Torch height jumps up after cut starts

[_stevenmoore_]

Have Linux cnc command and got everything pretty much tuned in other than as soon as I start a cut the torch height jumps up about 3/4 inch and the cut just gouges the material then. If I run with torch disable it does not jump up.. I swaped to our back up plasma cutter and does the same thing.. pmw box has the right lights on. All good connections all ohmed out wires to be sure.. any help? The Linux guy is having a hard time and I'd like to have this going today or tomorrow.. tha KS in advance!

[Rodw]

I would ask in the Plasmac section of the Linuxcnc forum

My guess is either you have your height settings wrong or that you have Auto volts enabled and the THC delay is too short. Make it 0.5 sec to start with. You can see what is going on if you use halscope (linuxcnc's software oscilloscope) to measure torch voltage, torch on and THC enable signals.

[TJS]

What plasma unit are you running. Did you adjust the jumper on the back of the PWM module contingent upon your plasma machine. What DTHC do you have a IV or a V unit. Has the DTHC ever worked before properly without jumping up. Provide some more info if you can.

[Rodw]

What plasma unit are you running. Did you adjust the jumper on the back of the PWM module contingent upon your plasma machine. What DTHC do you have a IV or a V unit. Has the DTHC ever worked before properly without jumping up. Provide some more info if you can.

This isn't relevant. He's not using candcnc. The THC is managed by Linuxcnc internally. There is no external THC

[weldguy]

Do you have THC turned on? I would keep that out of the mix until your confident everything else is working 100%. THC can throw a real wrench into things when your first getting started.