Resistive spot welding (RSW) is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current. The process uses two shaped copper alloy electrodes to concentrate welding current into a small “spot” and to simultaneously clamp the sheets together. Forcing a large current through the spot will melt the metal and form the weld.
This DIY battery tab resistance fine-spot welder is built and designed by Albert van Dalen. The project has very simple construction and accurate electrode force adjustment. It comes with a solid electrode holder, made of a radiator earthing clamp. For welding sensitive parts, the current can be reduced. It creates a double pulse which improves clamping.
The project uses an inverse parallel SCR instead of TRIACs because SCR gives better works at inductive loads. The spot welder controller is built based on Arduino Uno. Light duty portable spot welding guns have a welding current of at least 4000A, which allow welding of 2 x 1mm low carbon steel sheets. The DIY spot welder just delivers 1100A, which is fine for welding small electronic parts.