O-Ring Issue???

[BanksAg]

Can a bad o-ring cause issues like in this picture? Earlier in the week we were cutting fine, but yesterday afternoon randomly started having an issue where the cut sounded different, there were sparks flying across the top of the metal, and after the cut we found that it hadn't cut all the way through in places. We were cutting 16 ga on an Arclight table with a PowerMax 45XP and fine cut consumables.

I started with changing the electrode & nozzle. Same issue. Checked the air, and still have over 100 psi reading on the gauge at the back of the cutter. Tried switching to standard consumables & moving the ground clamp to the metal - same issue. Mach 3 is reading within a couple volts of the recommended voltage and the speed is pretty close to what the book says. Still thinking it was an air issue, I swapped out a new swirl ring. Same problem.

The last thing I tried was firing then stopping the torch. I put my hand around it while the air was still purging, and noticed air coming out around the top of the retaining cap. Swapped that out and have the same issue. The only part I don't have a replacement of is the o-ring. Could this be the issue, or am I missing something else?

Thanks in advance.

[motoguy]

This is a known, though maybe not common, issue with the Finecuts. I've heard explanations of metallurgical issues in the sheet, or thickness differences. I used to have the same issue. I found that lowering my cut speed 10% (and adjusting voltage to keep the correct height) fixed the issue. Another member here says he would slow his cut speed and increase voltage (over book) for the first 2500 inches of cut, then he could cut book rates.

Slowing the cut creates a bit more dross, but I'd rather deal with that than trying to salvage/re-cut a part.

[BanksAg]

Thanks. I had read that somewhere before too. We did try lowering the speed and adjusting the voltage; on the 16 gauge with fine cut that helped a little, but didn't fully correct the issue. I had a similar issue even when I switched to standard consumables & 3/16 plate. With standard consumables it cut through, but there was considerably more dross, and the edge was more beveled than normal.

I forgot to mention too, that I did pull out my feeler gauge to check cut & pierce height, and they were pretty close to book specs.

[steel 35]

Turn your torch off using the ports and pins settings in Mach, take your time and run the same program over; Watch the amps on the xp45s display without the torch firing. I think you may find something I see pretty often. That's how I check for it.

[Dana gear]

I agree with Motoguy, we have to operate our two CNC plasma tables with Hypertherm and Fine cuts at a slower travel speed then the Fine cut chart calls out for in that particular gauge of metal, we set our voltage different as well, cut quality is very good very little dross.
That said you should never have compressed air seeping out around the cup, replace your o-ring and recheck...

[jimcolt]

I do not recommend slower travel speeds.....that will cause a wider kerf, more dross, more chance of warpage. With Finecut consumables....which are very sensitive to different plate chemistry and sensitive to height....you need to run at all book settings but increase the cut height (arc voltage on some machines). The book says to cut at .060" height.....you will solve the non-penetration issue by increasing height to .075" or so (increase arc voltage until height is .075". Slowing down may work, but will create other issues. Jim Colt Hypertherm

[jimcolt]

Part of the torch body cooling in Hypertherm air plasma torches is a bleed of air around the top of the retaining cap. It is normal. Certainly though, a bad torch body o-ring could seriously affect cut quality as well. Jim Colt Hypertherm

I agree with Motoguy, we have to operate our two CNC plasma tables with Hypertherm and Fine cuts at a slower travel speed then the Fine cut chart calls out for in that particular gauge of metal, we set our voltage different as well, cut quality is very good very little dross.
That said you should never have compressed air seeping out around the cup, replace your o-ring and recheck...

[motoguy]

I do not recommend slower travel speeds.....that will cause a wider kerf, more dross, more chance of warpage. With Finecut consumables....which are very sensitive to different plate chemistry and sensitive to height....you need to run at all book settings but increase the cut height (arc voltage on some machines). The book says to cut at .060" height.....you will solve the non-penetration issue by increasing height to .075" or so (increase arc voltage until height is .075". Slowing down may work, but will create other issues. Jim Colt Hypertherm

Increasing cut height/arc voltage alone didn't fix it for me. I had to decrease speed by 10% for it to go away. I already cut at .075, based on your previous recommendations.

[Dana gear]

Same here Increasing torch height / arc voltage was not enough, we plasma cut well in excess of 240 tons of 14 and 12 gauge hot roll.
All sheets are 48"x120" laser quality completely clean /flat sheet. We cut between 18 to 120 pieces out of each sheet.
Slight dross, absolutely no warpage. Using Fine cuts ,We have experimented with different parameters and came up with what works best for us.

[BanksAg]

Thanks for all of the advice. I talked with Arclight and he recommended replacing the shield. I had forgot that I had an extra so I tried that. I only did one cut with that, but it worked fine. I haven't cut enough to say that that fixed the issue.

We were going to try it some more yesterday, but the air compressor had other ideas. When I got into the shop in the morning my air compressor pump was on the verge of burning up, so it will unfortunately be a while until we get back to using the table again.