PLASMA ARC MACHINING OR PLASMA JET MACHINING (PAM)
We know that all gases burning at high temperatures are ionized gases. In plasma arc machining, the gases are ionised by placing an arc across the path of gas flow. The gas molecules get dissociated causing large amounts of thermal energy to be liberated. This generates temperatures of the order of 16500 deg. C, which are then utilized in removing metal by melting and vaporization. Figure below shows the schematic view of PAM.
An arc is struck between tungsten (or tungsten alloy) cathode and the water cooled copper (or copper alloy) anode. An inert gas such as argon is passed through a small chamber in which the arc is maintained. As the gas flows out the nozzle, it is heated and gets ionized by the arc and forms the moving plasma flame. The cathode is eroded by the high spark temperature and must be adjustable.
Applications
Plasma torches have been used for cutting and gouging in hard materials such as stainless steel. As compared to ordinary flame cutting torches, these can cut plain carbon steel four times faster.
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