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toolpaths with computer-aided manu-
facturing (CAM) software. This involves
specifying the dimensions and location
of the stock material, the dimensions
and characteristics of the end mill (cut-
ter), and speeds for the axes and spindle.
The tools to do this tend to be complex,
and a bit daunting for the first-time user.
If creating small 3D objects is your goal, a 3D
printer is the right choice.
DIY CNC
Going with milling doesn't mean you have
to give up on self-replication or on making
your own machine. Patrick Hood-Daniel, au-
thor of
Build Your Own CNC Machine
, makes
a scratch-build CNC kit capable of making all
of its custom parts, just like the RepRap 3D
printer and its progeny. The frame is built of
custom-cut plywood. Everything else is stan-
dard hardware.
The aluminum angle, bolts, and screws are
available from any hardware store. The lead-
screws and anti-backlash nuts will probably
have to be mail-ordered from McMaster-Carr
and DumpsterCNC, but you can get by with
lesser hardware store parts in a pinch. The
stepper motors and stepper drivers are com-
pletely generic and available from countless
sources. The spindle is an ordinary wood
router. I use a Porter-Cable 892.
As with the RepRap, the trick with Patrick's
CNC router is getting a seed unit. Fortunate-
ly, any CNC router that can handle a 2'×4'
sheet of plywood is capable of making the
parts. Check out your local hackerspace,
TechShop, Fab Lab and even the MAKE fo-
rums or the Home Shop Machinist, and
you're likely to find somebody local with the
necessary equipment. (If you can't find any-
body to cut the parts for you, Patrick sells
several kits.)
From the user's perspective, CNC milling is a
much more complex process than printing
is. CNC milling does, however, have a signif-
icant advantage over 3D printing: the tech-
nology is mature. Home 3D printers are im-
proving at a tremendous rate, but there's
often still a lot of tinkering and experimen-
tation involved in getting a good print.
What Do You Want to
Make?
If your interests tend toward larger and more
structural creations, go with milling. Also
consider that it's cheaper to work in wood
than in plastic, and that you're likely to get
substantially superior results.
On the other hand, making complex 3D ob-
jects is a lot more complicated with CNC
milling than with a 3D printer. There are free
tools for doing 2.5D milling, but CAM soft-
ware for 3D milling can be very expensive
and difficult to use.
Doing 3D work for 3D printing is much easier.
You can design your models in a free pro-
gram like SketchUp or Inventor Fusion, and
then export an STL file. Slicing software con-
verts the STL file automatically to toolpaths
in G-code, then sends the G-code directly to
your 3D printer. With 3D printing, there's no
need to tweak cutting paths, and no worry
about the tool crashing into your work.
Plans Avaliable from
Buildyourcnc.com
To get the CAD and CAM files for the parts,
and download the plans for the CNC Routing
Machine Kit Version 1.3. Videos on the
