What is a CNC Machine?
A quote from www.thomasnet.com states, “CNC
machining is a process used in the manufacturing sector
that involves the use of computers to control machine tools.
Tools that can be controlled in this manner include lathes,
mills, routers, and grinders. The CNC in CNC Machining
stands for Computer Numerical Control.” Other machine
tools that fall under the CNC category are
plasma/laser/water cutters, 3D printers, welders, pick and
place machines, etc.
In the Beginning, There Were Hand
and Power Tools
What makes a CNC router so different from other
tools? First, it can perform many of the same jobs that
hand and power tools do — routing, drilling, sawing,
Secondly, CNC routers are well known for their
accuracy and repeatability. The accuracy of a CNC router
can fall within a few ‘thousandths’ of an inch. The
repeatability factor allows you to make 100 pieces of the
same part and have each one come out an exact copy of
the first one. Imagine how tiring, tedious, and time-consuming that would be using simple hand and/or power
Where Do I Begin?
On the software side, you’ll need three programs: CAD
(Computer Aided Design), CAM (Computer Aided
Manufacturing), and CNC. Refer to Figure 1a.
The process of designing a part for your CNC router
begins with a CAD program. Whether it’s a few wooden
gears needed to build a mechanical wall clock, robot, or an
anemometer, a CAD program can help you create just
about any size gear pattern.
Once the gear drawing is finished, you “Export” or save
the 2D drawing as a “.dxf” file (ASCII text file, NOT a binary
file). Other file extensions can be used, but .dxf has become
more of a standard file format for exchanging 2D drawing
files between CAD and CAM software.
The next step is to open the CAM program and import
the .dxf file. The CAM software will take the file (gear
pattern) and create what is known in the CNC machining
industry as a “toolpath.” A toolpath is just a series of X, Y,
and Z movements the router’s cutting tool must follow to
make a part.
The next operation for the CAM software to perform is
to generate a “G-code” program file based on the toolpath
of the gear pattern. A G-code program is a list of the X, Y,
and Z toolpath coordinates the CNC software (Mach 3) uses
After moving into a larger house and basement, I finally decided to
design and build a desktop CNC router. I spent a lot of time
researching CNC routers online. As everyone knows, working online
late at night can suck the life out of a human faster than a vampire.
Nevertheless, I survived and finally finished building my desktop
Beginner’s Guide to
CNC Routers By Roger D. Secura
46 SERVO 02.2018
If you’ve been mulling over the idea of building a
CNC router, I should warn you the learning curve is
quite steep. This article is my attempt to flatten out a
very small part of that learning curve by describing
the basic hardware and software requirements for
building a CNC router. Later in this article, I will try to
demystify some of the concepts, terms, and
operating procedures associated with CNC routers.
Although I’ll be referring to the Mach 3 CNC
program throughout this article, the concepts and
procedures presented here are general enough to be
applicable to some of the more popular CNC