Reduction of Tool Wear in Non-contact Electrostatic Induction Feeding EDM

In this study, the authors aimed to decrease tool wear ratio in non-contact electrostatic induction feeding for micro electrical discharge machining (EDM). Since this electrostatic induction feeding method is capable of non-contact electric feeding to the tool electrode, the tool electrode can be rotated at a high speeds of 50,000rpm or more. Accordingly, both material removal rate and machining accuracy can be improved. With this method however, since discharges occur with alternating polarity, the tool electrode wear rate is higher than conventional unipolarity pulse discharge where the polarity of the workpiece is positive. Thus, in this study, circuit impedance was switched alternately to decrease the tool wear ratio, so that the discharge peak current becomes high when the workpiece is negatively charged, and low when positively charged. As a result, the tool wear ratio equivalent to conventional unipolarity discharge was achieved.