In tandem pulsed GMA welding, it is most important issue to prevent arc interruption caused by electromagnetic interference between the two arcs. Pulse timing control can reduce arc interference in tandem pulsed GMA welding. One effective way is to delay the pulse end timing of trailing arc by 0.4-0.5 ms from that of leading arc. In addition, arc length control is assured by pulse frequency modulation (PFM) for the leading wire and pulse peak modulation (PPM) for the trailing wire with the pulse timing synchronized with the leading pulse. Consequently, leading and trailing arcs are maintained stable without arc interruption and a stable arc length control is established, which is hardly affected by fluctuations of wire feed rate and extension length.
