Unimig KUPJRRW45, Operating Manual

13

Operating Procedure & Techniques 
for PLASMA Cutting

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Air pressure and volume

Air pressure, flow rate and air quality are critical to quality plasma cutting and consumable life span. 
The required air pressure and volume can vary from model to model and the manufacturer will provide the specs.  
The volume capacity of your compressor is important, if you have a small compressor with exactly the same l/min rating as the 
plasma, then the compressor will run continuously when you are plasma cutting, a compressor with a l/min rating slightly higher 
than the plasma would be more adequate.  If you are doing a lot of cutting, cutting thick plate (same air consumption but slower cut 
speeds = longer cut time) then choose a compressor at 1.5 to 2 times the plasma system requirement.

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Air quality

Good air quality is essential to quality plasma cutting and consumable life span.
Compressors take in air at atmospheric pressure and increase the pressure and store it in a tank. Humidity in the air is condensed 
in the tank and in the airlines producing water, more so in humid environments.  Moisture that forms in air lines has a tendency 
to condense into larger drops when the air pressure decreases as it is entering the plasma torch. When these droplets enter into 
the high temperatures (as much as 11,000°C) in the plenum of the torch, they immediately break down into oxygen and hydrogen, 
which alters the normal chemical content of air in the torch. These elements will then dramatically change the plasma arc which 
causes the torch consumable parts to wear very quickly, alters the shape of the nozzle orifice, dramatically affecting cut quality in 
terms of edge squareness, dross formation, and edge smoothness. Minimising the moisture in the air supply is absolutely critical to 
quality plasma cuts and longevity of consumable parts. As a minimum be sure to drain the receiver (tank) on the air compressor at 
least daily.   
Most air plasma systems from reputable manufacturers have an on board particulate filter and or a coalescing filter with an auto 
drain that will remove some moisture from the air supply. For home workshop and light industrial users the on board air filter is 
adequate. Most situations however will require additional filtration to prevent moisture from affecting the quality of the plasma cutter  
and in most cases it is recommended to install a sub micronic particulate filter that is designed to trap water through absorption. 
This style of filter  has a replaceable filter cartridge that absorbs water and must be changed after it is near saturation, it should be 
installed close as possible to the air intake of the plasma cutter.

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Technique Tips

•  It is easier to pull the torch through the cut than to push it.
•  To cut thin material reduce the amperage until you get the best quality cut. 
•  Use the correct size tip orifice for the amperage being used. 
•  For Straight cuts use a straight edge or cutting buggy as a guide. For circles, use a template or circle cutting attachment. 
•  Check that the front end consumable parts of the plasma cutting torch are in good condition.

Sub Micronic Filter 

Filter Element

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Starting a cut

Hold the torch vertical at the edge of the 
work piece and place the cutting tip on the 
workpeice.

Pull the trigger to start the arc.
Start cutting on the edge until the arc has 
cut completely through.

Then, proceed with the cut.