A review of the current understanding and technology of powder mixed electrical discharge machining (PMEDM)

This paper reviews the current understanding of powder mixed electrical discharge machining (PMEDM), highlighting particularly the mechanisms proposed for PMEDM under the influence of additive of powders in the dielectric fluids. Generally, the mirror surface phenomenon in PMEDM can be explained by the enlarged gap widths which can expand the discharge channel and thereby reduce the electrical power density since lower power density can yield large and shallow craters that evenly distributed on the machined surface. Moreover, the increment of the inter electrodes distance will limit the capacitive effect and enable a small surface roughness even in a large area. Another possible mechanism, multi-discharge model was also presented in this paper. More investigations on the fundamental mechanism in power mixed EDM are highly desirable since it has not been understood clearly. In this paper, the traditional and some recent development technology for PMEDM is also reviewed. Historically, PMEDM was invented to improve the surface quality of the machined components. Nowadays, some new applications of this technology, such as micro machining, rough machining and surface modification were proposed; some novel variations that based on power mixed EDM, such as PMEDM combined with ultrasonic or abrasive, powder mixed near-dry EDM and powder mixed electrical chemical discharge machining (ECDM) were also developed.