Electrical Discharge Machining(EDM) is a process that uses electrical energy and thermal energy for processing, commonly known as electrical discharge machining.The difference between EDM and general machining is that the tool does not touch the workpiece during EDM, but the pulsed spark discharge that is continuously generated between the tool and the workpiece. The local and instantaneous high temperature is used to erode the metal material. There is visible spark during discharge, it is called EDM

Perforation processing is the most widely used in EDM, and is often used for processing holes (round holes, square holes, polygonal holes, shaped holes), curved holes, 4qL, micro holes, etc., such as cold die, wire drawing die, extrusion Various types of holes and small holes on the die, nozzle, and spinneret.The dimensional accuracy of the perforation is mainly ensured by the size of the tool electrode and the gap of the spark discharge. The cross-sectional profile of the electrode is uniformly reduced by a machining gap than the predetermined hole size, and the dimensional accuracy is higher than the workpiece, which is generally not low. At IT7, the surface roughness value is smaller than the workpiece, and the straightness, flatness and parallelism are not more than 0.01 mm over a length of 100 mm.

The electric spark cavity processing includes a forging die, a die-casting die, an extrusion die, a bakelite mold, a plastic die, and the like. Cavity machining is difficult, mainly because it does not pass through hole processing, the amount of metal erosion is large, the working fluid circulation and the electrolytic corrosion product are poorly excluded, and the tool electrode cannot be compensated by feed after the loss; the second is that the processing area changes greatly, and The cavity is complicated, the electrode loss is not uniform, and the processing precision is greatly affected.Therefore, the cavity processing productivity is low and the quality is difficult to ensure. In order to improve the processing accuracy of the cavity, in terms of the electrode, pure copper and graphite having high corrosion resistance are used as the electrode. In addition, the surface frosting of some small plastic molds also uses EDM.