A new technique for electrochemical self-discharge machining of macro-sized hole in the glass using an integrated tool electrode

Owing to stray electrochemical discharge effects, it is still a significant challenge to obtain high machining quality and efficiency in conventional electrochemical discharge machining (ECDM) of macro-sized holes (>1 mm) in glass. Thus, in this study, an electrochemical self-discharge machining (EC-SDM) technique using an integrated tool electrode is proposed. In the new design, the tool anode and cathode are configured coaxially in an integral manner. The simulation and high-speed camera observation results indicated that the electrochemical discharges were more concentrated at the tool electrode end when using the EC-SDM. Thus, the stray electrochemical discharge capacity decreased significantly. With the formation of a dense oxidized layer on the anode electrode surface, the EC-SDM technique is frequently interrupted by DC pulse; however, the discharge is continuous under bipolar pulse conditions. Furthermore, the EC-SDM technique can utilize the advantage of the hydrogen-oxygen gas mixture generated at the integrated electrode end for combustion close to the workpiece surface, thus increasing machining efficiency. When compared with the conventional ECDM, the machining efficiency increased by 6.09 times, and the entrance heat affected zone (HAZ) reduced by 54.05 %. A macro-sized hole (entrance diameter of 1303 μm) with depth of 1520 μm, minimal thermal and mechanical damage was successfully obtained in the glass substrate by using the EC-SDM technique. The results illustrate that employing the novel EC-SDM technique is a straightforward way to reduce stray electrochemical discharge and improve the machining performance of macro-sized glass holes. The potential of the EC-SDM technique for MEMS applications was also highlighted.