Single Discharge Machining Insulating Al2O3 Ceramic with High Instantaneous Pulse Energy in Kerosene

A technique of machining insulating Al2O3 ceramic with a thin copper sheet assisting electrode and high instantaneous pulse energy is developed. The process uses the high peak voltage and large capacitor with high instantaneous pulse energy, and there is no current-limiting resistor in the discharge circuit, so the discharge energy and discharge explosive force are high, and the process is able to effectively machine insulating ceramics. To further explore the process characteristics, the single pulse discharge experiments have been carried out in kerosene. The effects of polarity, capacitance, peak voltage, and current-limiting resistance on the process performance such as the crater volume, crater depth, tool wear ratio (TWR), and assisting electrode wear ratio (AEWR) have been investigated. The microstructure of the discharge crater has been examined with a scanning electron microscope (SEM). The results show that the insulating Al2O3 ceramic materials are mostly removed by spalling, at the center region of the discharge some materials are removed by melting and evaporation.