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What air compressor CFM and reservoir size needed to run a 50 amp plasma cutter

Susquatch

Ultra Member
Administrator
Moderator
Premium Member
What specifically do I buy that would fit via 1/4 NPT quick disconnects between my airline and the plasma cutter? The combination regulator/psi gage/flow meters I have seen have Argon gas fillings versus NPT threads that can accept male or female QD fittings. (I am very new to this gas flow hardware stuff!)

Jim G

Well if it was me, I'd grossly oversize it to avoid letting the gauge affect the results. So I'd prolly make a Male & Female OBoss Hydraulic Coupling that I could separate to insert the flow meter. I say make, even though they are cheap to buy, because I'd want to integrate the coupling into the flow meter too. I'm also a fan of OBoss fittings. They are WAAAAY better than pipe thread and JIC in my opinion.
 

JimGnitecki

Active Member
With Amazon's help, I contacted BestArc, the seller for the model I have, and asked what air pressure is allowable to feed into the machine (as opposed to what psi is set INTERNAL to the machine. Here is the conversation I had with them:

BESTARC

18-Feb-2023 6:37 AM

User manual says to set psi on machine's INTERNAL regulator to no more than 75 psi. I undertsand why: setting it higher could "blow off" internal air lines. But, if I have an EXTERNAL air line coming to the machine's male 1/4 NPT fitting, can I set THAT regulator to a HIGHER air line-pressure psi to ensure that the machine gets sufficient psi and cfm? Or, would that still be a problem?


19-Feb-2023 6:31 PM

The external pressure should not exceed 150PSI. The interior pressure of the machine is determined by the front regulator. So as long as the interior pressure doesn't exceed 75psi is fine

So, I can feed up to 150 psi to the inout air fitting on the back of the machine. :)

Since the "air" is Nitrogen coming from a cylinder of high pressure and plenty of cubic feet, that should help ensure that the machine will never be starved for either air PSI or CFM.

I now also have in hand an extra regulator plus all the fittings to place it inline between the 25' 3/8" air hose and the plasma cutter, plus the Loctite 565 sealant to make all the joints airtight. I'll get that all installed within the next few days and do some more testing. (Right now, I have other priorities that I need to take care of first).

Jim G
 

CWret

Ultra Member
Premium Member
I used my cutter (Hypertherm XP45) yesterday and it occurred to me that this thread mostly talks about sizing a compressor (CFM and psi) but not much about plasma cutting.
So I'll add a couple of plasma-cutting basics:

- What gas to use:
Most home hobby guys will use compressor-supplied air. It's the cheapest solution. There are 3 compressed gases commonly used. Oxygen is the fastest and gives the best quality cut for steel. Nitrogen (like @JimGnitecki's setup) is versatile and works well for steel, stainless and aluminum. Argon/hydrogen mix is the hottest and works well for stainless and aluminum as well as for very thick materials (it is also the most expensive). Here is some more gas selection info:

- Why bother with a water table:
Plasma cutting is a very dirty business. The extremely fine dust is toxic and covers everything in the shop - much worse than spray paint. A water table greatly helps to control the dust. It also helps reduce heat in the pieces being cut (the liquid splashes up) which reduces warpage (especially in thin metals). Plasma tables do not have to be big or expensive and can still be very effective. I made my own from a 45 gallon oil drum - I copied the one that is available as a kit from 911 Motorsports (link below). I previously posted a picture and description of my table: see post 66 April 18, 22 "Planning a manufacturing class for coworkers"

- Water additives for water table:
There are lots of options here - some are just home remedies but be careful some additives can actually make the toxic fumes worse!! I use Sterling Cool. I think it is likely the best product available for a cutter. From Pete Fedorko 519 476 0459 at

- Toxic fumes:
Yes, and they are nasty. Cut outside or use a water table PLUS wear a dust mask! I use a 3M mask that is compact and fits under my face shield or welding hood. Highly recommended when plasma cutting, welding, grinding, etc. Pay the extra $10 for the model that has the quick latch.
 

CWret

Ultra Member
Premium Member
Forgot to add - I also got some cutting stencils from 911 Powersports. They were a bit expensive (50US$ per set) but make cutting square or round holes a snap. Mine are visible (if you look closely) in the post I mentioned above. They are hanging on the wall behind the press.
 

JimGnitecki

Active Member
I have been super busy, but got a chance in the past couple of days to make some progress on both my TIG welding and my plasma cutting testing.

I had previously put together a 25 foot 3/8 inch air hose with quick disconnects to connect my 300 cu ft Nitrogen cylinder to my BestArc lunchbox size plasma cutter. Then I put together a pressure gauge / regulator "module" that can be inserted between the air hose and the BestArc:

PSI gage with adaptors - 1.jpeg

I used Loctite 565 to seal all the joints, and soapy water bubble testing produced no bubbles!

This Nitorrgen + airline + psi regulator setup enables me to get 125 psi to the input of the BestArc, but to then reduce the psi INSIDE the BestArc down to 70 psi or a lower pressure, so that the inside air conncctions in the BestArc don't get overpressured.

So, now I have very controllable psi into the BesArc.

I also bought some 1/8" thick aluminum, as I had previously had only 3/16" aluminum to use in my testing, and I am veyr glad I got the 1/8".

