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”[1] 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[2].


  • 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[3].



  • The usual suspects.


I am now in the possession of a Zen Toolworks 7x7x5 DIY kit and have assembled the Y axis.


  1. [1]Not sure, but I don’t think it’s actually etching without chemicals.
  2. [2]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.
  3. [3]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.

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