Abstract
Dielectric liquids such as kerosene based oils are generally preferred in the EDM process because such liquids are regarded as indispensable for material removal. As environmemtal hazards, cost, etc., are demerits with those liquids, the EDM without any such medium was thought to be important to explore. With this intention, the present study was formulated in which debris formation and their distribution on the working surface due to single pulse discharge in the EDM process under air and liquid (gelatin) were examined. Specifically, the EDM gap after single pulse discharge was monitored and during the process, total debris volume removed was measured. The position of scattered debris and their size distribution were also obtained.
In air, almost all the debris removed were scattered on the electrode surface, got attached there and solidified. In liquid, the scattered debris were, however, mainly distributed at the bound ary of bubble formed due to evaporation and disassociation of gelatin. The bubble formation in the liquid and their explosive expansion contributed to the material removal. Such contribution was found effective only when the pulse duration was less than 90μsec, whereas the material removal in liquid was almost the same as that of in air for a pulse duration longer than 90μsec. As far as the material removal is concerned, therefore, EDM may be performed in air provided the debris generated in the process be flushed out of the EDM gap before they get solidified on the electrode surface.
