I was under the impression that hpgl is too heavy for PICs. The smallest
thing I saw doing hpgl was a Z80 based system that read data from audio
tape cassettes and drove 3 1/2 axes for PCB drilling and hole-machining.
This was oooold.

However, I know that the machines that interpreted the old-style CNC
languages were extremely dumb, much more so than a PIC. So, if one would
take a PIC and teach it to receive Gerber format in ASCII over a serial
link, one co-ordinate set at a time, and move 3 motors and a speed
controller, then a reasonable CNC drill/mill station for PCBs would result
imho. Using relatively dumb controllers, a torque feedback sensor for the
vertical axis, and some precise end sensors, this could turn out pretty
good.

It could take Pcb drill output files directly and beep the operator to
change the bit when required. A neat but time-demanding PIC project.

Peter