Spot welding

Spot welding is a resistance welding process in which two overlapping sheets are joined by simultaneously applying pressure and a high-current pulse through two opposing electrodes. The electrical contact resistance between the sheets generates localised heat — the molten nugget — which upon solidification creates a point metallurgical joint of high strength without filler material and without a visible arc.

The fundamental advantage is speed: each spot is completed in tenths of a second, making the technology indispensable for mass production of car bodies, domestic appliances and sheet-metal components. Machines range from large stationary pedal-operated welders to portable body-repair guns. In the maker and electronics context, spot welders for battery cells (nickel strip spot welders) are widely used tools for assembling lithium battery packs, where the brief, localised heat avoids thermal damage to the cells.