Homemade CNC Plasma - hypertherm, Mesa, gear drives, nema 34.

Does the error trigger on pierce?

RNJFAB wrote:

Yes triggers on pierce. 

95% interference/shielding/grounding issue
5% brownout due to inadequate wiring in the shop and the subsequent voltage drop when plasma goes from pilot to cut
Since it was OK and lately developed this, first thing to check is shop grounding, earth dries up and does not conduct properly or at all.
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Had the same issue a few years back at a client, i kept telling him the above, but he did reject that as reasonable so i asked him to wire machine ground to the water line as i recalled he has metal water pipes in the ground, never ever complained again.
The grounding rods are way to close to the surface if this happens to be the issue.
For the 5%, use a DVM with memory and check where does the voltage fall to when plasma triggers.
Might also be the power supply caps are drying up.
For interference, a scope would be nice, but you can use a DVM set to manual AC voltage range and measure between GND points and metal case and/or metal machine parts. If you get any reading above 5-10V, that is not OK so grounding and shielding must be corrected. Although i have seen machines with 60V still working properly, but i would not risk it, ever.