rapid and extreme kerf angle changes

[esracerx46]

Im hoping someone here can help me out. I have a dynatorch 5x10 table and a thermal A-120 plasma. I have been having issues when cutting thicker plate (1/2"-1" thick). I have had these issues on and off for about the last year and a half or so. They went away for awhile but have come back. It has gotten the best of me and am hoping someone here can help. The people at thermal and dynatorch both have said they've never encountered this.

In the middle of cuts the kerf angle will change drastically and rapidly. The last piece of 1 inch plate went from 78 degrees to 91 degrees in the blink of an eye. This isnt a square where on side is goofy like the torch is out of square, rather it happens intermittently any direction.

I have purged all my air lines making sure there is no trapped water before it goes into my air dryer.
I have bipassed my air filter. Then my refrigerated dryer. Then my desiccant drier, putting straight shop air in.
I got a tank of breathing air from my distributor.
I put a flowmeter on just prior to air entering my plasma, and everything was OK.
Changed every consumable and O-ring I know about.
Bought a new torch thinking something was bad in the torch.
Upsized all the wires from my breaker to 4 awg.
Checked every but and bolt on the motors and and gantry, can't get it to wiggle even a little bit.
Inspected all The gears and bearings, nothing obvious.
Put a new ground on the power source.

I'm utterly stumped and its driving me nuts. This doesn't happen all the time, but seems to be more prevalent on thicker plate. I know 1 inch is pushing it for this machine, but I cut 1 inch for the first hear I had the machine and never had this issue.

If anyone has any ideas, anything at this point is greatly appreciated. My dad/boss thinks it computer or outside electric. By turning the THC off I think that would take any possible computer issue out of it. For what its worth, we are on what I have been told is a delta 3-phase electric system. 120,120,208.

[Shane Warnick]

Have you ever cleaned the inside of the plasma cutter itself? Does it have a cooling fan? If so, is it working? Almost looks to me like you are exceeding the duty cycle of the machine or getting real close to it, and perhaps you are losing some of the amps driving the arc in the middle of the cut. If you are asking for 80A or 100A, and then cutting at 8 ipm, (I think that was what I saw in the owners manual for your machine on 1" plate) it wouldn't take long to hit an 80% duty cycle (64 inches out of 10 minutes of cutting). Just a thought. May be exceeding or near exceeding the duty cycle, or perhaps the internals are full of plasma dust, shop dust, paint overspray, furballs / dust bunnies (I have never found any of that stuff in my Hypertherm I PROMISE ) or the fan is not working properly, and something is getting hot and losing efficiency in the middle of a cut thus causing power output to drop. There are only a few other things I can think of, one if that the machine speed is changing in the middle of the cut, at a speed that slow a 10% increase is would be a killer, the other is that there are inconsistencies in the material itself. There is a definite change in the wash pattern where the arc is washing the material out of the cut, and it looks slightly different as well in the middle of the plate. Sounds like you are sure your air supply is good, and is constant, so the other two variables are power output / return and the material itself. You stated you have upgraded all the wire from the panel for the power supply, make sure you check ALL the connections, if one is marginally loose and you get it hot during a cut the impedance will rise, could cause a phase to brownout so to speak and fade in and out on you, could cause some power fluctuations. Have you checked the ground? Ground connection to machine? Is the ground clamp just shot from arcing and having a bad connection and is sketchy to begin with? Ground cable intact and good? Back to the material, did you perhaps buy all of the thick material that has been giving you fits at the same time? Or all from the same supplier? Might want to consider picking up a piece of plate from another vendor and giving it a go just for giggles. If it all cuts fine and no problems I would say you could quit looking for the problem. Just some brainstorming, if I think of anything else I will let you know. If you chase it down, let us know that way if we run into the same problem we know where to start.

Shane

[jimcolt]

I suspect you are cutting some plate with some extreme magnetism. While many steel suppliers move plate using magnets.....and there is little or no residual magnetsim in the plate.....there are some types of plate that retain very strong magnetism in small areas. Often this is a caused by plate that is poorly produced with incorrect metalurgy.

Magnetism will push the plasma arc rather dramatically, and generally causes extremely short nozzle life as well.

Jim Colt Hypertherm

[esracerx46]

Interesting theory on magnetism and metallurgy. In the best, when asked I have been able to get material specs from our supplier. Perhaps if I find out where the plate has been manufactured will be more of a tell tale sign. The A-120 has been replaced twice in the 3 years we've had it. I didn't have the problem with the first machine, the second machine these issues arose about 6 months after I got it. I had it replaced for this reason since I couldn't get an answer out of anybody, after I tried everything they could think of.

I have had another issue that's about as intermittent as the angle irregularity and that's top edge rounding. I know typically that's from poor settings. But these are all settings I've never had a problem with. I don't have a picture of this issue but I'll try and describe it. I'll have a nice square cut where I can see the drag lines, then a slight change occurs where the drag lines go away, the edge feels slightly rounded, and has a shinier appearance. Sometimes this happens in the middle of a cut, but I see it more predominately after it turns a corner. I have not been diligent enough to notice if it is always the same direction or not.

