EDM toolings are used in electrical discharge machining (EDM), a highly accurate manufacturing process for creating shapes within components and assemblies. Tooling for EDM looks similar to that used for ultrasonic in that there is a shaped probe just above the surface of the ceramic. With the ceramic grounded and the probe charged, an electric spark erodes the ceramic surface. For this to happen, the ceramic has to be an electrical conductor, placing a restriction on where the technique is applicable.
Wire EDM is process whereby a wire typically .006 inch to .008 inch in diameter is electrically charged at a very high voltage and used to cut precision shapes in prismatic components. The wire is passes from one spool to another and is guided by and an upper and lower guide as it cuts. There are numerous advantages to wire EDM machining such as the ability to cut very precisely, cut nearly square internal corners and cut tapers that would be virtually impossible to cut otherwise.