plasma cutting psi ?

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Is there a chart or rule of thub about how much air pressure is required to cut a given thickness of material. Most manuals say nothing more than 70-150 psi required ... is it just up the user to figure out how much air it takes to make the cut ?I was cutting a bit with one last night and was surpised to the see the slag filling up the bottom of the cut just behind where I was cutting. Although that could be a speed of travel issue more than an air pressure issue...
Reply:Thats a speed of cut issue. I set the pressure on my Spectrum 375 at 60 PSI with the air flowing. I change the amps, and feed speed to match the material. I use a "Stand off" for 90% of my work.
Reply:thanks jim .. I figured I was going to slow ... I kept staring at the cut in amazement that I was pulling the trigger and the metal was just blowing away. It was the first time I'd used a plasma cutter ... nifty device.
Reply:The Spectrum 375 wants you to give it 80-100 psi from your compressor and then to adjust its internal regulator to a fixed 60 psi, no matter what the cut is.
Reply:Mine(hypertherm 100) just wants a constant 70 psi. It needs air volume or it cuts out. I had to get a larger air compressor,so it would keep up with the cut. It works good now. Usually when you get the speed right for the thickness of the steel there is almost no slag. Too fast seems to have more slag and too slow seems to leave a wider kerf and not as smooth. DavidDavid
Reply:Mac,Like your new avatar!hank
Reply:My Spectrum 2050 says to run it at 70 PSI also, I run it around 75 usually I like the results.  I get 125 to the machine.  Most Plasmas I've seen have internal regs, and they are usually set between 60 and 80 psi.  Echo it is not called slag with a plasma or laser it is called dross.  Morpheus, general rule dross should be able to be removed with a chipping hammer with ease.  If it can't; review you settings, travel speed (likely too slow) and look at you tip and electrode.  They maybe significantly eroded.Also don't drag your torch unless you have a drag tip on it.What unit did you buy???Ron ShopFloorTalk Millermatic 350P, M-25, M-40 gunsDynasty 300DX, Coolmate 3, Crafter CS-310 TorchTrailblazer 302, 12RC, WC-2430A spoolgunSpectrum 2050Thermal Arc Plasma Welder PS-3000/WC-100B
Reply:Originally posted by hankj Mac,Like your new avatar!hank