[mchuhn]

I built a 5' x 10' plasma table using a Bulltear gantry kit and CandCNC BladeRunner controls back in 2012. Here is the build thread (https://www.cnczone.com/forums/bullt...al-rotary.html). It has mainly been used for prototype and limited production work. According to the Hypertherm display it only has 21 arc hours. Over the past year the cut quality has been slowly getting worse. There has been more dross and edge angularity then when it was new. It has gotten to the point where most parts are unusable. The nozzle and electrodes have been changed regularly. A refrigerated air dryer was added about 6 months ago without much change. I have even gone to pickled and oil sheets to avoid mill scale. Recently, all the torch end consumables were replaced including the cap, shield, swirl ring, and the cap O-ring with no improvement. Next, I contacted Hypertherm tech support to see if they had suggestions. Bob Churney, at Hypertherm, suggested it may be an issue with a lack of air pressure or a stuck pilot arc IGBT. I troubleshot both ideas without finding fault with either.

I just cut some parts from ¼” plate and there was a new strange cut. One edge of the part had a convex shape where the opposite edge had a concave shape.
With ¼” plate I used to get beautiful dross free cuts with no cleanup required now I get this or worse. I have played with torch height volts, both up and down, with no improvement. I have done the same with cut speeds with no improvement. Maybe related the torch height control has always had issues with thinner metals and finecut consumables. It will dive on larger cutouts. Any suggestions would be appreciated.
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[Jim Dawson]

An air leak in the torch hose maybe?

[mchuhn]

Jim thanks for the quick reply. Strange you mention that. Bob from Hypertherm suggested that as well. Do you have personal experience with this problem? I did turn on the air through the hose using the Hypertherm service display but I didn't hear any leaks. Perhaps I should check with soapy water.

Any other possibilities to check? This problem is progressive, gets worse with time, which would normally indicate a mechanical issue and not electrical but anything is possible.

Thanks,

Mike

[Jim Dawson]

No direct experience, but I was talking with a friend a while back who had a similar problem. Turned out there was an air leak somewhere near where the air hose connects to the torch. I think it was in the upper end of the torch. I know he fixed something that Hypertherm said was not repairable. Anything is repairable if you are clever enough

As you suggest, this is the type of thing that indicates a mechanical issue.