How Does Plasma Cutting Work?
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A Small Box
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Plasma cutters have come a long way in the development of cutting metal with an electrical arc, the plasma, and compressed air. When first introduced onto the market, the plasma cutter unit was the size of a small refrigerator. Now these modern electrical packages are as small as a piece of carry-on luggage or four, full sized loaves of bread stacked in a 2-by-2 fashion. Some units even have an onboard air compressor that makes the accurate metal cutter extremely portable, as it can be plugged into any typical home wall outlet.
Low Voltage, High Current
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The plasma cutter utilizes an electrical transformer and internal circuitry to transform the outlets power of 120 volts alternating current (VAC) with a current draw of 15 amperes, into a low voltage high current cutting stream. The typical voltage range of the plasma cutter can be in the area of 20 to 50 volts. The current on the other hand can have a high output of up to 100 amperes. It is this high current that creates the identifiable blue and white cutting stream of electrical plasma. Electricity is carried on the outside of all electrical wires. It is the free electrons of copper, the most common wire to conduct electricity, that carries or moves the power from one point to another. The plasma cutter with its unique circuitry concentrates this electron flow into a stream of cutting power. The electrons form a plasma-like substance that can be seen when the trigger is pulled on the cutting torch handle. It is this intense plasma that heats and melts the metal into a small diameter puddle.
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Compressed Air, the Final Force
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Once the molten puddle is made, another force is needed to "push" the puddle through the other side of the material being cut. Compressed air, in the range of 100 pounds per square inch (PSI), is conducted through the torch handle and released when the trigger is pulled. This plasma stream is now complete and creates the small diameter, but fine line for cutting metal. Generally the plasma stream is so intense that the torch handle can be moved along the surface of the material in speeds of 100 inches or more per minute. Comparing that to other types of cutting torches, which can only achieve a maximum speed of 30 inches per minute, makes the plasma cutter a high-speed cutting apparatus.
The Angle of Cut
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One minor draw back or physical characteristic of the plasma cutter is the angle of the final cut in relation to the material. The plasma arc will cut a 6 to 7 degree angle on the vertical face of the material. Thin metal stock will not have an appreciable face angle that has to be dealt with in as much with thicker material. Metal work pieces a ¼ inch or greater may have to be dressed with an electric grinder in order to have a true perpendicular angle in relation to the horizontal surface.
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