Another drawback is that the electrodes used for welding need to be dressed periodically. As tooling wears or as setup changes are required, an operator may have to spend up to 20 minutes replacing electrodes. Due to contamination buildup, there also can be variations from part to part as the electrodes wear. In addition, resistance welders are heat-intensive machines. When too much builds up during the welding of wires, the splice can be damaged. Chilled water must be chlorinated through the tooling to prevent excessive heat buildup. A side effect of the chilled water cooling of the tooling is the accumulation of condensation on the chilled surfaces.
The third method, ultrasonic splice welding, metallurgically bonds stranded copper wires to form a homogenous mass. The wires to be joined are placed between a tip and an anvil by the operator, and the weld cycle is started. An air cylinder advances an ultrasonic stack to compact the wire within the pocket formed by a gathering block, a tip, and the anvil. An ultrasonic generator and horn convert conventional AC line voltage to 20 kHz mechanical vibrations in the tooling. The vibration is transmitted through the tip in a plane parallel to the weld interface. This includes minute alternating displacements of 18 to 72 microns between mating surfaces. This scrubbing action disrupts and disperses most oxides and other surface coatings, exposing clean, bare metal. The cleaned surfaces, forced together under pressure and vibrating at high frequency, bond metallurgically. At the completion of the timed cycle, the tip and gathering device retract.
