What is resistance spot welding and why is it widely used in automotive manufacturing?

Resistance spot welding (RSW) joins metal sheets by applying pressure and passing high current through the workpieces, generating heat at the interface to create a weld nugget. It is widely used because: High speed (each weld takes <1 second), no filler material required, easily automated with robots, produces strong joints suitable for sheet metal, minimal distortion compared to arc welding, and cost-effective at high volumes. Modern vehicles contain 3000-5000 spot welds. Quality depends on current, time, electrode force, and electrode condition. Variations include projection welding and seam welding for specific applications.