1. Electrical Methods of Material Removal Chapter 5

2. Competencies Identify the general operating principles of EDM

3. Electrical Methods of Material Removal Electrical Discharge Machining (EDM) - The process of removing metal with an electric arc. The workpiece and cathode (shape of tool/ impression) are submerged in a dielectric fluid Voltage is applied (DC 300V) Material is arced away and flushed out by the dielectric fluid Electrodes are usually made of graphite The material removal rate is influenced by the melting temperature of the workpiece material and is faster for materials of lower melting temperature.

4. Electrical Methods of Material Removal EDM is best suited for materials whose parts are: Made of very hard (conducting) materials and To have a high precision (or low surface roughness) At a low production rate To have some strange shapes which would be difficult to machine by conventional techniques

5. Electrical Methods of Material Removal RAM 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 to erode the sides of the hole to form two external surfaces, which can have an elaborate shape. wire electrode is of brass, copper, tungsten or molybdenum

6. Electrical Methods of Material Removal 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 materials.