Compressed Air for Plasma and Laser Cutting – Air Compressor Manufacturers

Plasma cutters and laser cutters often sit side by side in shops, but gas source configuration is completely different. Plenty of people learned this the hard way.

Plasma Cutting Air

Plasma

Arc Cutting Process

Air Supply

Compressed Air System

Plasma cutting uses compressed air as working gas, electric arc heats and ionizes it to melt through metal. Pressure 5 to 7 bar, this parameter is clearly written in manuals, not easy to get wrong.

5-7bar

Plasma Pressure

400+

L/min High Power

12-20bar

Laser Pressure

0.01μm

Final Filtration

Air consumption is easy to underestimate though. Small machines use one to two hundred liters per minute, get on a cutting table and it's different, high power models go 400-500 liters and up. Compressor selected too small, pressure drops while cutting, plasma arc starts spreading, cut edge gets rough, heavy dross. Many people's first reaction is to change the nozzle, but actually the problem is the air source.

Consumable Life

Electrodes and nozzles are consumables, normally one electrode can strike 300-400 arcs. But some shops need to change at 200, air quality is a big factor here. Oil in compressed air gets into the plasma arc, hafnium insert surface forms carbonized deposits, erosion accelerates. Water content means faster oxidation too, life takes a hit.

Judgment method isn't complicated, take out the electrode and look at that pit in the hafnium insert. Normal wear should be a fairly regular circle. If pit shape is crooked, edges have cracks, or pit bottom is blackened, most likely gas source has problems.

Hypertherm manual recommends ISO 8573 Class 1:4:1, this standard is basically achievable with refrigerated dryer plus three-stage filtration. Many shops don't meet it not because equipment is inadequate, but because filter elements are overdue for changing.

Laser Cutting Is Completely Different Story

Laser Technology

High Precision Cutting Requirements

Laser cutting uses assist gas to blow slag, protect lens, can use oxygen, nitrogen, or compressed air.

First pressure. Laser cutting needs 12 to 20 bar, ordinary shop air source at 7-8 bar isn't even close. Laser cut kerf is narrow, slag needs high pressure to blow out.

How to solve? Can use high pressure screw machine, Atlas Copco has models specifically for laser cutting. Can also add booster to boost ordinary air source pressure up, lower initial investment. Boosters have seals inside, wear over time producing debris, filters downstream need changing more often.

Cleanliness is laser cutting's real headache.

Cutting head has focusing lens inside, assist gas blows past it. Oil mist lands on it, laser's power density that high, lens coating burns instantly. TRUMPF original focusing lens assembly pricing is scary, domestic alternatives still run several hundred bucks.

Some shops change protective lens every few days on laser cutters, thinking it's normal consumption. Actually not necessarily, if gas source cleanliness has problems you change more than others. Class 1:2:1 is bottom line, Class 1:1:1 is more stable. Three-stage filtration may not be enough, final stage needs 0.01 micron, plus activated carbon adsorber.

Piping layout also matters. Filters installed in compressor room, piping runs dozens of meters over, water and crud accumulated in pipes still gets blown into equipment. Final stage filter installed close to cutting machine is safer, some shops just add another stage right before the inlet.

Dryer Selection

Refrigerated

+3°C Dew Point

Adsorption

-40°C Dew Point

Filtration

Multi-Stage Setup

Refrigerated dryer output has dew point around 3°C, good enough for plasma cutting, laser cutting depends. Adsorption dryers can do minus 40°C, go with that for high requirements.

One trap to watch: rated dew point and actual dew point often don't match. Refrigerated dryer performance is affected by ambient temperature, summer performance will be worse. Winter when shop temperature is low, 3°C dew point air might condense water in cold pipes. Northern winters with unheated shops, temperature can go below zero, refrigerated dryer becomes questionable.

Cutting shop has AC, comfortable at 20-something degrees, but compressed air piping routed outside and back in. Winter pipe temperature is only a few degrees, water condenses in that section of pipe. Fixed by routing inside or insulating the piping.

Pressure Stability

Pressure fluctuation during cutting shows in the cut. Plasma arc will wobble with it, laser cutting slag blown unevenly, cut quality varies front to back.

Air receiver can buffer some fluctuation, size based on air consumption, enough to hold over 30 seconds.

Regulator precision actually matters more. Ordinary regulators fluctuate two or three points, that's normal. High requirements need precision regulators, fluctuation can be held to plus/minus 0.05 bar.

Booster-fed situations need more attention to pressure stability, booster outlet pressure fluctuation is inherently bigger than regular compressor. Best to have dedicated receiver after booster, receiver can be sized larger, then precision regulator, isolated from other shop use points. Some shops skip the isolation to save trouble, result is other equipment uses air and laser cutter pressure wobbles, cut quality becomes inconsistent.