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Modeling Basics for 3D Printing

Using AutoCAD®

William Work CAD 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=0

Prevents osnaps from auto-

projecting to the XY plane.

Solidcheck=1

Turns 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

BASE

MOULDING

ABACUS

MOULDING

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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