Study on the Distribution of Scattered Debris Generated by a Single Pulse Discharge in EDM Process

Abstract

Dielectric liquids such as kerosene based oils are regarded as indispensable for material removal in the EDM process. As environmental hazards, cost, etc., are drawbacks of the use of these liquids, the properties of an EDM without using such liquids are thought to be an important area to explore. With this in mind, the present research was formulated to study debris formation and their distribution on the working surface due to a single pulse discharge in air and in liquid(gelatin). In air, almost all the debris removed are scattered radially around the discharge spot and then attaching and solidifying on the electrode surface. In liquid, the scattered debris are, however, mainly distributed at the boundary of the bubble formed due to evaporation and dissociation of the gelatin. The bubble formation in the liquid contributes to the material removal. This contribution is found effective only when the pulse duration is less than 90 fJ. s, whereas the material removal in liquid is almost the same as that of in air for a pulse duration longer than 90 fJ. s. As far as the material removal is concerned, therefore, EDM may be performed in air provided the debris generated in the process can be flushed out of the EDM gap before it solidifies on the electrode surface.