do this.

11.2 Whether or not a syringe is currently in the tool, you need to retract the toolshaft to provide clearance to insert/remove a syringe. If a syringe is inserted, use thehandle on top of the tool motor shaft to unthread the shaft from the syringe piston.

11.3 Now either by manually turning the motor shaft, or by using the Printer->Jog Tool dialog box in the Fab@Home Application, retract the motor shaft untilthe lower shaft end is clear of the syringe barrel and near the bottom of the motorbody.

11.4 To remove a syringe, slide it straight upward until the top of the syringe hitsthe underside of the plate on which the motor body is mounted. Tilt the tip of thesyringe out toward you, and unsnap the syringe barrel from the upper restraint.

11.5 Insert the new syringe by snapping the upper part of the barrel into the upperrestraint of the tool body, then sliding the syringe as high as possible, then tilt thetip away from you into the tool body, and slide the syringe downward until seated allof the way down into the tip restraint.

11.6 Insert the motor shaft by manually turning it or by using the Jog Tool dialogbox until the lower tip of the shaft is in contact with the syringe piston.

11.7 Manually turn the motor shaft until the tip of the shaft threads into the nutinside of the syringe piston.


22.2.12 Step 12: Cover Build Surface

12.1 Many materials will adhere to the build surface, so it is recommended that youcover the build surface with a thin disposable or washable material, such as aluminumfoil, plastic wrap, etc. We recommend Glad Press-N-Seal plastic wrap, as it is slightlystretchy, but adheres to the Z-table, so that you can stretch all of the wrinkles outand secure it without using adhesive tape.

22.2.13 Step 13: Set Positions

Step 13.1 Step 13.2

Step 13.3

For safe operation, and to ensure that graphics and the physical system are coor-dinated, the system needs to have 3 positions identified by you:

13.1 The Home Position

• The Home Position defines the orgin of the coordinate system used by theFab@Home. When facing the front of the Model 1, the home position is withthe build surface at its lowest point, against its bottom limit switch, and with thetool head at the left rearmost position, against the left and rear limit switches.

13.2 The Build Origin


• The Build Origin defines the starting point for deposition of material - yourpart will be built starting at this location. The build origin is up to you,but it is recommended that you try the center of the build surface (roughly(x,y,z)=(100,100,120)), then carefully adjust the z-height until the syringe tipjust touches the build surface.

13.3 The Safe Position

• The Safe Position provides a safe and convenient place for the carriage to moveto when paused, e.g. to change material syringes, to wipe the syringe tip clean,and to prevent accidental dripping of material onto the part being built. Thesafe position is also up to you, but it is recommended that the build surfaceheight at the safe position be lower than at the build origin, and that thetool be brought to the front of the Model 1 for convenient access (roughly(x,y,z)=(200,200,50)).

13.4 Bring up the Jog Carriage dialog box, and use it to drive your Model 1carriage to each of the locations in turn. At the appropriate location, click the “SetHome”, “Set Origin”, or “Set Safe” button to save the coordinates of the location.

22.2.14 Step 14: Plan Process

Step 14.1 Step 14.214.1 Use the “Fabrication->Plan Process” menu item to generate toolpaths for

the part you are building.

14.2 You can use the “View” menu to examine the paths without the shadedmodel rendering. Use the mouse wheel and the mouse to zoom in and rotate theview, respectively.

22.2.15 Step 15: Verify Material Flow / Flush and Wipe theNozzle

15.1 Bring up the Jog Carriage and Jog Tool dialog boxes. Using the Jog Carriagedialog, go to the safe position by hitting the “Go to Safe” button.


15.2 Once at the Safe position, use the Jog Tool dialog to feed some material outof the syringe by advancing the motor position VERY GRADUALLY, until you seea small amount of material emerge from the tip.

15.3 Using the Jog Tool dialog box, reverse the motor position slightly to stop thematerial flow.

15.4 Wipe the tip of the syringe clean.

22.2.16 Step 16: Execute Process

16.1 Use the “Fabrication->Start Printing” menu item to commence the fabricationprocess.

16.2 Follow any requests made by the software during the process, including chang-ing materials.

16.3 If at any time you need to interrupt the process momentarily, e.g. to replacea nearly empty syringe, or to wipe the tip, use the “Fabrication->Pause Printing”menu item. Pausing will cause the Model 1 to move to the Safe Position.

