I have a Hypertherm 600 that I'm having problems with. I'll be cutting and all of sudden the arc gets real weak and stops cutting. Even on sheet metal it'll just leave a little "trench" in the metal. There's still an arc, just not strong. I've changed out consumables-twice- and it still is doing it. Sometimes it'll start in that condition, other times in the middle of cuts. What could cause that? Should I look at my air source? I have a desiccant drier on it, but I would think if that's bad, it wouldn't cause intermittence.