Problem with THC

Use halscope to do a plot of encoder.0.velocity pin during a pierce, might be interference, although as you are getting 55 and 75V readings it also seems not right, and this might be due to scaling and/or due to interference.
What divider ratio is Mesa THCAD set to? Usually 1/32.
If this is a new machine, disable auto volts, disable void lock and velocity lock, well disable everything automated until you get the machine working correctly, only then enable the automation.

I do not, i set automation off, play with voltage till i get roughly good cuts and THC properly tracking, sometimes a bit of editing the scale and offset to match the measured voltage (ranges from 97V to 135V depending on the source and nozzles), then:
- fine tune the cut height by changing the voltage in 2V increments up or down
- fine tune the feed rate
- fine tune the air pressure to get clean cuts on the bottom side (less dross)
All this should be done whenever changing material thickness/type, nozzle diameter/type, and/or plasma source eventually. Also will be influenced by the amount of moisture in the compressed air, sometimes enough to cause issues.
And i never use autovolts, mainly due to many external factors that i have no control over, like, huge power fluctuations, huge differences in material being cut, above mentioned moisture, old air compressors spewing oil through the torch, using old plasma sources with no current control, etc.
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Another thing that will absolutely mess with cutting is the ground clamp, it has to be properly bolted to the table, no clamp.