Electrical discharge machining (EDM) is a new process that uses electric energy and heat energy for machining, commonly known as EDM. The difference between EDM and general cutting machining is that during EDM, the tool and workpiece do not contact, but rely on the continuous pulse spark discharge between the tool and workpiece, and use the local and instantaneous high temperature generated during discharge to gradually erode the metal materials. Because there are visible sparks in the discharge process, it is called EDM.
Perforation machining is one of the most widely used in EDM. It is often used to process shaped holes (round holes, square holes, polygonal holes, special-shaped holes), curved holes, 4ql, micropores, etc., such as various shaped holes and small holes on cold stamping dies, wire drawing dies, extrusion dies, nozzles and spinnerets.
The dimensional accuracy of perforation is mainly guaranteed by the size of tool electrode and spark discharge gap. The cross-sectional profile size of electrode shall be uniformly reduced by one machining gap compared with the size of pre processed hole. Its dimensional accuracy shall be one level higher than that of workpiece, generally not lower than it7 level. The surface roughness value shall be smaller than that of workpiece, and the straightness Flatness and parallelism shall not be greater than 0.01mm over a length of 100mm.
EDM cavity machining includes forging die, die casting die, extrusion die, bakelite die, plastic die, etc. The cavity processing is difficult, mainly because it is through hole processing, the amount of metal corrosion is large, the working fluid circulation and the elimination conditions of electric corrosion products are poor, and the tool electrode can not be compensated by feeding after loss; Secondly, the machining area changes greatly, and due to the complex cavity and uneven electrode loss, it has a great impact on the machining accuracy. Therefore, the machining productivity of the cavity is low and the quality is difficult to ensure. In order to improve the machining accuracy of the cavity, pure copper and graphite with high corrosion resistance should be used as electrodes. In addition, EDM is also used for surface sanding of some small plastic molds.
