The three basic types of resistance welding bonds are spot, projection, and seam. Each type has its own unique characteristics that make it best suited for different applications.
Spot Welding: Spot welding is the most common type of resistance welding. It is used to join two pieces of metal together at a single point. A spot welder has two electrode tips that come together at the workpiece to create the weld. The size of the nugget (the area where the metals are joined together) is determined by the size of the electrode tips, the amount of current, and the time that the current is applied.
Projection Welding: Projection welding is similar to spot welding, but instead of using two electrode tips, only one tip is used. The other side of the weld is created by a metal projection that extends from one of the workpieces. This projection makes contact with the other workpiece and creates friction that heats up both pieces of metal and causes them to weld together.
Seam Welding: Seam welding is used to join two pieces of metal along a continuous seam. A seam welder looks like a large version of a spot welder with two rotating wheels instead of electrode tips. The wheels press against each side of the seam and apply heat and pressure until both sides are joined together.