Make: Technology on Your Time Volume 18

PERSONAL FAB By Tom Owad

Building a CNC Mill

There’s a lot of well-deserved excitement surrounding the RepRap 3D printer, and much of it focuses on the RepRap’s ability to make its own parts. The RepRap’s fabrication technique is additive — it uses a plastic extruder to “print” a plastic model, one layer at a time.

This contrasts with subtractive fabrication techniques, which start with a solid block of material and use a cutter to remove the excess.

Subtractive fabrication is far more common than additive, especially when working with metal and wood. Lathes, mills, saws, and drills are all subtractive tools. A CNC milling machine or router is the subtractive equivalent to the RepRap 3D printer.

For the hobbyist, milling is inferior to printing ...