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Modeling Basics for 3D Printing Using AutoCAD®

William WorkCAD Manager

Who am I?

Architect CAD Manager

I am an architect and CAD manager with a firm of more than three hundred professional staff working on projects spanning a wide range of project types. On a daily basis, I work closely with the design staff providing impromptu one-on-one Q&A style AutoCAD® support and tutorials. On a regular basis I develop and deliver structured classes. I have also worked directly with resellers providing a variety of consulting services throughout the United States. These services have included AutoCAD deployment and customization, on-site training, and CAD standards development and documentation.

What’s in it for you?

My goal is that you will:

Understand the fundamentals of 3D printing. Be able to create 3D geometry that is suitable for 3D printing. Validate your 3D model. Output the required STL format file.

We’ll do all of this entirely within AutoCAD!

How Will We Get There?

The first part of my talk will be an introduction to the 3D modeling capabilities of AutoCAD particularly related to 3D printing. Along the way I will demonstrate some of the fundamentals.

The second part will be a step by step case study of the creation of a 3D model for 3D printing.

But first…

“…,the most transformative technological innovation of our time,…”Hemispheres Magazine, November 2014

Why Use AutoCAD For Creating 3D Geometry?

AutoCAD fully supports 3D geometry.

AutoCAD’s 3D command set is robust.

You don’t need to learn another software application.

You don’t need to purchase another software application.

The Basics of 3D Printing

What is 3D Printing?

3D printing is a fabrication process whereby an object is generated directly from a 3D computer model.

It is an additive process that lays down successive layers of material under computer control.

The input to the 3D printer is an STL file that you generate from your 3D computer model.

Best Practices

Modeling for 3D printing is not fault tolerant.

Faces must meet cleanly.

The model must be watertight.

Small elements will need to be exaggerated.

The model must be one piece.

Your AutoCAD Workspace

Make the 3D Modeling workspace current.The handout lists ten useful system variables. Here are two important settings.

Osnapz=0Prevents osnaps from auto-projecting to the XY plane.

Solidcheck=1Turns on 3D solid validation.

Both of these are the default settings.

Visual Styles

Control how objects appear in a viewport.

Many times changing from one visual style to another will help you better understand your model.

Visual styles can be customized.

Vpcontrol=1 will display the control in the upper left corner of the drawing area.

The AutoCAD 3D Tools

AutoCAD’s 3D Modeling Tools

AutoCAD allows you to model using solids, surfaces, and meshes. In my experience solids are well suited to 3D modeling for 3D printing.

Closed meshes are also perfectly valid.

Surfaces are not valid for 3D printing.

We will concentrate on solids.

AutoCAD’s 3D Modeling Tools

Box Cylinder Cone Sphere Pyramid Wedge Torus

Polysolid

Solid Primitives

Think of the solid primitives as your basic building blocks.

Your model will often start with these and then you will manipulate them in various ways to achieve your desired result.

AutoCAD’s 3D Modeling Tools

Extrude Loft Revolve Sweep

Solids Generation

Solids can be generated from closed objects that define profiles.

Using these objects you can easily create many complex geometries.

AutoCAD’s 3D Modeling Tools

Union Subtract Intersect

Composite Solids

Composite solids are created by adding together, subtracting, or finding the intersection of objects.

Often the object you are modeling will begin with primitive solids and generated solids combined with each other.

AutoCAD’s 3D Editing Tools

Presspull Imprint Shell Fillet or

Filletedge Slice

Solid Editing

AutoCAD offers several commands to further edit your model. Use these commands to directly manipulate faces, edges, and vertices.

Cleaning and Validating Your 3D Model

Clean and Check options of the Solidedit command.

Clean

Clean removes redundant edges, vertices, and unused geometry from your model.

Check

Validates your model. If your model passes the check, this prompt is displayed: “This object is a valid ShapeManager solid.”

Creating Your Output File

Most 3D printers will want an STL file. Use the 3dprint command. That’s all there is to it.

Case Study

Case study: Doric Column

What follows is a step by step example of how a complex object might be built using the commands and techniques just described.

Step 1: Construction Guides

Establish the centerline of the column shaft.

Draw guides for the diameter of the shaft at both ends.

Divide the defining circles into 20 segments.

Draw guides for the radius and location of one flute at both ends of the shaft.

Step 2: Loft the shaft

Using the guides for the shaft, create the shaft by lofting.

Step 3: Loft the flute

Using the guides for the flute, create the flute volume by lofting.

Step 4: Array the flute volume

Using a polar array, generate volumes for the 20 flutes.

Step 5: Subtract the flute volumes

Using a Boolean subtraction, subtract the flute volumes from the shaft.

Step 6: Place spheres for the flute ends. Using the guides for the flutes,

place spheres at both ends of the flutes.

Step 7: Array the flute end spheres

Using a polar array, generate spheres for the 40 flute ends (top and bottom).

Step 8: Subtract the flute ends

Using a Boolean subtraction, subtract the flute end spheres from the shaft.

At this point the column shaft is complete.

Step 9: Shell the column shaft

To reduce the print time and the amount of material used, apply the shell command.Within the context of the command, remove the top face of the shaft.

Step 10: Capital and base guides

Place guides for the capital and the base in position.

Extrude the plinth is horizontally. Revolve the base moulding around

the center of the column. Extrude the abacus downward. Extrude the abacus moulding

around the abacus. Revolve the capital moulding

around the center of the column.PLINTH

BASEMOULDING

ABACUSMOULDING

ABACUS

CAPITAL MOULDING

Step 11: Completed project – but…

The column looks complete but would be more suitable for 3D printing if the capital was separated.

As it stands the column will require support material to handle the overhang of the column capital resulting in time spent for post-process cleaning.

Step 12: Capital removed

Remove and invert the column capital.

Created a stud within the column shaft.

Step 14: Final step

Subtract the stud from the column shaft. Note that the stud is keyed to ensure the proper alignment when the column is assembled.

Scale down slightly a copy of the stud and place it on the column capital.

The union command is applied to each model.

Sending the model to the 3D Printer The software application that comes

with the 3D printer allows you to arrange the model or models on the build plate for maximum efficiency.

Note that this application offers an estimate of the time and material required.

Final 3D printed column

Thank you for your time.

I hope this brief seminar has encouraged you to go forth and start exploring 3D modeling in AutoCAD.

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