Scan2CAD is used throughout the CNC process -- from sketch, to CAD design and finally, fabricated in CNC! This document walks you through the most common design approaches. Our experts also shared 8 top tips that you should take note of when designing for CNC (scaling, overlapping objects and more!)

1. This guide is brought to
you by Scan2CAD,
the market leading file
conversion and editing
software
Top 8 Tips to Take
Your Design from
CAD Drawing to
CNC Fabrication

2. Table of Contents
▪ What is CNC?
▪ The Design Process: From Design to CNC
▪ 8 Tips for Designing for CNC
▪ Using Scan2CAD to Convert Images for CNC
▪ Case Studies: Reverse-engineering CNC parts

3. What is CNC?
SOURCE: technologystudent.com/cam
Computer Numeric Control
The computer converts the CAD design
into numbers – graphic coordinates –
which control the movement of the cutter.
In the diagram on the left, the cutter is at
point A (18, 8, 23). The computer-controlled
cutter will travel to different sets of
coordinates, in sequence, until the
desired shape has been manufactured.

4. CNC cutting in action…

5. Some of the most common types of CNC machines…
Type of CNC
machine
Plasma cutter
Laser cutter
Description
▪ Cuts material by flying across the
cutting table with a plasma torch
(instead of moving a spinning tool over
the material).
CNC routers
Milling
machines
▪ Perform complicated cutting operations
like rabbeting, routing, drilling, slot
cutting and threading
▪ Cuts wood, plastics and sheet metal in
3 axes (X, Y and Z). This allows cutting
of basic profiles.
▪ A similar principle to the plasma cutter,
it uses a laser. Both of these cutters are
used to cut 2-dimensional profile
shapes.

6. Table of Contents
▪ What is CNC?
▪ The Design Process: from Design to CNC
▪ 8 Tips for Designing for CNC
▪ Using Scan2CAD to Convert Images for CNC
▪ Case Studies: Reverse-engineering CNC parts

7. From CAD design to CNC fabrication…
It all begins as a drawing in
CAD software. The design
is usually saved as a 2D
DXF or DWG.
Import your drawing into
CAM software to generate
the toolpaths and G-code.
SOURCE: grzsoftware.com
Run the G-code on the
CNC machine software
and watch your design
come to life!
There are a few ways you can create your CAD design. In the
next two slides, we’ll walk you through the most common
workflows.

8. Example 1: Create vector cut paths by manually tracing
an image in CAD
SOURCE: freedxf.com/blog
We’ll start with a
photograph of a tractor.
Trace around the silhouette
and the main features that
you want to cut out.
Save your design as a DXF
file and import it into a
CAM program to generate
the G-code.

9. Example 2: Automatically convert an image into vector
for CNC
Scan your sketch and save it
as a PDF or image format (e.g.
JPEG, TIFF)
Convert the file to DXF format
using conversion software like
Scan2CAD
Import the vector DXF file into
a CAM/CNC program to
generate G-code
You can also convert and image directly to G-code formats in Scan2CAD

10. SOURCE: bobcad.com
Nope! Just import your pictures or CAD drawings into the
CAM software and the program will then generate the
code to make your parts.
All you have to do is make a few
selections such as:
▪ How deep the cut should be
▪ What feeds and speeds to use
▪ How to enter and exit the cut
▪ How many steps down to take
Some CAM programs can even
simulate the entire CNC machining
process!
Do I need to learn a programming
language like G-Code to operate CNC?

11. Table of Contents
▪ What is CNC?
▪ The Design Process: from Design to CNC
▪ 8 Tips for Designing for CNC
▪ Using Scan2CAD to Convert Images for CNC
▪ Case Studies: Reverse-engineering CNC parts

12. 1. Don’t forget to define the scale of your vector image
For precision CNC work, it’s good practice to set the system units to millimeters; and
precision or tolerance to 0.5 µm. Scan2CAD has three different ways to scale vectors
when exporting them to DXF file format. Check out this article in our User Manual to
learn more.

13. 2. Place your geometry on a single layer
After designing your drawing, you should make sure it is ready for CNC.
For best results, you should:
▪ Reduce the vector lines to the lowest number of nodes without being
detrimental to the design quality.
▪ Only export the relevant parts of your drawing into the final DXF file
▪ If you need to edit in your CNC software, lock layers that you don’t
want to accidentally select or move around

14. 3. Convert splines
CNC machines can work with polylines (made up of lines and arcs),
rather than compound curves like Bezier curves, splines and ellipses.
In Scan2CAD, you can convert splines into a polyline using the vector
editing tools.
▪ Select Vector Edit Menu > Modify > Bezier to Line
▪ Click on the Bezier curve you’d like to convert

15. 4. Remove spaces and draw one coherent cut path
If you want clean, connected cut lines,
then you must ensure that your relevant
vector lines are connected. This is
especially important when you turn lines
and arcs into polylines. Make sure that
the lines and arcs join together perfectly
by using Snap tools (do not
approximate!)
AutoCAD users would find the PEDIT
command handy for this purpose. In
Scan2CAD, you can define a Grab Snap
Distance between grab points.

16. 5. Select touching objects and convert them into a
single entity
In Scan2CAD, select the Vector Edit
Menu > Modify > Make Polylines.
▪ If there are arcs in your drawings, you
must check Include Arcs before
converting them into polylines. This
function is found by clicking Vector
Edit Menu > Modify > Polylines
Options > Include Arcs.
▪ How do you tell what line types your
drawing is made up of? In Scan2CAD,
you can view vectors by type. First,
make sure that View Vector Colors is
switched off (by pressing the C key on
your keyboard). Polylines are
displayed in green, while arcs are
displayed in magenta and lines in red.

