Resistance projection welding (RPW) is a variation of resistance welding in which current flow is concentrated at the contact surfaces of interest by an embossed, cold headed, or machined projection. The projection(s) effectively localize the current, forcing the parts to heat predominately at the mating surfaces. This rapid interfacial heating allows for the application of resistance projection welding across a wide range of applications not feasible by conventional resistance spot welding.
The projection is designed to localize current flow at the contact surfaces where the joint is desired. This focuses heat at the mating surfaces of the pieces and minimizes bulk heating of the parts. This rapid thermal cycle allows for precision joining of detailed parts, joining of metallurgically challenging materials, and formation of multiple welds simultaneously. While the projection usually collapses early in the weld cycle, the localized heating raises the material resistance locally and promotes further heating and finally weld development at the initial contact point. The process can be developed to produce a recast fusion type weld or a solid state weld depending of the application.
Because the formation of the weld is highly localized, the process is considerably more energy efficient than other resistance welding processes.