16.4 To resume after a pause, use the “Fabrication->Resume Printing” menu item,and the system should resume building where it left off prior to the pause.

22.2.17 Step 17: Power Off

17.1 Once the part is completed, be sure to send the Model 1 back to the HomePosition using the Jog Carriage dialog, and unplug the power supply.

22.3 Troubleshooting

22.3.1 Application runs, but hardware is not responsive at

all

Open the “Printer->Show Status” or “View->Show Printer Status” dialog. If the”Firmware Elapsed Time (ms)” value is not changing, then the application is no longercommunicating with the microcontroller. Use “Printer->Shutdown Hardware”, thendisconnect the USB cable from the Model 1, then reconnect, wait for 10 seconds (forthe drivers to reload) and hit “Printer->Initialize Hardware” and check the “ShowStatus” dialog again. If the problem persists, disconnect the USB cable, and rebootyour PC, then reconnect and restart the Fab@Home application

• Application runs, hardware is initialized, but axes will not move

Power off your machine, and move the motors by hand so that none of the limitswitches are being hit. Now power it back on. With your hardware initialized, openup the “Printer->Show Status” dialog. The LIMIT SWITCHES should all read “1,”indicating that they are not being hit. Try hitting each one and make sure it changesto a zero. If any of them are not switching on and off correctly, then you might havea wiring fault/short in the switches. If the microcontroller thinks a limit switch isbeing hit, it prevents the axes from moving.

22.4. MATERIALS TIPS 345

22.3.2 Software stops working

Reset the Driver

When the application is repeatedly restarted, sometimes the software will stop work-ing and the driver on the printer must be reset.

1. Click Printer > Show Status. “Elapsed time” is no longer incrementing

2. Shutdown Hardware: Printer > Shutdown Hardware, or close Fab@Home Ap-plication.

3. On the printer, near the printer cable connection, there is a restart button.Press the button once and wait 5 seconds before restarting software.

4. Initialize Hardware: Printer > Initialize Hardware, or open Fab@Home Appli-cation.

22.3.3 Other questions

For other questions, please view our Support Center.

22.4 Materials Tips

22.4.1 Loading a Syringe

One key to successfully using the fabber is making sure that there are no air bubblesin the syringe. With air mixed in with the building material, the flow from the nozzletip is not uniform, and results in poor dispensing. Some methods for avoiding airbubbles are outlined below.

Materials from Tubes

In the case of materials that come in tubes, like silicone, the easiest way to avoid airbubbles is to load the material through the tip. With the plunger inserted fully, thematerial can be pushed in from the tube, and will force the plunger backward as thesyringe fills. As you can see in the rightmost picture below, sometimes a little extraforce is needed to load the syringe this way.


Getting Out Air Bubbles

If the above method will not work, you can slide a wire down alongside the plunger.As the plunger is depressed, the air can escape through the gap provided by the wire.

22.5 Design Tools

CAD and geometric modeling programs allow you to define geometry using a varietyof tools. Once you have designed your 3-dimensional model, export it as an STLfile. This format is used to describe object geometries. If the part contains multiplematerials, save the geometry of each part as a separate STL file, then reassemblethem in the Fab@Home application.

22.5. DESIGN TOOLS 347

22.5.1 Free CAD Programs

• Blender (http://www.blender.org/) a full-featured open source 3D modeller thatsupports importing and exporting in many formats (including STL)

• Autodesk Inventor/LT (http://labs.autodesk.com/technologies/inventor.lt) Pre-view available for download only in the United States and Canada.

• BRL-CAD (http://www.brlcad.org/) A powerful Constructive Solid Geometry(CSG) solid modeling system with over 20 years development and productionuse by the U.S. military. Windows, Linux, MAC, BSD, and IRIX distributionsas well as full source code available. (follow link to Project Site / Download)

• Alibre Design Xpress. Commercial CAD, 30-day trial:(http://www.alibre.com/xpress/software/alibre-design-xpress.asp)

• DesignCAD (http://www.upperspace.com/) Commercial CAD, not free (30 daytrial).

• FreeCAD (http://www.askoh.com/) FreeWare closed source CAD. Free versiondoes not import dxf/dwg.

• Art of Illusion (http://www.artofillusion.org/) free, open source 3D modellingand rendering studio, written entirely in Java.