17. 6. Remove overlapping geometry
If there are overlapping vectors in your design, you’re basically instructing
the CNC machine to go back and forth in the same area. This is may be
OK for some laser etching designs but in most cases it is not practical.
▪ Delete any potential overlapping duplicates of vector objects
▪ Combine lines that partially overlap (for example, arcs drawn over
portions of circles)
▪ Combine objects when aligned end-to-end
7. Set your default Z-Axis value
In Scan2CAD, you can set the default Z value for all vectors in the CNC
export options. (File > Vector > CNC Export Options)
You can also set the Z value for individual vector elements should you
wish to.

18. 8. Familiarize yourself with the cut width of tools on
your CNC cutting system
The depth and width of cut are crucial variables when milling pockets, profiling, facing
and performing other machining operations. Understanding your cut width will help you
control your feeds and speeds, the Material Removal Rate and how long it will take to
complete the operation; as well as the surface finish.
The spacing between your
toolpaths should be comparable
to the diameter of the tool.
Also take note that machined
corners depend on the size of
the end mill, and this affects how
to parts fit together.
To learn more about CAD and
milling strategies, check out this
guide to Mastering CAD and CAM
for CNC Machining by Michael
Zalewski.

19. Recap: 8 Tips when Designing for CNC
Define the scale
of your vector
image
Place your CNC
geometry onto
a single layer
Convert splines
into polylines
1 2 3
Remove
overlapping
geometry
Set the default
Z value
6 7
Remove spaces
to draw one
coherent cut
path
4
Familiarize
yourself with
cut width of
CNC tooling
8
Select touching
objects and
convert them
into a single
entity
5

20. Table of Contents
▪ What is CNC?
▪ The Design Process: from Design to CNC
▪ 8 Tips for Designing for CNC
▪ Using Scan2CAD to Convert Images for CNC
▪ Case Studies: Reverse-engineering CNC parts

21. Why use Scan2CAD to prepare your CNC drawing file?
You could trace an image manually… … or convert that image automatically!
…compared to a one click process!Lots of fiddling about with pens and grab points…
 Load the image file into a raster-to-vector
conversion program like Scan2CAD. A
few clicks later and voilà! Out comes a
DXF file that’s
ready to edit in
CAD software.
 You could manually redraw the vector
file. This could take hours, or even days
– time that could be better spent working
on other things!

22. Converting your image to DXF is easy with Scan2CAD!
2. Select the conversion settings. Scan2CAD comes
with pre-programmed settings for each type of image.
For CNC we recommend ‘CNC Profile’ or ‘Picture/Photo’
1. Load the image or PDF
file that you’d like to
convert.

23. Voilà! 4 steps to producing a DXF file for CNC
3. Click “Convert”. Wait a few seconds and voilà!
You have a DXF file that is compatible with any
CAD software on the market. After conversion,
you can choose whether to display only vector
information or to overlay the original raster image
as well.
4. Save the DXF file. Now, you
can edit and clean up the DXF
file with any CAD program,
before importing it into CAM
software.
Tip:
Tip: You can also save in a G-code
formats (.nc, .cnc. .tap)

24. Once the image is converted into DXF, you can easily
edit it using any CAD program
The Scan2CAD vector editing toolbox offers all the basic functions:
 You can cut, copy and paste certain elements of an existing drawing.
 You can edit specific elements of the drawing, including stretching vectors, converting lines to
arcs, and more.
All sorts of
CAD editing
tools in your
arsenal!

25. Table of Contents
▪ What is CNC?
▪ The Design Process: from Design to CNC
▪ 10 Tips for Designing for CNC
▪ Using Scan2CAD to Convert Images for CNC
▪ Case Studies: Reverse-engineering CNC parts

26. Case study: Reverse-engineering CNC parts
Who?
Shapemakers is an Australian CNC company that manufactures an A0-size
scanning system called Deskan Color Express 6. Its clients turn to Shapemakers
to scan old gaskets, drawings and seals (up to 1180x870mm in size!)
The Deskan 6 software can scan the A0 drawing in strips and stitch these
together using the proprietary software. However, its clients require the
drawings in DXF vector format for editing in CAD or cutting on a CNC
machine. That’s where Scan2CAD comes in. Our software allows Shapemakers
to vectorize their large scans and cut out the parts quickly and easily.
Who’s the user?
Why do they need
a scan-to-DXF
converter?
Here’s a sample of
their work
The Deskan
FastParts
reverse-
engineering CNC
solution

27. Scan2CAD is the market leading file conversion and
editing software
Download your free trial
Scan2CAD includes conversion tools, image editing and cleaning tools, smart OCR, full
PDF support, as well as vector recognition and editing. Click on the blue button to learn
more about Scan2CAD.

28. Features offered by Scan2CAD
 Automatically convert raster images to
vector (no manual tracing needed)
 Edit and transform your files with a suite
of vector editing tools.
 Have full control on your CNC file
including setting correct scaling and Z-
Axis values.
 Save as DXF or G-Code formats including
CNC, NC and TAP.
Perfect for CNC
 OCR - Convert text in images to editable
vector text.
 Batch convert – convert 1000’s of images
at once.
Many more features including:

29. Text
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