Suppression of cathode tool wear by a forward-bias voltage in pulsed spark-assisted chemical engraving

Abstract

Pulsed spark-assisted chemical engraving (SACE) is a promising technology for micromachining of insulating materials, with no burrs, no cracks and no residues left after processing. Cathode tool wear, however, is one of the problems that must be overcome to enable large-scale application of SACE. This paper presents a comprehensive study of the phenomena and mechanisms involved in cathode tool wear in pulsed SACE. By analyzing the electrolytic current and pulsed voltage waveform during the process, it is demonstrated that cathode tool wear is determined by the reverse current and is particularly affected by the pulse-off time and applied voltage. A longer pulse-off time results in more significant tool wear. The reverse current is mainly caused by the discharge of electrical double layer capacity when a pulsed voltage is applied. By applying a forward-bias voltage during the pulse-off time, cathode tool wear can be completely suppressed. The research results of this paper provide a reference for prevention of tool wear in precision micromachining with the pulsed SACE method. Keywords: Spark-assisted chemical engraving, Cathode tool wear, Reverse current, Forward-bias voltage, Electrical double layer capacity, Equilibrium electrode potential