by beefy » Fri Oct 18, 2019 10:43 am
In gcode "M3" is generally used to turn on the torch. In typical milling, routing, etc M3 is "spindle forward" and M4 is "spindle reverse", but for plasma think of M3 as "Torch Fire".
So if you go to the spindle setup section, you'll see port and pin number boxes where you can set your OUTPUT port/pin numbers for M3. I stressed output because you said, "input the pin for the torch on/off switch" yet you must output a signal to turn on the torch.
I use Sheetcam to generate my plasma gcode and (with the correct post processor) it will automatically insert M3 or M03 into the code wherever the turn is turned on.