What air compressor CFM and reservoir size needed to run a ...

I recently got one of the lunchbox size 50 amp plasma cutters. The machine does a good job cutting on short cuts, but my current pancake air compressor is, I think, simply too small to support the plasma cutter on longer cuts or repetitive short cuts.

My current Bostitch pancake air compressor has only a 6 gallon reservoir tank and is rated for only 3.7 SCFM at 40 psi and 2.6 SCFM at 90 psi. It cuts out psi buildup at 150 psi, and cuts back in when the psi drops to 120.

The first few short cuts with the plasma cutter are fine, but then the air compressor starts up and has to KEEP running, and I can see the psi dropping on the palsma cutter's psi gauge (Glad it has one!).


The user manual for the plasma cutter has tables for cutting material that tells you the amps and psi to use, and cutting 3/16" test material apparently requires only about 25 amps and only 40 to 50 psi, but I am assuming I need more amps because the 3/16" material I am cutting is aluminum, and maybe also more psi? So, I am using 30 amps. The manual does not in the tables highlight the CFM required, but later, buried in text, it does say that 6 CFM is required! It also says to not exceed 75 psi (presumably because more psi is not needed and maybe because they don't want you blowing off internal air lines with 100 or 150 psi connected to the machine's inputs.

In addition, I need to mention that I live in a geographic area with VERY dry air (good) and at 3000 ft elevation (bad). The 3000 ft elevation apaprently degrades an air compressor's actual CFM output.

So, I THINK I need TWO things that my current air compressor does not have:

1. a CFM output of at LEAST 6 CFM at 40 to 70 psi, and maybe more because of the high altitude

2. A much larger air reservoir tank, so that the compressor is not forced to start running partway through a long cut. I am assuming that even when the air compressor is running to replenish the tank's psi, and thus also the air volume that feeds the CFM, if it is running, it is likely not sending a STEADY psi or STEADY CFM to the plasma cutter.

If any of you are knowledgeable and experienced with air compressors, what would you recommend?

Note that I know of course that I can simply overkill and get a really large air compressor, but the plasma cutter is the ONLY usage for a larger air compressor (the pancake air compressor works fine for my only 2 other uses: tire air pressures on 3 vehicles and a trailer, and feeding my finish nailer. Therefor I would feel silly buying a large costly air compressor to feed only my very inexpensive and only lightly used plasma cutter.

Also, most large capacity compressors are also oil-filled, and that necessitates maintenance, AND adds oil into the air which must then be REMOVED because it kills plasma cutter torch consumables. So, I'd like to stay away from oil!

Jim G

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STEPCRAFT CUT 50 Plasma Cutter System

Cut Settings Chart

The CUT 50 is a very capable and powerful plasma-cutting system.  When coupled with your M-Series CNC machine, you have a system that can cut up to 5/8" thick mild steel.   While this might not be the norm, it is possible with the right settings.   The following charts will give you some starting settings to use when programming your plasma jobs. 

In the charts, we will provide info on air pressure, amperage, pierce height, cut height, and feed rate (cutting speed).  
Air Pressure: This is adjusted by the black knob on top of the air pressure regulator and filter on the back of the Plasma cutter unit.  Simply turn the knob and look at the dial on the regulator until you get the correct pressure setting
Amperage: This is adjusted by turning the dial on the front of the plasma cutter unit until the amperage number is reading correctly on the front of the unit. 
Pierce Height, Cut Height, and Feed Rate: These are all settings you will make in Sheetcam in the Operations section. 

NOTES:

• These settings are rough starting positions.  Adjust your machine's settings to get the best cutting results.  You can consult our document HERE on how to obtain the best results. 

• The air pressure gauge that comes on the CUT 50 Plasma Cutter is in MPa (MegaPascals). This is a basic unit of pressure measurement in the International System of Weights and Measures.  We give you both MPa and PSI in the charts below.

• This chart might be updated from time to time as we test-cut other materials, so please bookmark this page and check back when you are setting up your plasma-cutting jobs.

MILD STEEL

AMPS AIR PRESSURE
MPa/PSI MATERIAL THICKNESS PIERCE HEIGHT/CUT HEIGHT PEIRCE DELAY
(Sec) FEED RATE (IPM) 20 .35/55 24GA 0.125"/0.06" .1 205 25 .35/55 20GA 0.125"/0.06"
.1 190 30 .35/55 16GA 0.125"/0.06"
.2 150 40 .41/60 14GA 0.125"/0.06"
.2 105 45 .41/60
12GA 0.125"/0.06"
.5 90 45 .41/60
3/16" 0.125"/0.06"
.8 60 45 .41/60
1/4" 0.19"/0.06"
.9 45 50 .45/65
3/8" 0.19"/0.06"
1 35 50 .45/65
1/2" 0.24"/0.06"
1.2 20

STAINLESS STEEL

AMPS

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AIR PRESSURE

MATERIAL THICKNESS

PIERCE HEIGHT/CUT HEIGHT

PEIRCE DELAY

FEED RATE (IPM)

20 .35/55
24GA 0.125"/0.06" .1 188 25 .35/55
20GA 0.125"/0.06"
.1 125 30 .35/55
16GA 0.125"/0.06"
.2 88 40 .41/60
14GA 0.125"/0.06"
.2 76 45 .41/60
12GA 0.125"/0.06"
.5 62 45 .41/60
3/16" 0.125"/0.06"
.8 50 45 .41/60
1/4" 0.19"/0.08"
.9 37 50 .45/65 3/8" 0.19"/0.08"
1 31 50 .45/65
1/2" 0.19"/0.08"
1.2 18

ALUMINUM

AMPS

AIR PRESSURE

MATERIAL THICKNESS

PIERCE HEIGHT/CUT HEIGHT

PEIRCE DELAY

FEED RATE (IPM)

20 .35/55
24GA 0.125"/0.06" .1 230  25 .35/55
20GA 0.125"/0.06"
.1 174 30 .35/55
16GA 0.125"/0.06"
.2 126 40 .41/60
14GA 0.125"/0.06"
.2 102 45 .41/60
12GA 0.125"/0.06"
.5 88 45 .41/60
3/16" 0.125"/0.06"
.8 72 45 .41/60
1/4" 0.19"/0.08"
.9 51 50 .45/65
3/8" 0.19"/0.08"
1 36 50 .45/65
1/2" 0.19"/0.08"
1.2 22

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