Papers by Keyword: Sinking Electrical Discharge Machining

Abstract: Generally, all insulating materials were regarded as the non machinable workpiece for the electrical discharge machining (EDM) method. About twenty years ago, many insulating ceramics turned to the machinable materials for EDM using the assisting electrode method which was proposed by our research group. The machining mechanism was already explained with the surface adhesion phenomena [1]. In this process, many unstable discharge phenomena occurred such as concentrate, short circle and long pulse. It was clarified that they generated frequently on the high electrical resistance surface. The EDMed surface became rough and uneven on the unstable discharged area. In this paper, to obtain the good and even EDMed surface on the large removal area same as small area machining for Sinking-EDM, the effects of electrode size and shape were investigated. Considering the path of discharge supply energy on the high resistivity surface, new machining method was proposed which was named as the scanning machining method, and the ability of this method for practical use was confirmed with Si₃N₄ insulating ceramics. Using the new proposal method, better surface roughness and the sharp corner edge shape could be machined on the large area EDMed surface.

Abstract: Insulating ceramics were considered as machinable material with the electrical discharge machining method using the assisting electrode method, which was proposed and advanced by the authors. The mechanical properties changed with the experimental parameters, including the physical characteristics of the workpiece and the tool electrode. In this research, sintered ZrO2-Y2O3 insulating ceramics were subjected to EDM. To investigate the effects of the porous tool electrode material on the removal rate, the porous copper cylinder material was fabricated by PECS (pulse electric current sintering) method. The relative density changed from 60 to 95 wt%. The suitable machining characteristics could be obtained with a relative density of 85% at the positive electrode polarity. The shape of electrodes was transcribed on the workpiece surface more precisely than the solid copper electrode.