Projection welding is a multi-spot-welding process. Introduction to spot welding process: In resistance spot welding, two or more sheets of metal are held between electrodes through which welding current is supplied for a definite time and also force is exerted on work-pieces.

A multi-spot welder is a type of welding machine that can perform multiple spot welds at the same time. It makes multiple welds at the same time by using multiple welding electrodes arranged in a pattern.