Kerosene Supply Effect on Performance of Aluminum Nitride Micro-Electrical Discharge Machining

Abstract

As interest in aluminum nitride (AlN), a high-performance ceramic, has been rapidly increasing, many researchers studied the possibilities of machining it. Since AlN is classified as a difficult-to-cut material, the electrical discharge machining (EDM) process using an assisting electrode is emerging as an effective machining method. Kerosene, as a dielectric fluid, plays an important role in forming a successive conductive carbon layer on the surface of the workpiece to induce and maintain discharge. Most previous methods used tubular electrodes to stably feed the dielectric fluids through their center hole. However, in the case of micro-EDM, the extremely small electrode diameter makes it difficult to fabricate a through-hole in the electrode, and a very narrow gap prevents the flow of dielectric fluid. In order to overcome dielectric fluid flow problems in micro-EDM, in this study, two kinds of flow-promoting methods are introduced: one is to use a D-shaped solid electrode to obtain a wider asymmetric flow channel, and the other is to use an O-shaped solid electrode with graphite-powder-mixed kerosene (GPMK) under a relatively wider discharge gap. Flow simulation results show that both methods promote kerosene flow, and the experimental results show similar results as well. When using the D-shaped section, the material removal rate increased, but increased tool wear was observed. In the case of GPMK, the metal removal rate increased 64%, and relative wear ratio decreased 73% compared to conventional methods. Through voltage scheduling, the problem of precision degradation that occurs during deep-hole drilling with the O-shaped solid electrode GPMK configuration was solved without sacrificing machinability.