That sounds like a perfect match to doing THC. Thank you, that will be what I try for my CNC plasma project.
Back on the questioning the viability for the Duet as a controller for an EDM machine. Would it be possible to have this control loop apply to more then just Z axis position but have it control movement along a path. Think if it have a analog voltage as the feedback this controls how fast the machine moves along a path. If it overshots it may need to backup. The output of the EDM power supply is an analog voltage related to the arc condition and a serial port to configuration and status information.