17
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
Hold the torch vertical at the edge of the
work piece and place the stand off guide 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.
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Hand torch cutting technique
When cutting make sure that sparks are
exiting from the bottom of the work piece.
If sparks are spraying up from the work
piece, you are moving the torch too fast, or
you don't have enough amps set.
Hold the torch vertical and watch the arc as
it cuts along the line.
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Starting a cut
AT1000
AT50505
