A comparative study on the surface integrity of single-step and multi-step sequential machining in electric discharge machining

Abstract

In the past, the effect of electrical parameters, dielectric, and electrode material and shape on surface integrity in electric discharge machining (EDM) was widely studied by scholars. However, these researches are mainly based on single-step EDM that can be categorized into either roughing or finishing. The production of components by EDM is a process from roughing to finishing in industry, which is a multi-step machining process. Therefore, in order to provide a better guideline for the fabrication of parts through the single-step EDM approach (refers to the last step of multi-step machining in this study), it is necessary to investigate and quantify the difference in surface integrity between single-step and multi-step sequential machining. In this study, the surface integrity of single-step and multi-step machined samples is evaluated and compared. The results demonstrate that the surface roughness, white layer thickness, and surface residual stress of multi-step machined samples are higher than those of single-step machined samples. In the finishing stage, the difference in surface roughness and residual stress between them becomes even larger. It was indicated that the surface state of the sample obtained in the previous processing steps has an influence on the final machining quality during multi-step sequential EDM. In addition, the change of the surface morphology of the tool electrode caused by the previous machining steps would also affect the surface roughness of the workpiece processed in the current step. There is no significant difference in the crystalline phase between single-step and multi-step sequential machining.