I have now found that even with well controlled Nitrogen pressure, with basically unlimited CFM available, the BestArc still does a marginal job of cutting 3/16" aluminum, even when I crank the internal Nitrogen psi to 70 and the amps to 45 (I have only a 50 amp supply to my garage workshop, and need a bit of that for lighting).

All the plasma cutter experts tell us that for any given plasma cutter capacity, the capability to cut aluminum versus steel is only about 2/3 of the capability to cut steel. The little BestArc is rated to cut up to 1/2" steel, BUT I think that may be a stretch for this little guy. If it could really do that well, it should be able to cut maybe 2/3 x 1/2" = 1/3" = .333". But, I have found that while it will cut the 3/16" = .19" thick aluminum, it ain't pretty at all.

The little guy does much better on 1/8" aluminum when I use 70 psi and 43 amps:

Plasma cut one-eighth alum 1 - 1.jpeg

Note that the angle of the cut marks is just about perfect, the slag on top is minimal, and the slag on the bottom is relatively sparse and easily ground or sanded off.

And curved cuts are good too:

Plasma cut one-eighth alum 2 curved - 1.jpeg

Notice that the top of the cut is pretty much slag-free, and the bottom is pretty minimized too.

The angle of the cut lines is not as good as for the straight cut, but that was me, not the machine, as I did not regulate my speed of movement as well on the curved cut.

Both were done very quickly too, and therefore used up far less of the Nitrogen than the amount of air I used when trying to do this with my undersized air compressor. I experimented by cutting the afterflow of the Nitrogen down to just 6 seconds, without any adverse effect. I figured on there short (2") cuts, the cutting head would not get very hot and the shorter afterflow should be fine. So far so good.

Since the majority of my anticipated plasma cutting will be on 1/16 to 1/8" thick aluminum or stainless steel, this setup should work for me. I would have liked for 3/16" aluminum cutting to be better than it appears to be right now with this machine, but it WILL make those cuts too, just not as cleanly.

That Loctite 565 really seems to work on keeping the air (actually Nitrogen) lines from leaking. I tested my entire Nitrogen feed system from cylinder to that final psi regulator / gauge just before the QD that connects to the BestArc, by leaving the cylinder valve closed and the entire air line hose assembly regulated to 125 psi. 5 hours later there had been ZERO pressure drop.

It remains to be seen how much Nitrogen I will actually use with this setup and my rather low plasma cutting needs, but I will report in the future my actual experiences with that.

Jim G
 

Bofobo

M,Mizera(BOFOBO)
Lots of replies here and I am late to the discussion, I don’t have time to read them all but I see someone suggested multiple compressors, I have a dual voltage 110-220 fast cut 30? plasma cutter from Kms, 1 portercable pancake style and 2 dewalt single tank flat style compressors. I run the compressors in different rooms and put the desiccant dryer on the inlet fed by a airline splitter so all available pressure is not restrained by line lag (how pressure loss moves through a tube) from the 3 source lines. Only 2 compressors are really needed for smaller material, one compressor runs constant (it’s faulty pressure switch anyway from years as a roofing compressor) and one just picks up every so often. If I remember correctly I was trying to reach 7cfm with compressors under 3cfm.
 

JimGnitecki

Active Member
Lots of replies here and I am late to the discussion, I don’t have time to read them all but I see someone suggested multiple compressors, I have a dual voltage 110-220 fast cut 30? plasma cutter from Kms, 1 portercable pancake style and 2 dewalt single tank flat style compressors. I run the compressors in different rooms and put the desiccant dryer on the inlet fed by a airline splitter so all available pressure is not restrained by line lag (how pressure loss moves through a tube) from the 3 source lines. Only 2 compressors are really needed for smaller material, one compressor runs constant (it’s faulty pressure switch anyway from years as a roofing compressor) and one just picks up every so often. If I remember correctly I was trying to reach 7cfm with compressors under 3cfm.
Wow, that's a costly and very noisy solution! My ONLY tool beyond the plasma cutter that requires air is a finishing nail stapler, and my pancake compressor is more than adequate for that. I simply cannot justify the cost and noise of a big compressor (or multiple smaller ones) to feed just ONE device (the plasma cutter) that is used only occasionally. The 300 cu ft Nitrogen tank makes more sense, to me, for my specific situation.

Jim G
 

Ironman

Ultra Member
I have a 4x8 CNC table and a 80 amp Hypertherm. I feed it with a 18cfm compressor and it makes the compressor work, it does shut off, but I reckon it eats about 8-10 cfm, depending on the tip. I noted a comment earlier that you could feed at 150 psi. My compressor shuts off at 160 psi and I have fed that to the Hyper and it holds the air solenoid valve open sometimes at that pressure and the cutting air can't shut off. I put a regulator in line and knocked it down to 100 and the machine is happy.
I'll second the comments on dust. I use a 1 hp van-axial fan to downdraft the table, and I use cardboard to cover any of the grate not in use. Even so, if anything is ever feeding out into the shop, you will have a dry mouth and a funny taste in seconds. That dust is nasty.
Nitrogen is an excellent choice and gives great portability for a seldom used machine.
 

JimGnitecki

Active Member
The portability is an interesting point. To me, it does not matter. I have the nitrogen cylinder chained to a wall and a 25 foot 3/8" air hose to place the plasma cutter anywhere in my workshop. But, yes, the Nitrogen is easier to transport than a big compressor to get into and out of the back of a pickup truck for offsite work.

Jim G
 
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