CHAPTER 5 – ELECTRICAL METHODS OF MATERIALREMOVALElectrical Discharge Machining (EDM) - The process of removing metal with an electric arc.a) The workpiece and cathode (shape of tool/ impression) are submergedin a dielectric fluid b) Voltage is applied (DC 300V)c) Material is arced away and flushed out by the dielectric fluidd) Electrodes are usually made of graphite EDM is best suited for parts that to be made of very hard (conducting) materials and to a high precision (or low surface roughness), at a low production rate, and having some strange shapes which would be difficult to machine by conventional techniquesRAM EDM= Plunge EDM = Die Sinking EDM - complex cavities are formed by penetration of shaped electrode into the part. Used to make dies for forging or punching operations. Wire EDM- Uses a wire (passed through a previously formed hole or started from the edge of the material) to erode the sides of the hole to form two external surfaces, which can have an elaborate shape. (electrode is a brass, copper, tungsten or molywire).Skimming – A final light pass for polishing or to meet dimensional tolerances.Electric Discharge Grinding (EDG) is a gentle process excellent for thin materials.Advantages over faster methods of material removal: - Unaffected by the hardness of the workpiece. - Holes with extremely complex shapes can be made. - There is no distortion of the metal, and no burrs left. - Produces surfaces to very fine dimensional and roughness tolerances- EDM operates unattended. Disadvantages: EDM is slow, expensive, and cannot be used on nonconductive
View Full Document
Unlocking...