Pulsed laser focusing for triggering arc discharge in an arc welding system

In tungsten inert gas (TIG) arc welding systems, arc plasma is generated between the cathode (tungsten rod) and anode (workpiece).¹ Availability of a dependable technique for triggering arc discharge is indispensable for production processes using arc welding. Typical conventional triggering techniques include the high-frequency, high-voltage and touch-start methods. The high-frequency and high-voltage methods involve arc discharge being triggered through ionization of the gas present between the electrodes by means of a conventional high-frequency generator or high-voltage DC generator.² The high-frequency method, however, may possibly disrupt operation of peripheral computer systems, whereas the high-voltage method involves suitable electric circuits being arranged inside the power source to prevent high voltage-related accidents.^{2, 3} After the rod is lowered to make contact with the workpiece in the touch-start method, it is quickly withdrawn to trigger the arc. This method obviates the need for any power source other than the arc welding power source. An important advantage of the touch-start method therefore is its simplicity. When the rod is withdrawn, however, part of it (tungsten) may sustain melt-through to the workpiece in a way that adversely affects weld quality. This is a disadvantage of the touch-start method.₃