Transient dynamics simulation of the electrical discharge-generated bubble in sinking EDM

Abstract

The evolution of bubble generated by electrical discharge in sinking electrical discharge machining (EDM) occurs in a very short time period and in a very narrow space, thus making both observation and theoretical analysis extremely difficult. For this reason, the role of the discharge-generated bubble during the material removal process in sinking EDM has not to be understood very clearly. In this paper, the evolution process of the discharge-generated bubble was simulated in three dimensions and the influence of inter-electrode distance was studied. It was found that the evolution of the discharge-generated bubble was significantly affected by the inter-electrode distance. Smaller inter-electrode distances can contribute to a larger pressure and expansion velocity of the bubble as well as a larger force applied on the tool electrode and workpiece. The experimental results showed that the geometry characteristics of the crater were also significantly affected by inter-electrode distance. A smaller inter-electrodes distance can contribute to a larger volume of both melted and removed materials. The simulation results were discussed by relating to the results of single-pulse discharge experiments; some insightful views about the material removal mechanism of EDM were presented in this paper.