Modify gcode to suit plasma cutting

Tommylight is correct but I'll nevertheless contact Proma to see if there's a way around the problem. It's a polish company and their communication is not the best.]
I'll continue to make improvements available because there will be others out there with the Proma SD "stand alone" version.
Thank you both for your kind help.
Kind regards
Bruce

Do you think it would be possible to temporarily disable the Proma SD signals for the z axis by disconnecting the ground wire by means of an external relay (normally closed) triggered through the the 0-10v spindle speed output on my cheap Chinese bob using M4?

If you disconnect the ground wire while the plasma is on the Z axis will start vibrating violently and risk destroying the Z axis drive as that would leave the drive inputs open to interference.
It might be better to use the step and dir outputs from the Proma SD as encoder counter, something like :
Z axis wired to BOB not to PromaSD, PromaSD step and dir outputs to BOB inputs, use step pin as encoder pin in hal, use dir pin to change the counting up or down in hal.
A simpler or more complicated version ( depending on how good you are with electronics ), is to use two XOR (7486) and two FLIPFLOPS to have the step dir signals converted to up down.
Also using a charge pump for the step pin should work, again using the dir pin to change the direction up or down.

Thank you Tommylight. I'll have to give the matter some thought and will et back once I've done so.
Regards
Bruce