Monitoring the Percussive Welding Process for Attaching Wires to Terminals

The low-voltage percussive welding process as applied to wired connections has been described and its irerits pointed out in previous papers. 1-6 Therefore, only a brief review is included here. Percussive welding is a form of capacitor discharge arc welding. The parts being welded, in this case a wire and a terminal, are themselves the only necessary electrodes (see Fig. 1). Also, the only advance preparation of the electrodes needed is to cut a tip on the wire end. The weld is made by propelling the wire across a 50-volt gap toward the terminal. When the two are nearly touching, an arc is established between the wire tip and the terminal. Initially, the power surge in the arc develops sufficient heat to melt back the wire tip faster than the electrodes are closing. But, with time, the power decays and melting slows down until eventually the electrodes impact, extinguishing the arc and completing the weld. A welding voltage of 50 volts is commonly referred to as "low voltage" as opposed to "high-voltage percussive welding" used to attach the fixed contacts to the wires of the wire spring relay. 55