Thermal analysis of EDM wire process

This paper attempts to explain why late breakage occurs in EDM wire machining. An energy balance drawn on the moving wire using a quasi-steady state viewpoint shows forced convection as the major cooling mechanism for the wire. A detail analysis of the forced convection gives estimation of the overall average wire temperature to be 57+/-12 degrees C. A quasi-steady state analysis was made to provide the temperature profile T(x) of the wire in the work zone provided that the sparks are equally distributed in both the axial (x) and peripheral (theta) directions. A dynamic analysis of multiple, sequential sparks in the same location on the wire estimates the hot spot about 73 degrees C after one spark, 93 degrees C after two sparks, 110 degrees C after three sparks, and 195 degrees C after eight sparks. The analysis is quantitative so final apriori predictions are made from a model without tuned parameters; the predictions are in excellent agreement with experimental measurements from the literature and our laboratory.