PURPOSE:To suppress the production of double arcs at the starting of main arc and prevent damaging of nozzle by adding dissimilar operating gas after the start of the plasma arc produced in the operating gas flow. CONSTITUTION:Operating gas PG is beforehand supplied and a main arc 4 is produced at the welding work start point a. While the main current thereof is being detected, the current is shifted from the cutting start current Ip1 of small current to plasma cutting main current Ip. This current shifting involves increasing the current from the current Ip1 to the current Ip during the slow up time Ta and this time Ta is arbitrarily variable. For the gas PG, the operating gas of the same gas is supplied as the initial operating gas PG1 and at the time a, the second operating gases PG2 and PG3' are increased within the shift mode range of the time Ta. Namely, the gas PG is increased in the small current region and therefore rapid unstabilizing of the arc is obviated and the stable main arc shifting and the prevention of the formation of double arcs 6, 6' are accomplished. In the figure, 1 denotes a torch, 2 an electrode, 3 a base metal and 5 a nozzle, respectively.

Plasma arc cutting start method

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Plasma arc starting method

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Starting method of active gas plasma arc cutting

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