Surface roughness model for micro electrical discharge machining

Abstract

Asperities produced by electrical discharge machining (EDM) are covered by a multitude of overlapping craters, which results in the formation of corresponding workpiece profiles with a specified accuracy and surface finish. This paper proposes a surface roughness model for micro-EDM based on the crater geometry estimation. Surface factors are introduced into the model formulation to take into account the effects of overlapping craters, pockmarks, microcracks, and reattachment of debris in the actual machining process. Based on the experimental results using AISI 4140 as the workpiece, the surface factors are found to be 0.2985 and 0.3443 for the theoretical surface roughness for Ra and Rt respectively. Extension of the surface roughness prediction model to other materials is demonstrated using Ti—6Al—4V. Through this preliminary study, the proposed model generated theoretical results that have an average error of 6.5 per cent for Ra and 4.5 per cent for Rt when compared with the respective experimental results, thereby revealing the potential usefulness of the surface roughness prediction model.