Reducing tool-tip wear in micro-ECDM scanning process with feedback control of flexible contact force

While machining the quartz glass in the micro-ECDM (electrochemical discharge machining) scanning process, the wear of the 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 the 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 the tool electrode tip and the workpiece surface. Therefore, three methods for reducing tool wear are proposed and experimented with. Method I: the low-temperature electrolyte is applied to increase the heat dissipation ratio of the tool tip. Method II: the side wall of the 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 that the tool wear can be obviously reduced, so the machining accuracy of microstructures on quartz glass is improved in the micro-ECDM scanning process.