I came across the thread while looking for Mig info. Yes, I've built a lot of plasma gear in industry. As one poster said, things blow up during new product design. I destroyed a lot of parts. And permanently etched a lot of test gear when plasma went where it was not supposed to be.
The comp simulations showed great safety factors. Dimensional measurements seemed correct. On power up, BOOM, 2 weeks of work shot in 1/2 second. After reverse engineering the failure, it turns out there was one little metal burr where it should not have been.
The concepts are easy, the implementation is tough...