Effects of the EDM combined ultrasonic vibration on the machining properties of Si3N4

Abstract

The authors have previously performed numerous experiments on the machining of insulating materials using the assisting electrode method. However, the machining performance was inferior to that of the electrically conductive materials. To overcome this inferiority, for this research, an ultrasonic vibration system was combined with electrical discharge machining (USEDM) and applied with the assisting electrode method. Rotational machining was also added. A cylindrical copper tungsten bar was used as the electrode material for machining the sintered Si3N4 insulating ceramic. The effects of the electrode polarities, the effects of the amplitude on machining performance, the generation of a conductive layer and the discharge waveforms were investigated. The results were then compared to the conventional electrical discharge machining (normal EDM). The finishing process was performed by combining the ultrasonic vibration and various abrasive suspensions to remove the conductive layers and the craters. The results show that the material removal rate improved by a factor of approximately two over the normal EDM, and the surface roughness increased when the ultrasonic vibration was applied. The conductive layers and the craters were removed by the ultrasonic vibration using an abrasive (US+abrasive) method. The surface roughness of the workpiece was greatly improved by using the proposed method. ©2010 The Japan Institute of Metals.