The heat may cause the materials to fuse locally and form a nugget at the interface or may be just high enough to produce a solid-state bond. The materials to be welded have to be held together with a clamping force, a job which is usually done by the resistance welding electrodes themselves. A modification of the resistance welding process is percussion welding, a process during which heat is generated by an arc between the two parts. With this process, we are able to join dissimilar materials. EWI has many power supplies to choose from including AC welders, DC welders, capacitive discharge welders, and high-frequency inverter power supplies.
PAW works in two basic methods, transferred and non-transferred arc methods.
A flowing plasma gas is provided through the center of the torch and exits through a copper nozzle. When an arc is established between the tungsten electrode positioned within the body of the torch and the copper nozzle, the gas is ionized, forming a high-temperature plasma. The arc can be transferred to the workpiece where the intense heat causes fusion and a weld is produced. In the microjoining lab, EWI has a microPAW system capable of as much as 50 amps. Pulsing is also available, with pulses from 1 to 999 Hz.