Effect of EDM process parameters on 3D surface topography

The electro discharge machining (EDM) process is a violent thermal process where literally thousands of electrical discharges are produced in a fraction of a second in order to erode a certain volume of metal. The process is mostly used in situations where intricate complex shapes need to be machined in very hard materials (such as hardened tool steel). However, the process generates surfaces that have poor properties such as high tensile residual stresses, high surface roughness, presence of cracks and microcracks. These properties vary with different levels of the main process parameters. The aim of this paper is to present experimental work that has been done in order to quantify the effect of some of the main EDM parameters on the surface texture. 3D surface measurements were taken on all EDM samples, and 3D surface characterisation has been carried out in order to calculate the different surface texture parameters. The results have shown that the pulse current is the most dominant factor in affecting the surface texture. Moreover, the interaction effect between pulse current and its duration on the 3D surface roughness parameters is relatively small. It has also been observed that the Sq, Sm, Sc and Sv 3D surface parameters are more sensitive to the process variables.