**5. Modifications of resistance spot welding**

A modified version of resistance spot welding has been developed which is known as projection welding. The weld is localized in projection welding by using raised areas, or projections, on one or both of the metal sheets to be connected. Heat is concentrated at these projections, allowing for the welding of heavier parts or closer weld spacing. The projections can also be used to position the workpieces so that they are balanced. Studs, nuts, and other threaded machine parts are frequently welded to a metal plate using projection welding. Crossed wires and bars are typically joined with it. Multiple projection welds can be arranged by appropriate planning and jigging in this high-production technique [34].
