Working Principle of EDM

The working principle of EDM process is based on the thermoelectric energy. This energy iscreated between a workpiece and an electrode submerged in a dielectric fluid with the passage ofelectric current. The workpiece and the electrode are separated by a specific small gap calledspark gap. Pulsed arc discharges occur in this gap filled with an insulating medium, preferably adielectric liquid like hydrocarbon oil or de-ionized (de-mineralized) water [4-7][4] Rudorff, D.W., 1961 Spark machining and its development, Metal Treatment and DropForging, 28 (186), 120124.[5] Pandey, P.C.; Shan, H.S. Modern Machining Process. Tata McGraw- Hill PublishingCompany Ltd 1999, 84-113.[6] Smith, G.V., 1961, Spark machining fundamental and techniques. J Br Inst Radio Eng,22, 409.[7] Luis, C.J., Puertas, I., Villa, G., 2005 Material removal rate and electrode wear study onthe EDM of silicon carbide, Journal of Materials Processing Technology, 164165, 889

The working principle of EDM is shown in Fig. 1. This technique has been developed in the late1940s [8][8] Singh, S., Maheshwari, S., Pandey, P.C., 2004 Some investigations into the electricdischarge machining of hardened tool steel using different electrode materials, Journal ofMaterials Processing Technology, 149, 272277.

The electrode moves toward the work piece reducing the spark gap so that the appliedvoltage is high enough to ionize the dielectric fluid [9].

[9] Bojorquez, B., Marloth, R.T., Es-Said, O.S., 2002 Formation of a crater in the workpieceon an electrical discharge machine, Engineering Failure Analysis, 9, 9397.

Short duration discharges are generated in a liquid dielectric gap, which separates electrode and work piece. The material is removed from tool and work piece with the erosive effect of the electrical discharges [10]. Melting and vaporization takes place by theses electrical discharges. The minute a mounts of the work material is then ejected and flushed away by the dielectric medium. The sparks occur at high frequency which continuously and effectively removes the work prices material by melting and evaporation.[10] Marafona, J.; Chousal, A.G., 2006 A finite element model of EDM based on the Jouleeffect, Int. J. Mach. Tools Manuf., 46 (6), 595-602.