Cutting 3/4" plate help

[grindergary]

I have been cutting 3/4" plate with a PM 85 and 85 Amp consumables. When I pierce, I am getting too much slag build up and the torch shield gets covered with slag. I have tried with pierce height at .24 then .28 and same problem.
Air is clean and dry. changed all filters and all new consumables. Air is on automatic on plasma. I went to a little longer delay to see if that would help.

Does anyone use the PM 105 for 3/4 and do you have any problems?

The funny part is I can cut 3/8 and 1/2 inch with 85 or 65 amp and the pierce is almost instant.

Any ideas?

Thank you in advance,

Gary

[beefy]

I've had exactly the same problem with the 85 amp nozzles in the past. The little air holes of the shield would get slag blockages on the first pierce. Big mound of slag on the plate that the torch would just about touch when it came down to cut height. It would be great to have a custom lead in that could ride over the slag at pierce height before coming down to cut height.

I even started looking into doing all pierce holes first with old nozzles, cleaning the slag off, then changing to a good nozzle and doing the cuts with an "edge start" on the pierced holes. I got close to making it all work then other duties pulled me away.

I'd love to know how the top end machines do piercing on thick plate. I've heard they do all sorts of movements during the pierce to avoid this slag problem.

I see you also had a problem some time ago with piercing 5/8 plate with the 65 amp nozzles. Did that one turn out to be air pressure http://www.plasmaspider.com/viewtopic.p ... 573#p57573

Just out of curiosity have you ever had that cut lean problem too, as though the torch was mounted at an angle. Just trying to see if our systems (same torch) have common problems.

Keith.

[grindergary]

The 5/8" problem has gotten better to a point. I put new air filters and seemed to help but every once in a while it will plug up the shield with slag. I cut over 320 pierces on 5/8 plates 2 weeks ago. Now at 300 pierces, I change the consumables and carry on. But, every once in awhile it does it again. I increased my pierce height as per JIm Colt and that helped too.

I found that on the pierce, if the slag gets on the shield, the THC reads wrong and I have seen the head drive into the plate. Broke the sleeve that holds the head on Friday. I know it is probably my fault(as the wife keeps telling me )

I understand in sheetcam there is a wiggle pierce and something else. That works but not foolproof.

The air pressure on the 5/8 is not the problem. The PM 85 and 105 are auto set. I have taken the torch apart and cleaned everything.

I really would like to try CandCNC new post processor set up they have with sheetcam but not ready to change my machine with all the work I bid on. Besides, waiting to see if they make a video on how to set up and use it. Just need to set up and learn it I guess.

Yes, I have had that problem too. Even with THC control, I find I get leaning cuts once in a while. As soon as it happened, I checked the head for square and it was good.

It is frustrating when you can blow thru 1/2" plate like butter then have so much trouble with thicker material. I have turned away work so I don't have to worry about the heavy plate. 95% of what I cut is 3/8 and 1/2" but would be nice to get some of the other stuff.

So, clean dry air, new consumables and set machine to proper amperage. Post processor set to book specs, except for pierce height, still cant get it to pierce like it should.

Gary

[beefy]

Yeah these problems can be like ghosts in the night.

That lean in the cuts problem. I've had it bad since my Duramax torch was brand new (65 & 85 nozzles, 45 cut nice) but I've never really delved into it because I haven't done much thick stuff and what I did do was just for my own use. So much other stuff to see to. Sooner or later I'll have to find out what is causing it. There's no way I can make money on thicker steel until I get it sorted.

The ultimate measure of torch air is flow, not pressure. We could have plenty pressure at the inlet to our machine but without a flow meter we don't know if we are getting the correct flow, we just assume / hope we are. The Hypertherm manual gives a specification in Standard Cubic Feet per Minute, but I'm not 100% sure what that means, or how I'd implement measuring it in our systems.

I recently came across a thread in another forum

http://www.cnczone.com/forums/hyperther ... blems.html

and the guy had the Duramax torch (Powermax 85). He was yet another one plagued with this lean problem and he checked absolutely everything, changed all consumeables, and the problem remained. Plenty air pressure into his machine. Running out of things to look for it was suggested he may not have proper air flow (i.e. internal restriction) at the torch despite having plenty inlet pressure.

I'm just wondering if there's any connection between the piercing problem and the cut lean problem. The general feedback with the Duramax torches is very positive and I've seen great cuts on 1" steel (he had 135 psi into his machine AFTER the filters).

I'm just thinking out loud Gary but could a lack of air FLOW be why the torch leaves a big mound of slag, there's just not enough air velocity to blast it out of the road.

Keith.

[jimcolt]

320 pierces on 5/8" is pretty good for any air plasma system. There should be no reason why you cannot get the same on 3/4" steel with the 85 amp process as well. The Hypertherm maximum pierce thickness spec is based on the ability to achieve 300 starts....that is true with all of our systems.

There are some things that will shorten nozzle and shield life:

- If you are doing a lot of piercing with no time between them.....such as dozens of small holes piercing one after the other....the shield and nozzle do not benefit from the post flow cooling. When the shield gets very hot, molten blowback can easily stick to it. Once there is steel stuck to the shield then more steel sticks to the steel....and life will be short.

