A CNC MILLING MACHINE
FOR LESS THAN A GRAND
By Tom Owad
THE OBJECTS WE BUY TODAY ARE MADE provide the motors and the circuitry to control them.
in enormous factories, typically thousands of There are many boards, called stepper drives,
miles away. Like the mainframes that preceded available to control stepper motors. My favorite is
personal computers, these factories are filled with the Microstep by EAS ( embeddedtronics.com).
expensive machinery, controlled and maintained by EAS sells the bare circuit boards and the PIC chips,
dozens of operators and technicians. Also like the and provides parts lists for ordering the rest from
mainframes, they’re about to be displaced by home Digi-Key. They even provide the source for the PIC
machines. and layout for the printed circuit board, if you’d
Neil Gershenfeld of MIT’s Center for Bits and Atoms rather do everything yourself.
has written Fab, a book that describes the possibili- An easier and more popular option is the Gecko
ties that home fabrication machines will create, and Drive ( geckodrive.com). This comes fully assembled
how people today are using fabrication labs that the and supports more powerful motors than the EAS
Center created. A critical component of personal fab- Microstep. Both options require an unregulated
rication is CNC — computer numerical control. A CNC linear power supply. These are about as simple as
machine is controlled by a computer that issues a power supply gets, and are easy to build.
commands for each movement the machine makes. The stepper drives can be controlled by an ordi-
One of the machines most commonly adapted for nary onboard PC parallel port, but if you use a PCI
CNC control is the milling machine, which resembles parallel card, you reduce the risk of damaging your
a drill press with a movable table. The table has x motherboard. EAS and many others sell parallel
and y axes that are controlled by motors. Using a port breakout boards that make it easy to interface
language called G-code, the programmer can direct the stepper drivers. To control the machine, there’s
these motors to move to a particular location, Enhanced Machine Controller or EMC ( linuxcnc.org),
traveling on a defined path at a defined speed. The a very powerful open source controller that can
z-axis is the spindle (or the table) and can be raised convert G-code into motion.
or lowered to adjust the depth of the cut. Fourth You now have an entire CNC mill, if a simple one.
and fifth axes can be added to rotate the work. The costs pencil out as follows:
A commercial CNC milling machine will cost from
$10,000 to well over $100,000 — but retrofitting $500
a manual mill will give you a home CNC mill for a $100
fraction of that cost. $100
The Sieg X2 is a very popular mini mill for CNC $100
conversion. Made by Sieg and marketed by Grizzly, $25
Harbor Freight, and others, it sells for about $500. $265
The simplest CNC conversion you can do with it is
to automate the x and y axes, leaving you to manually adjust the spindle to the desired level. In this
configuration, the x and y axes are controlled by
stepper motors that are mounted in place of the
handles. You can make the motor mounts using
your mill or you can buy a mounting kit, such as the
one sold by littlemachineshop.com (part #2668).
This provides all the brackets and couplings you
need to mount your motors. It’s still up to you to
Stepper motors ( 2)
Microstep drives ( 2)
Mounting kit (optional)
So, about $825 and a lot of dedication will get you
a basic home CNC milling machine that can cut
metal, plastic, wood, and circuit boards. A fun first
project might be to build your own wooden clock:
Tom Owad is the owner of Schnitz Technology, a Macintosh
consultancy in York, Pa. He spends his days tinkering and
learning, and is the owner and webmaster of applefritter.com.
92 Make: Volume 11