• CAELinux (http://www.caelinux.com/), a Linux LiveDVD (PCLinuxOS) loadedwith engineering open-source software, including CAD and analysis. Default3D CAD packages include BRL-CAD, Blender, qCAD, Paraview, and Graphi-teOne. Can be run from DVD (without touching Windows PC) or installed tothe computer.

• DAVID Laserscanner (http://www.cs.tu-bs.de/rob/david.html), a 3d scannerthat works using a webcam and a laser pointer

• 3d object converter (http://web.axelero.hu/karpo/) Shareware (30 day trial)convert many 3d file formats. Unregistered version does not export into stl.

• Google SketchUp (http://sketchup.google.com/)

– Sketchup to STL plugin (http://fabathome.org/wiki/uploads/d/d3/Su2stl.rb)- Save this plugin in the Google Sketchup/Plugins folder. Seems to havetrouble with curves, though I am still experimenting. Pkiddy 20:25, 13October 2006 (EDT)

• MoI3d (http://moi3d.com/)

• MeshLab (http://meshlab.sourceforge.net/) an open source tool for editing/check-ing/cleaning/simplifying/hole-filling large unstructed meshes.


• CB Model Pro (http://cbmodelpro.com/) A “pro” version of Cosmic Blobs(http://www.cosmicblobs.com/) (see below). The beta version is being offeredfor free (for a limited time).

22.5.2 Commercial CAD Programs

• SolidWorks (http://www.solidworks.com/)

• Autodesk Inventor (http://www.autodesk.com/inventor)

• 3ds Max (http://www.autodesk.com/)

• AutoCAD (http://www.autodesk.com/autocad)

• AliasStudio (http://www.autodesk.com/)

• Rhinoceros (http://www.rhino3d.com/)

• Pro/E (http://www.parametrics.com/)

• formZ (http://www.formz.com/)

• Cosmic Blobs (http://www.cosmicblobs.com/) – 3D art “for kids” – but it’s aserious package from SolidWorks. It can generate STL files. See CB Model Pro.

• Mudbox (http://www.mudbox3d.com/index.html) “Brush-based” high end 3Dsculpting software.

A comprehensive list of CAD Companies is at:(http://en.wikipedia.org/wiki/List.of.CAD.companies).

22.5.3 Misc Programs

The following programs can be used to view the STL files outside of the Fab@Homeprogram.

• SolidView Lite (http://www.solidview.com/svlite.html)

SolidWorks has several free programs that allow you to view its files without thefull version of SolidWorks.

• eDrawings (http://www.solidworks.com/pages/products/edrawings/eDrawings.html)

– eDrawings can view both SolidWorks files and AutoCAD files.

• SolidWorks Viewer (http://www.solidworks.com/pages/products/solutions/viewer.html)

– SolidWorks Viewer can read SolidWorks files.

22.6. DESIGN LIBRARY 349

22.6 Design Library

This section lists a number of objects for printing. For each object, please provideboth the STL file and the CAD file that generated it, and picture of that object. Geta CAD or Geometric modeling program and design your own objects to print.

22.6.1 Test files

These are objects of various complexities used primarily for testing or calibrating thesystem. Please identify what aspect of the machine, tool or material this objectstests.

Picture STL File Description

1in cube.zip 1-inch cube

1in cylinder.zip 1-inch cylinder

1in radius dome.zip 1-inch dome

1in tall cone.zip 1-inch cone

22.6.2 Simple parts

These are relatively simple objects used by beginners to get started and explore thesystem.


Picture STL file Description

Cat Block.zip Cat STL Block

Car Block.zip Car STL Block

NOY Block.zip 50mm X 20mm X5mm block with5mm raised letters“NOY”

20mmBlockWith10mmHole.zip 20mm L X 20mmW X 10mm H blockwith 10mm diameterhole

30mmTriangularPyramid.zip 30mm H X 30mmedge Isosceles trian-gular base pyramid

KYBlock.zip 50mm X 20mm X5mm block withcutout letters “KY”

HollowCone.zip 30mm H X 30mm DX 2mm wall hollowcone

22.6. DESIGN LIBRARY 351

Picture STL file Description

OverlappingHearts.zip A set of overlappinghearts, two separateparts

Frisbee.rar ?mm H X ?mm DX ?mm Frisbee

Dog bone.zip 6.2in X 1.4in X 1.6insolid dog bone