A Theory and Evaluation of Tool-Electrode Shape Degeneration in Electro-Discharge Machining

Abstract

An analytical approach is presented which provides the basis of the numerical analysis method for computation of tool-electrode shape degeneration in electro-discharge machining (e.d.m.). Following earlier work, the concept of ‘relative duty’ of the electrodes is utilized, and is found to predict the type, and to a less satisfactory degree the extent, of degeneration. Further experimental work confirms that the effect of local profile curvature on the local tool/work erosion ratio is greater than that suggested by the geometrical ‘relative duty’ concept. Subsequent incorporation of the empirical results of these tests into the numerical analysis brings the predicted shape degeneration behaviour into quite close agreement with experiment. Computed electrode profiles showing degeneration at different periods of elapsed sparking time are presented, together with the experimentally observed cases for comparison.