A CNC (computer numerical control) milling machine is a device that renders computer-created designs into solid material by precisely moving a drilling/routing tool according to digital instructions based on the designs. It could also be coerced to work like a plotter by replacing the drill with a pen, or possibly as a paper/vinyl cutter (like a Cricut) with a blade.
This happens to be the same thing as an X-Y table, except that a third Z axis is used to control the up-down motion a cutting or marking tool (a drill, router, pen, or blade), and all axes are controlled by computer using stepper motors.
In many ways, a CNC mill would serve as a rapid prototyping device—an item designed on a computer is sculpted or engraved from a solid blank. Wood, plastic, and styrofoam would be some easy possibilities.
A more intriguing possibility is that, if it’s precise enough, the machine can both “etch” and drill printed circuit boards. This would greatly simplify the process of constructing and testing new circuit designs, and remove the whole stupid iron-on toner transfer bit from the process.
- At least 6 × 6 inches in working area. A PCB wouldn’t require a great deal of clearance, but more room would be useful for cutting stuff out of other materials.
- Precise enough to scratch out lands at least small/dense enough for SOIC, but much preferably TSSOP and TQFP.
- The usual suspects.
I am now in the possession of a Zen Toolworks 7x7x5 DIY kit and have assembled the Y axis.
-  Not sure, but I don’t think it’s actually etching without chemicals. ↩
-  I’ve found toner transfers difficult to do right and hard to reproduce with decent results. I think this method has as much potential as presensitized boards, and this method doesn’t involve coated boards or developer chemicals. ↩
-  The basic footprint of TQFP44 in gEDA PCB has 0.40mm pads on 0.80mm centers (i.e. with 0.40mm spaces between each pair). This is consistent with the TQFP chips I currently have. ↩