In my manual for the A-120 it says to have a cut speed of 12 ipm at 100 amps. I stay away from 120 amps because of the duty cycle. I have found the 120 amp settings to be useless. Cutting so slow with a part that's relatively large, I'd hit the duty cycle before the part is even halfway cut.

This issue seems to happen more frequently the further along it is in the cut, which leads me the power direction. If everything is tight on my end, could I have an issue with the power I'm getting form the power company? If so how would I check that? I had Com-Ed come out once and he said it was fine, but I don't know what exactly he checked.

I'm not getting any arcing on my ground. The power source is also earth grounded in shop, as well as the ground outside the building. I checked both of those and didn't see any issues. It was suggested to make sure the ground was saturated enough, so I poured 15 gallons of water in a hole I drilled right next to the indoor earth ground.

I appreciate all the advice. I'd like to upgrade units, but If it is in fact a power issue, this will continue to haunt me.

[Dennis]

Looks to me like you got your electrode on the wrong side of the start cartridge , it shouldn't be coming through from the back.

[jimcolt]

Just see if a small piece of steel sticks or is attracted to the steel in the area that the cut was affected..to determine magnetism.

This type of issue is likely not a power problem. It could be air flow related......could something be restricting the inlet flow to the plasma on occasion? A piece of rust or teflon tape that is plugging an orifice or fitting somewhere? A slug of moisture periodically getting through your plumbing and into the torch?

Jim Colt Hypertherm ( a Powermax may help!)

[esracerx46]

If I knew what I know now about plasma systems I would have definitely gone the Hypertherm route. A few months after we got the original something happened. Took it to the repair center, he didn't know what was causing the error. I had talked to someone at thermal, and he then spoke to the repair center. I believe they diagnosed it as rubber snubbers. They were switching factories or something and weren't able to get them for 2 weeks, so they overnighted me a new machine. Kind of an ominous sign when a machine goes down 3 months after new.

I didn't notice any stickiness to the plate with a small piece of 16 ga. I had always assumed I had an air issue. My compressor is on one side of the shop up high and the air lines run down before coming into the dryer. I assumed I had water trapped in the valley of the lines before it got to the dryer. Now every day before I use it I unhook the lines before the filter and open the valve to blow out anything that might not make it up to the dryer. The first time I did that the problem went away, but again it had been intermittent, so I don't know if that was it or not.

I don't use Teflon tape, for that reason. Only tfe paste. To rule out an air issue I got a large tank of breathing air from a distributor, made sure I could get enough pressure out of the regulator, then got a flow meter, to make sure I was getting enough CFM. From there I swapped out the torches to rule out anything that was trapped in the lines of the torch. I am almost certain I have ruled out air. With that said, everything I have seen, and can actually hear the plasma stream change mid cut, that it sure seems like an Air issue.

I appreciate everyone's help. I am about at my wits end and nothing I have tried seems to help.

[srp]

I have had similar problems in the past. It drove me crazy. The best I could narrow down the problem was to the quality of the metal. My torch would behave the same as yours. With the torch acting up I changed to a different sheet and the problem went away. The metal that gave me problem was HR. Having been in this business since 1972 I have experienced many economic cycles and their effect in the metal fab business. When steel prices skyrocket all the worldwide crap hits the market. The mill clean out everything because everyone is desperate for material. The material could be a big part of your problem. I also think you are pulling a 10 ton load with a half ton pick-up. Stay sane.

[rikduk]

Just pitchin' in...If its not the plate...could it be a defective air solenoid in the plasma?

[esracerx46]

I had the same solenoid thought myself. I had tried a new torch with the first power source. I put that torch back in the box since I still had the issue. I have not tried the new torch with the new power source however.

[esracerx46]

I hate to keep shooting down everyone's suggestions. I really appreciate everything.

As far as it being a poor quality material, I had a customer the essentially dismantled one of his loaders and scrapped it for parts. He brought me a few good size chunks of 1" plate that he had blasted to get the paint off. That instance was when I first began to notice these issues.

[trucutcnc]

Try running the plasma current 10-15% higher than the tip rating. This increases the arc density and helps with kerf angles on heavier plate. Worked pretty well with our A120.

[hanix]

I haw seen something similar when power seams to fade out.
Try use ampere Clamp Meter on the input power cable when cutting if there is a difference in amps in the in one of the 3 phase that might lead to something.

http://www.youtube.com/watch?v=95vI-Xm3WHk

Hanix

[srp]

Interesting you mentioned sand blasting. As I remember the problem with older mills and the steel making process the use of silica in the smelting process added to the mix to help remove impurities caused problems. The silica imbedded in the metal might be a problem.

[cindy carlisle]

We run both TD and Hypertherm conventional plasmas. When Hypertherm came out with their new DuraMax Torch, their conventional plasma is the best on the market for little to no kerf on thicker plate We got a good cut with our TD A120 but much cleaner with the Hypertherm. Maybe you should do an upgrade to their new PM125, the BEAST!!!

