Design Realization lecture 9

John Canny

9/23/03

Last Time

More on kinematics and IK.

Some concepts from dynamics.

This time: Manufacturing & Materials

Manufacturing is undergoing a revolution: Traditional methods:

Casting, molding, fusing, slumping Milling, lathing (non CNC-versions) Stamping Rolling, extrusion

Shape is “write-once” (not programmable) in these methods.

Next-wave Manufacturing

Reprogramming shape: CNC machining:

A computer outputs a path for a cutting tool to create a specified surface.

Not new, but now inexpensive, PC-based.

Plastics, wood, metal, glass.

Flashcut 2000, XYZ-axes, 9x7x6.5”, $2895

Milling

Milling involves a moving XYZ head that cuts into the workpiece:

Bits can achieve differentfinishes.

Lathing

Lathes cut circularly symmetric parts. Shafts, furniture, fasteners,… lenses. Can also do grinding and polishing.

Milling Example

CNC milling example (Deskproto web site)

Finish is quite smooth ballnose cutting tool.

Lots of waste, but can be recycled!

Next-wave Manufacturing

PC-boards: Created with CAD tools. Photographic reproduction:

• Low cost in volume. • High complexity possible.

Multi-step process, BUT: Web-based services have 24-hour turnaround,

low cost.

Next-wave Manufacturing

CNC Laser cutter: X-Y axes control a powerful laser. Fine line (0.007” or better). Positioning to 1000 dpi, Some control of depth:

• Engraving as well as cutting.

Moderate cost:$10,000 Versalaser 16x12” workspace.

Laser Cutter Capabilities

Precision is good enough to make smooth sliding surfaces (gears).

Layering can be used to make3D surfaces (very popular for architectural models).

Can even make PCBsby etching metalfrom clear plastic!

Other 2D Cutting Technologies

Lasers can cut metal, but not easily Power limits, need to deal with

material removal.

Plasma cutters use an electrically-generated plasma jet to cut Sweeps away material.

Plasma Cutters

Thin shapes in a variety of metals. Torchmate 3 machine

is $10,000 for 4x8’workspace.

Water Cutters

Similar idea to plasma but based on high-pressure waterjet.

Cleaner method: water plus metal can be collected.

Cost??

3D printers

A variety of 3D printing techniques have appeared in the last few years.

SLA: Stereolithography: laser curing of liquid plastic.

SLS: Selective Laser Sintering: similar, laser fuses powder.

LOM: Layered Object Modeling: laser cuts paper one layer at a time.

FDM: Fused Deposition Modeling: a thread of plastic is melted through a moving head.

Stereolithography: SLA Earliest 3D method, based on UV-set polymers. Resolution quite good: 0.002” layers. Curing needed before

part can be used.

LOM: Laminated Object Modelling

FDM: Fused Deposition Modelling

FDM is one of the most versatile 3D methods Many materials can be used:

solvent-based or thermo-plastics.

Requires X-Y-X motion (like a CNC machine).

Stratasys machines start at $30,000

Roll-your-own 3D Printers

Material feeding heads are commercial modules. Microfab makes heads for

solvent-based and thermo-plastics.

Add a CNC XYZ-stage to create your own printer.

Roll-your-own 3D Printers

Polymer electronics is printable with microfab heads, working on actuators.

Potential for printing complete electro-mechanical systems.

Two prototype printersat Berkeley.

3D Printer Disadvantages

Slow! Adding material is much slower than removing it.

Speed scales very poorly with resolution: double resolution and decrease speed by 8x.

Laser 3D methods faster (than other heads) for equivalent resolution, but limited materials.

3D Printing Data

The standard 3D printing format is “STL”.

Available as an output option for most CAD tools, as a 3rd-party translator for Maya.

Then process-specific CAM software (Computer-Aided Manufacturing) creates a tool control file: Tool path for milling and lathing. Slices and support structures for 3D printers.

Summary

CNC machines provide shape programmability. Lathes and mills provide traditional shaping. Layered methods can create almost unlimited

shapes, but slowly. 2D and 3D shaping methods generally based

on CNC motion of an active head. Architecture of shaping machines is open:

movement and heads are available separately.