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What is a Plasma Cutter?

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  • Written By: Alison McAdams
  • Edited By: L. S. Wynn
  • Last Modified Date: 20 September 2014
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A plasma cutter is a relatively easy-to-use tool to cut steel and other electrically-conductive metals. These cutters work by using a high-voltage electrical arc and a compressed gas, usually air. An electrical arc generated by an internal electrode ionizes gas passing through a nozzle, creating a concentrated arc of plasma at the cutter's tip. The arc's contact with the working surface makes a high heat circuit which melts a section less than 1/16" (1.6mm) wide. The force of the plasma flow then literally blows out the molten area on the work piece, creating a fairly clean cut with little or no slag. The plasma arc travels through the nozzle at a speed of up to 20,000 feet per second, and at temperatures as high as 30,000 degrees Fahrenheit (16,600 Celsius)!

Light, portable plasma cutters use 110 volts with an output of around 12-35 amps. To simplify their use, these machines often feature with on-board air compressors. Larger cutters are 220 volt systems with an output between 50 and 80 amps. Hand-held models can be used to cut any conductive metal up to ½ inch thick (1.25cm) while industrial plasma cutters can cut through 2 inches (5cm) of metal.

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One of the advantages of using a plasma cutter is that the surface of the metal outside of the cutting area remains relatively cool; this prevents the warping and paint damage that can occur with other flame cutters. A thin heat affected zone (HAZ) also allows the use of templates for precise curved line cutting. Plasma cuts up to five times faster than traditional torches and does not rely on highly-flammable gases. Many plasma cutters also perform well as gougers and can pierce metal quickly and accurately.

Despite the advantages of plasma cutters, there are some drawbacks. The cutter's electrode and nozzle sometimes require frequent replacement which adds to the cost of operation. Non-conductive materials such as wood or plastic cannot be cut with plasma cutters. Another minor drawback is that the plasma arc typically leaves a 4-6 degree bevel on the cut edge; although this angle is almost invisible on thinner material, it is noticeable on thicker pieces. Gas fuel torches are considered better than plasma cutters for thick steel.

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anon77312
Post 6

how to calculate the life of nozzle and electrode in plasma cutting?

hthomas
Post 3

I have one of the small 220 Tig welders, is it feasible to convert this into a plasma cutter, if so, what would I need?

anon1156
Post 1

I am about to build my own plasma cutter/ welder. I know that input power 230 volts times 45 amps will sort of determine the output power, minus about 10 - 20 percent for transformer losses ect. Just because the way my transformer is wound, it will have an open secondary voltage of 41 volts, with about over 200 amps. The ac/dc stick welder part is easy to design, but I have no experiance with a plasma cutter. The output amperage seems to determine the max cutting thickness. The high freq. starting circuit is easy to make, but what is the minimum voltage that a plasma cutter arc needs? In case you are wondering, the transformer is out of a giant industrial 3 phase welder that put out 600 amps, using just the center coil it works like a single phase transformer, it will not burn out.

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