[esracerx46]

I looked into the powermax 125. Unfortunately I don't have access to 440 so that's out.

I put a dc amp clamp on once before, but never on the input power leads. I put it on the ground and torch and didn't see anything. I can't remember if I could get this to issue to occur when I had the clamp or not. This is happening with more and more regularity. I'm noticing it on 1/4" plate. I don't notice it on anything lower than 100 amps, and I don't bother with the 120 amp setting because of the duty cycle.

How would I go about testing my input power with an amp clamp? Would I have to separate each wire? Aw a last resort I have a really good customer in the excavation and road building industry. I might borrow one of his big 3 phase generators and see if that clears it up. Its the only thing I haven't tried. I'm pretty certain its not material as I've gotten material from multiple suppliers, I even had this issue on some 1 inch plate from a customers old loader arms. I'm almost certain I've eliminated air, since I hooked up a tank of breathing air, and put a flow meter on. Tried a new torch. And had the power source warrantied. Only thing left is power....I think

[acourtjester]

Power monitoring equipment that can be installed the monitor both volts and amps on 3 phase power. We used the when we had a problem installing CAT and MRI systems in hospitals. I cannot remember the name of them but they are about the size of a suit case and used clip on leads for ease of installation. The power company may have one.

[esracerx46]

I appreciate everyone's help. Unfortunately I can not get this issue resolved. Occasionally I'll try something again like lightly grease the O-rings and I think I resolved the issue. But then a few hours later it rears it's ugly head.

I have a new torch that I tried once before. This time I installed it properly and tried to cut some 5/16" plate and the new torch didn't help. I have eliminated power source and torch. I believe I have eliminated air by using a large breathing air tank from my distributor and the results were left unchanged.

I am left with material and power supply. Since this issue is happening over a wide range of materials from 2 different steel companies I don't think its material, although I have no way of knowing how to rule it out.

The other day I was cutting 1/2'' mild steel plate. If I got close and looked at the plasma arc I could see the arc angle change. It would be 180 degrees from the plate then kick out for a second or 2 and come back to 180...then repeat over and over on all 4 sides of a square. I had been able to hear the change in sound, but this is the first time i was able to see it.

The only other thing I know of is to borrow a large 3 phase generator from one of my customers.....Unless anyone knows of a tech support rep, or a plasma help service in the Chicago area.

[hanix]

Sir haw you tried the ampere Clamp Meter ?

I did haw similar problem many years ago I saw difference in amps in the input power cable.
The power company didn't believe me it was like talking to wall then one morning after weekend there was no power in the house the problem was that one phase burnt in the electric case in the street that weekend 2 motors connect to air compressor burnt in the house.

After the power company repaired the connection box I newer saw this problem again and I hope newer will it was driving me crazy.

Hanix

[esracerx46]

Sir haw you tried the ampere Clamp Meter ?

I did haw similar problem many years ago I saw difference in amps in the input power cable.
The power company didn't believe me it was like talking to wall then one morning after weekend there was no power in the house the problem was that one phase burnt in the electric case in the street that weekend 2 motors connect to air compressor burnt in the house.

After the power company repaired the connection box I newer saw this problem again and I hope newer will it was driving me crazy.

Hanix

I tried using a DC amp clamp on the torch and ground cable once before. I borrowed it from a buddy so I only had it for a day or so. I don't recall seeing any noticeable fluctuations. If I put a amp clamp on the input power, I would need to test for AC correct? Also, what would I be looking for as far as amperage? I suppose any fluctuation would be cause for concern, but how much of a fluctuation would I be looking for? I have called the power company once before. Told them what was going on. He ran some "tests" and said everything was ok. Im assuming all he did was test the line voltage and split. Also, it was tested without the powersource running so I think that was an exercise in futility.

[Oldsarge]

Have you tried running your air pressure about 5-10 psi above what is recommended? Almost sounds like you're not clearing the kerf.... Just a thought.....

Oldsarge

[esracerx46]

Tried increasing the PSI, and also slightly decreasing. I've put a flow meter on the plasma to make sure I didnt see any fluctuations in air that might not show up on the regulator. Thinking that CFM and PSI arent the same thing, but I was constantly above whatever was required (off the top of my head I believe it was 6.7 cfm). Settings wise, nothing changed. All settings were known to be good at one time. Cut for a year or so before any issue arose. The issue first presented itself at the start of winter 2 years ago. Then went away come spring. They showed up again at the start of last winter, and never went away. That had me thinking temperature could be a factor. And since our shop is 60 degrees in winter that perhaps whatever is going on outside could be influenced by weather.

I could be totally wrong, but I thought Ive tried everything else. I know a few of you think it could be material related. I haven't seen any evidence of possible magnetism other than poor cuts. But I think by having this issue on multiple thickness metals and countless plates from 3 different suppliers that I might be able to eliminate that. Also, the 1 inch plate that has given me fits was cut to size by what looks like a high precision plasma. Is not torch cut.