Originally Posted by kylemp  Turn your Z acceleration way down.. |
Actually acceleration in motor tuning has no effect for THC moves. It is not used during THC moves, only during normal moves like the lift at the end (anything called from G-code).
The setting that will effect that is the THC RATE. It sets the percentage of THC velocity based on the max velocity set in motor tuning for the Z axis. Depending on the courseness of the Z drive (resolution) settings too aggressive in THC Rate can cause "head bounce" and other effects from a condition called "overshoot" where the torch cannot move in small enough increments to balance out the target volts (set by the knobs) with the actual torch volts.
If the THC rate is too high for the motor and drive type, it can force the motor to stall. The THC will see that the voltage is wrong and try again and the motor will stall again , (etc, etc). The telltale sign is the DRO for Z gets out of sync with where the torch really is. It obvious at the end of a cut and the lift is the wrong distance off the metal.
TOM Caudle
www.CandCNC.com