Study on single-discharge machining characteristics of non-conductive engineering ceramics in emulsion with high open voltage and large capacitor

Abstract

This paper presents a new process for the machining of non-conductive engineering ceramics that is based on electrical discharge machining. It uses a thin copper sheet as an assisting electrode and a high capacitance value capacitor that is directly discharged into the machining process i.e. there are no current-limiting resistors in the discharge circuit. This configuration creates a high discharge energy and discharge force which enables electronically insulating engineering ceramics to be effectively machined. Single-discharge experiments were performed using an emulsion as the dielectric machining fluid. The effects of the dielectric fluid, polarity, open voltage, capacitance, and current-limiting resistance on the process performance in terms of the volume and depth of the crater created in the surface of the workpiece, tool wear, and assisting electrode wear were investigated. In addition, the microstructure of the crater was examined using a scanning electron microscope. The results show that the crater is the result of a spalling process on the surface of the non-conducting ceramic workpiece. However, at the centre region of the crater some material is removed by melting and vaporization, and this type of material removal is enhanced by an increase in the open voltage.