somewhere on the router table and designating it Machine
Zero (Figure 2). Next, they jog all three of the router’s axes
to the chosen location. This is where they mount three
SPDT switches (X, Y, and Z) onto the router’s framework.
It should be noted here that homing switches are not a
mandatory requirement in order to operate a CNC router.
However, since all X, Y, and Z coordinates are referenced
from Machine Zero, it might be important to you to have a
more permanent Machine Zero location on your table.
Danger, Will Robinson!
I feel obligated to warn all the beginners out there who
plan to build or purchase a CNC router. It is imperative that
you DO NOT insert any cutting tool (bit) into your new CNC
router UNTIL you are completely satisfied you understand
how to set up and operate your machine. Your inexperience
with CNC routers can damage your machine and/or cause
you physical harm.
Here are three steps I suggest you follow for your own
• To be safe, take a toothpick and use it as a substitute
for a cutting tool. Just twist the toothpick into
one end of a new pencil eraser as shown in
Figure 6 and Figure 7. This will allow you to
“play” with your X, Y, and Z axes and see if
you really know what you are doing without
damaging your machine or injuring yourself.
The sharp end of the toothpick will also help
to pinpoint all the important locations on your
table (Machine Zero, Work Offsets, etc.).
• Run a CAM Simulator program that
employs animation to show you how the gear
will be routed on your CNC router. This will
give you a chance to see on a computer screen
if the gear program (G-code) has any routing
problems. Some CAM programs have this
feature. Mach 3 also has a rudimentary
toolpath simulation feature.
• Run your gear program (G-code) in
Mach 3 without anything inserted into the
collet (chuck). In other words, turn off your
spindle motor and let your router do a dry run
(i.e., “cut air”). As the gear program runs,
watch the collet and see if it looks like it’s
following the gear pattern as it moves through
the air above your workpiece (wood).
All CNC machines (mills, routers, lathes,
etc.) come equipped with a big red emergency
stop button (E-Stop). So should yours! Remember, if this is
your first experience with CNC routers, ALWAYS keep a
finger on the E-Stop button when your CNC router is in
operation, just in case something unexpected happens.
All you need is a ruler (1/32”) to calibrate your
machine. One axis at a time, you position (jog) the X, Y,
and Z axes to the edge of the ruler. If you go to the
Settings tab in Mach 3, you’ll find the ‘Set Steps per Unit’
button. Just follow the prompts and Mach 3 will guide you
through the process.
The Finish Line
I barely scratched the surface of what you need to
know about CNC routers. I hope you learned something in
this article that you can use with your new CNC router.
Stay safe! SV
Figure 7. Figure 6.
52 SERVO 02.2018
Tip #4: SET STEPS PER UNIT! It’s extremely important
that you calibrate your router so that when Mach 3
“says” it moved the X axis one inch on the DRO
display, it has actually physically moved the X axis
one inch on the router table.