Simulation Analysis of the Crater Size for Single-pulse Dry Electrical Discharge Machining

Abstract

Electrical discharge machining (EDM) in a gas medium (dry EDM) is an environmentally friendly machining method. However, dry EDM mechanism is not well understood, which limits its development. Understanding the material removal mechanism using a simulation modality is constructive to the EDM mechanism analysis, and it could provide a theoretical support for further improvements in dry EDM performance. In EDM, the heat generated by the dielectric breakdown due to the high electrical field erodes workpiece material; therefore, the crater size is determined by the temperature of the single-pulse discharged. Despite the temperature field of a single-pulse not being completely equal to that of a continuous pulse discharge, the simulation of the temperature field and the study of the characteristics of the crater variation in a single-pulse discharge might provide favorable findings to understand the erosion mechanism of materials in dry EDM. Therefore, a simulation of the temperature field of a single-pulse was performed according to the established thermal transfer model using a finite element software. The center point temperature of the crater varying with discharge time, the evolution features of the crater diameter and crater depth under different pulse durations and peak currents, and the variation of the ratios of crater size by gasification to that by melting were analyzed. The simulation results indicate that when the discharge time was close to 50% of the pulse duration, the temperature of the discharge channel center began to decrease. The ratio of crater diameter by gasification to that by melting decreases with an increase in the pulse width and the discharge current. The experimental results validated the simulation analysis of the discharge crater size.