Molecular dynamics simulation of the material removal mechanism in micro-EDM

Electrical discharge phenomena in EDM occur 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 material removal mechanism in EDM has yet to be understood clearly In this paper the forming process of discharge craters in three dimensions was simulated and material removal mechanism in EDM was analyzed using Molecular Dynamics (MD) It was found that material removal mechanism in EDM can be explained in two ways one by vaporization and the other by the bubble eklosion of superheated metals It was also found that the metal removal efficiency is 0 02-0 05 leaving most of the melted pool resolidified In addition the influence of power density on the removal process was Investigated and the results showed that as the power density Increases the diameter and depth of the melted area Increase as does the metal removal efficiency In this study the forming mechanism of the bulge around discharge craters was also analyzed and it was found that bulge is formed due to two mechanisms The first is the shearing flow of the molten material caused by the extremely high pressure in the superheated material and the second is the accumulation of the ejected material on the bulge formed by the first forming mechanism It was also found that existence of micro pores in the workpiece material increases the depth of the discharge crater and melted area thereby Increasing the machining surface roughness Simulation of the distribution of removed materials in the gap showed that some part of the removed material becomes debris ejected from the gap while another part settles on the surface of the opposite electrode and the last part returns to the surface of the electrode from which it was ejected (C) 2010 Elsevier Inc All rights reserved