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Plasma cut quality.

Cyclotronguy

Stainless
Joined
Sep 21, 2005
Location
Northern California
Hand cutting 3/8" A36 using a respected 65A machine, with compressed air, fresh consumables. Inside the heat effected zone I'm seeing the classic red iron oxide deposit, The compressed air supply is fed from a refrigerated air dryer rated at 20 CFM,followed up by the ubiquitous toilet paper cartridge

Cut quality otherwise seems pretty good for a drag cut.

Is the red, residue normal or do I need to revisit my air supply quality with respect to water removal?


Cyclotronguy
 
I don't think I've ever seen a red rust on the cut face.

I doo get the slate colored scale that comes off easily (not to be confused with the slag on the bottom edge).
 
Thanks Doug

That's what I thought, this is a red smut that is down through the cut, wipes off easily enough. The gray scale that we expect from plasma / air is a bit more tenacious.

Dross is a bit heavier than I expect on the bottom, like the cut is too slow.... but if I speed up I don't get full penetration in 3/8 plate

Machine should be capable of a quality cut in 1" material at 12in / min

It's been near 100 degrees ambient and humid with the compressor running hard... thinking that the 20CFM Ingersol refrigerated air dryer is simply not keeping up with the demand.
 
Thanks Doug

That's what I thought, this is a red smut that is down through the cut, wipes off easily enough. The gray scale that we expect from plasma / air is a bit more tenacious.

Dross is a bit heavier than I expect on the bottom, like the cut is too slow.... but if I speed up I don't get full penetration in 3/8 plate

Machine should be capable of a quality cut in 1" material at 12in / min

It's been near 100 degrees ambient and humid with the compressor running hard... thinking that the 20CFM Ingersol refrigerated air dryer is simply not keeping up with the demand.

Could you try a bottle of nitrogen for a test ?
 
Yes N2 is doable, as long as the local Airgas has a bottle in house and that would behave very much like air under ideal conditions.... excellent call, thank you!

O2 and plasma are spectacular at cutting steel, that said I don't know if there was oil in the compressed air stream so am very reluctant to even consider Oxy

Kent
 
Yes N2 is doable, as long as the local Airgas has a bottle in house and that would behave very much like air under ideal conditions.... excellent call, thank you!

O2 and plasma are spectacular at cutting steel, that said I don't know if there was oil in the compressed air stream so am very reluctant to even consider Oxy

Kent

Consult the charts for your machine.

DO NOT under any circumstances connect to Ox if the machine is not specific
to run Ox.
 
Hand cutting 3/8" A36 using a respected 65A machine, with compressed air, fresh consumables. Inside the heat effected zone I'm seeing the classic red iron oxide deposit, The compressed air supply is fed from a refrigerated air dryer rated at 20 CFM,followed up by the ubiquitous toilet paper cartridge

Cut quality otherwise seems pretty good for a drag cut.

Is the red, residue normal or do I need to revisit my air supply quality with respect to water removal?


Cyclotronguy

Not sure what power source your using, but here we run all Hypertherm plasma generators, both air and high definition.
That said a 65 amp machine will pull around 7 SCFM@ 85 PSI, not sure of the size of your compressor, but your air drier at 20 SCFM certainly would be sufficient, as long as it is working well, does it ever discharge moisture?. I personally like the Motorguard filters, just keep up on them as the aluminum tends to break down internally if the filter gets too saturated and sets long term. If your compressor is not cycling during cutting then you very well could be dropping below the recommend SCFM/PSI. Although you should see that in your cut quality or a plasma generator fault warning/shut down.
Red within the cut is not all that surprising, is your A-36 clean, oil film, large amounts of scale, etc. What ever is on the outside of the plate as well as inside in the case of Russian steel, (but that's another story), becomes part of the plasma stream.
A few years back some crap steel out of Ukraine was so heavily pickled even after a good cleaning we got some odd discoloration around the outside of the cut.
Your preforming free hand plasma cutting so I would think that your not shooting for a super precision kurf quality cut.
I think I would skip on Nitrogen and most certainly NOT OX.
 
Dana,
My suggestion of getting a bottle of nitrogen was simply for a test, to see if water
in the air was the problem, as the bottle of nitrogen will be dry.

Not daily usage.
 
Yes Hypertherm 65.

I think the deal is insufficient air volume feeding air into the machine via a 1/4 inch interchange fittings (plural) and 20 ft of 3/8" hose with regulator at the supply end of the hose. No fault code showing.

No sign of any foreign material in the motorguard paper filter ever. N2 didn't improve things much.

Switched to higher flow Milton V fitting and regulator set for 100 Psi right at the machine, instead of right after the filter and cut quality went up. Yes hand cutting, with guides, but technically freehand.

Thanks guys!
 
I run my 45xp off 100' of 3/8" hose and 1/4" npt fittings, but the source pressure is 140psi.

IIRC, torch pressure is about 45psi so there's definitely a cut within the machine. Good luck.

Sent from my SM-G981V using Tapatalk
 
Yes Hypertherm 65.

I think the deal is insufficient air volume feeding air into the machine via a 1/4 inch interchange fittings (plural) and 20 ft of 3/8" hose with regulator at the supply end of the hose. No fault code showing.

No sign of any foreign material in the motorguard paper filter ever. N2 didn't improve things much.

Switched to higher flow Milton V fitting and regulator set for 100 Psi right at the machine, instead of right after the filter and cut quality went up. Yes hand cutting, with guides, but technically freehand.

Thanks guys!
20 Feet of.250 I.D hose won't be a problem for the 65, off the top of my head .250 should be good for about 13 SCFM @ 120 PSIG.
Your 65 will pull around 7 SCFM @ 85 PSIG and input pressure to the 65 is generally 85 PSIG.
Pressure drop in 20 feet of .250 will be somewhere around 18 PSIG, Sooooo even when using a .250 hose/fittings whatever with a 120 PSIG line then 13 SCFM would still be provide 105 PSIG well within the range of the 65.
The 65 it's a great machine just watch consumables, your operators manual will provide a maximum erosion depth for the electrode and check the nozzle port for out of round like a slight oval hole.
 








 
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