Reducing Tool-Tip Wear in Micro ECDM Scanning Process with Feedback Control of Flexible Contact Force

Abstract

While machining the quartz glass in micro ECDM (electrochemical discharge machining) scanning process, the wear of tool electrode is adverse to machining accuracy. In this research, the developed spindle with servo feedback control of flexible force is used to avoid the instantaneous change of contact force that leads to the bending of tool electrode when the machining surface is uneven. The basic experiments are carried out through optimizing the processing parameters of open-circuit voltage, scanning speed, and scanning time, and then the mechanism and key influential factors of tool wear are analyzed. It is found that the tool wear is caused by the chemical reaction, the heat from discharges, and the friction between tool-electrode tip and workpiece surface. Therefore, three methods for reducing the tool wear are proposed and experimented. Method I: the low temperature electrolyte is applied in increasing the heat dissipation ratio of the tool-tip. Method II: the side wall of tool electrode is insulated by an oil film to constrain spark discharges only at the tool-tip bottom. Method III: more bubbles are pumped to promote the formation of gas film and the electrolyte renewal. Experimental results show the tool wear can be obviously reduced, so the machining accuracy of micro structures on quartz glass is improved in micro ECDM scanning process.