High-quality hole machining in carbon fiber reinforced polymer by electrical discharge machining with side discharge suppression

Carbon fiber reinforced polymer (CFRP) machining by electrical discharge machining (EDM) frequently exhibits poor machining quality in the form of heat-affected zones (HAZ), overcutting, and taper, which severely limits the achievement of high-precision drilling. In this study, investigation into machining-induced damage revealed that oversized carbon fiber debris leads to frequent side discharges, which lead to machining defects. To overcome these limitations, an EDM method utilizing a side-insulated electrode was developed, accompanied by an in-situ preparation method for the side-insulated electrode. This method effectively suppresses side discharge, enhancing hole fabrication quality. The EDM process with side-insulated electrodes reduced side discharge frequency by 94.9% and significantly improved machining quality, including reductions of 58.7% in overcut, 76.8% in machining taper, and 79.2% in HAZ. Moreover, machining time was reduced by 40.9%, significantly improving overall machining efficiency, and the tool wear rate was also reduced by 41.5%. This approach offers a promising solution for high-quality EDM of CFRP. Highlights: Hole structure defects caused by side discharge are revealed. An innovative in-situ preparation method for side-insulated tool electrodes is proposed. Machining defects are suppressed and significantly improve processing quality. Machining efficiency is enhanced while minimizing tool wear.