Molecular Dynamics Simulation Of Discharge Removal In Micro Edm Using Minimal Discharge Energy

Since the former Soviet UnionБ.Р.Лазаренкоcouples invented the EDM in 1943, this technical, a non-contact machining technique with little cutting force, have got a huge development and established its advantage station in the fields of micromachining. However, 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,especially in micro-EDM.In EDM, thermal energy generated by a pulse discharge between the workpiece and tool electrode results in melting and evaporation followed by material removal of both the workpiece and tool electrode, forming a crater on both surfaces. 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). The forming mechanism of the bulge around discharge craters was also analyzed. The first part of the removed material becomes debris in the gap, the second 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. The trajectories and distributions of the removed material in the discharge gap were analyzed using Molecular Dynamics. In addition, the volume and atom number of the anode and cathode after forming the discharge crater were analyzed. It was found that the volume of electrode may increase even though the material of electrode is removed when a discharge crater is formed because of the change of the arrangements and distances of electrode material atoms at the discharge location.Furthermore, material micro-structure is one of the possible factors determining the limits of minimum machinable size in micro-EDM. In this paper, influences of anisotropy of single-crystal atomic structure on the forming process of discharge craters were investigated. Shape dimensions of discharge craters generated on the planes of {100}, {110} and {111} orientations were obtained from the results of the molecular dynamics simulation. In addition, influences of micro defects like micro cracks and pores pre-existent in the workpiece material prior to occurrence of discharge on the forming process of craters were studied using Molecular Dynamics.