Z-axis/THC surging, jagged cuts

Hey everyone. I’m still relatively new to the cnc plasma world. Im currently having an issue with either the z-axis or THC.

I’m currently cutting 3/16 mild steel, running a Yeswelder Cut65, 70psi, 55amps, 35ipm, cut height is .05. I do a dry run every time before I run the final cut and the z-axis and THC run smooth. but as soon as I start a hot cut the z-axis starts bobbing, while it makes the cuts. even on long straight cuts it does it. all my cuts look like a serrated edge. But my very first cut on the machine after I 1st got it set up produced a very clean crisp cut, but by the end of that 1st cut it started doing what is does now. Any advice or help would be greatly appreciated

What happens if you disable THC? It’s probably not even necessary with 3/16 steel unless your gantry rail isn’t level.

Also, a cut height of 0.05 is pretty low. I’d increase that to at least 0.06 inch.

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