-Pierce height, and I cannot overstress, is critical. One pierce too close and the nozzle and shield will be damaged, this is more critical as the material gets thicker. A damaged sheild or nozzle will cause varying cut edge angularity on all subsequent cuts.

-Airflow in a plasma torch is determined by the cut pressure (set by the air pressure control system in the plasma power supply) in conjuction with the consumables. The orifices in the swirl ring, the passages in the retaining cap, and the nozzle orifice as well as the shield orifice and pressure equalizing bleed holes all contribute to ensuring the correct air flow at the nozzle and at the shield. If there are any restrictions (or leaks) between the power supply and the torch head, then cut quality and torch cooling will be affected. Further, if any of the above mentions components (swirlring, retaining cap, nozzle, shield) are damaged or manufactured to incorrect specs, cut quality and torch cooling are affected.

- Of course, like with anything, running at the edge of the specs (piercing 3/4" with a plasma rated to pierce a maximum of 3/4") will make the process very touchy. If you are doing high volume production and you want a process that is not running on the ragged edge....I always suggest specifying a process that runs in the middle of its specified range. In a 3 shift a day, high volume manuafcturing operating that cut 3/4" material most of the time....we would recommend nothing less than a 200 amp, liquid coooled plasma cutting system. 85 amps will pierce and cut its max of 3/4" (if everything is close to perfect), 200 amps will do it with consumable life in the 1200 to 2000 pierce range, at faster speeds and with better cut quality, unfortunately at a much higher purchase price.

-If you are 100% sure that you are doing everything correctly, air pressure and purity are correct, and you cannot pierce at Hypertherm's published specs (which I stand behind 100%.....I have a Powermax85 on my home shop machine), then perhaps there is an issue with the torch, torch leads, or the air system in your power supply.

Jim Colt Hypertherm

[grindergary]

Hey Jim.
Thanks for your response.

What I was looking for was if the 105 would work better on the 3/4" plate. I would love to throw a 200 amp machine on here but I don't think it will work on my table. Sure, the price is high, but the cut is better. I have the 105 and am going to set up for it as soon as time permits.

With all machines, there is bound to be things happen. I did 320 pierces on one sheet. That was great! The problem is I put new consumables (all this time) and on the 3rd pierce, it blew slag back into shield. Cleaned easy but won't take long that way to ruin the shield. Cut a dozen more parts then started to blowback again.

As for the air blowing after cut, there is 8 seconds from stop to start of torch.

I think the 85 works good for what i am doing but I am going to try the 105 when i can for the heavy plate.

Thanks for all your help all the time,

Gary

[beefy]

Hi Jim,

does Hypertherm have any suggestions for how a user can confirm correct airflow. To be honest my head was always thinking of restrictions but like you said, internal leaks can dump the air and hence you don't get all the airflow to the torch.

This sort of suggests to me that the only accurate way of checking flow at the torch itself would be to measure what's coming out the end, then of course it's at atmospheric pressure.

Cheers,

Keith.

[jimcolt]

Yes, 105 amps will work better on 3/4" plate as compared to 85 amps, no doubt in my mind....125 amps will work even better, and 200 amps even better! That is why we have so many different power levels, as well as a line of air plasma systems for hand held and lower duty cycle, lower production cutting, as well as a line of industrial, 100% duty cycle, three shift a day plasma cutting systems. If you spend more time cutting thick material, you often need more power.

Jim Colt

Hey Jim.
Thanks for your response.

What I was looking for was if the 105 would work better on the 3/4" plate. I would love to throw a 200 amp machine on here but I don't think it will work on my table. Sure, the price is high, but the cut is better. I have the 105 and am going to set up for it as soon as time permits.

With all machines, there is bound to be things happen. I did 320 pierces on one sheet. That was great! The problem is I put new consumables (all this time) and on the 3rd pierce, it blew slag back into shield. Cleaned easy but won't take long that way to ruin the shield. Cut a dozen more parts then started to blowback again.

As for the air blowing after cut, there is 8 seconds from stop to start of torch.

I think the 85 works good for what i am doing but I am going to try the 105 when i can for the heavy plate.

Thanks for all your help all the time,

Gary

[jimcolt]

Keith, I am not aware of any method of measuring the airflow of our torches. Our tech service department may have a method....you could check with them....although I think I would have known about it if they did! A tech would swap torches with a known good one....if it works better then the torch was the issue. I realize that is not doable without a spare torch.

Jim Colt

Hi Jim,

does Hypertherm have any suggestions for how a user can confirm correct airflow. To be honest my head was always thinking of restrictions but like you said, internal leaks can dump the air and hence you don't get all the airflow to the torch.

This sort of suggests to me that the only accurate way of checking flow at the torch itself would be to measure what's coming out the end, then of course it's at atmospheric pressure.

Cheers,

Keith.

[beefy]

Thanks very much Jim.

Keith.

[fergy]

yeah I have a 105 on a torchmate table
works well pet pierces do stuff up the holder at times
I also have oxy/lpg on the same table and if I need a perfect cut I will oxy cut parts
3/4 is about the size where it seems to be better to oxy cut
but I don't get a lot of time to stuff with heights etc
so with perseverance you would get it sorted with a 105 I would think