Electrical discharge machining

Electrical discharge machining is a method of working extremely hard materials or materials that are difficult to machine cleanly using conventional methods. It is limited, however, to electrically conductive materials. EDM can cut small or odd-shaped angles, intricate cavities or intricate contours in extremely hard steel and exotic metals such as titanium, hastalloy[?], kovar[?], inconel[?], hard tool steels, and carbide.

Sometimes referred to as spark machining, EDM is a nontraditional method of removing metal by a series of rapidly recurring electrical discharges between an electrode (the cutting tool) and the work piece in the presence of a dielectric field. The ensuing chips are removed by melting and vaporization, and are washed away by the continuously flushing dielectric fluid. Consecutive electrical discharges produce a series of micro-craters on the work piece until the desired shape is achieved.

The EDM process is most widely used by the mold-making tool and die industries, but is becoming a common method of making prototype and production parts, especially in the aerospace and electronics industries in which production quantities are relatively low.