FOLLOWING the Lincoln Electricguide to buying a plasma cutter, the company has outlined some tricks-of-the-trade to help beginners optimise their plasma cutting techniques.
Set-up procedures form the foundation of the cut. Before starting, users should ensure their compressed air supply is clean, without water or oil. Contaminated air can cause consumables to wear quickly or result in black burn marks on the plate.
Air pressure should be set to the correct level. This can be checked by looking at the gauges on the unit. The nozzle and electrodes should also be positioned correctly.
When cutting with plasma equipment, certain safety practices should be used. The cutting process will generate molten metal, necessitating the use of long sleeves and gloves. Eye protection such as dark goggles or a welding shield with a darkness shade of 7 to 9 is needed to protect eyes from the cutting arc.
When piercing the work with the torch, it is recommended to approach the metal at an angle of 60 degrees from horizontal and 30 degrees from vertical. The torch can then be rotated to a vertical position. If the metal is pierced at 90 degrees, molten metal will be block back into the torch. But using an angle, the metal is blown away.
The nozzle should not touch the work piece if using current levels of 45 amps or more, as the cutting will double arc through the nozzle, reducing the nozzle life. At a beginner level, it is also recommended to use a drag cup over the nozzle so the torch can rest on the work piece and dragged along to facilitate a consistent cut.
The speed of the cut is also important. When at the right cutting speed, the molten metal spray should blow out the bottom of the plate at an angle. If the speed is too slow, molten metal will accumulate on the bottom edge of the cut. If the speed is too fast, the molten metal will be trapped on the top surface. Both instances of incorrect speeds ill result in a low-quality cut.
The current should be set to the maximum when beginning the cut, then turned down as needed. More power is recommended when doing precision cutting or when a small kerf is needed.
Pilot arc wears down consumables rapidly, so the amount of time spent in the pilot arc mode should be kept to a minimum. The plasma torch should be positioned by the edge of the work before starting the arc so cutting is instantaneous.
Once the distance from the nozzle to the work piece has been established, it should be kept consistent. Moving the torch up and down will hinder cutting. The cut should also travel in the direction suiting the application. When making a circular cut where the round piece is prioritised, the torch should move clockwise. If prioritising the piece from which the circle was cut, move the torch counter-clockwise.
When working on thicker material, the torch should be rotated slightly. The torch orientation should be increased to a push rather than drag when cutting through the last section of the material. This will cut through the bottom first and avoid the bottom corner usually left at the end of thick plate.

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