THC Seems to work, but not at the setpoint defined in material file?

Hello everyone!

I'm using a THCAD2 with QT/PlasmaC. I've verified the voltage conversions are correct in my configuration and started to run with the THC active. I noticed that it's moving up/down (I see the THC become active and up/down indicators flip on an off) but never gets to my setpoint (78v). Furthermore, it seems to actually be controlling to 100v (which it seems to achieve quite well). 

I'm using (I think) M190 Px to define the material parameters (configured in the GUI where I've set the voltage). Is this the wrong place to define the setpoint for the THC or is something else wrong?

Thank you!

Forget about your setpoint! Let the machine do its job for you.

With a good THC (like qtplasmac) we don't care about the actual voltage but we do care about the height of the torch so the arc is correctly positioned for the best cut. The voltage is a process control variable to monitor and control height. Generally we would enable auto sample so the actual voltage is sampled to set the setpoint after cutting commences

78 volts sonds too low anyway. 100-110 volts more realistic

If you want to lower the voltage, lower the torch but 20 volts could be a stretch.

Thanks for the advice!

My 78 volt setpoint comes from the hypertherm cut tables for my consumables / material / supply, so maybe that's where I'm being led astray.

So if I understand correctly it doesn't use my setpoint from the material, but samples after a pierce and uses that voltage for THC? So to adjust my actual cut height I'd use the cut height parameter and not the voltage parameter?

My cuts are seemingly too high so I wanted to lower it, I'll take a look at the sampling settings to see if that's how it's configured for me and adjust accordingly. Thanks!

A lot of your questions are answered in the Plasma Primer. Please read it
linuxcnc.org/docs/2.9/html/plasma/plasma-cnc-primer.html