High-Precision Small-Diameter Deep Hole Drilling Using Cooling and Step Feed in PEEK Resin

Abstract

The objective of this study is to achieve a high-precision and high-efficiency machining process for industrial components of the polyether ether ketone (PEEK) resin, such as the inspection socket of a connector or semiconductor packages. However, the drilling of holes in PEEK resin is challenging. Because PEEK resin is a thermoplastic resin, it can soften or melt owing to the heat generated during processing, which causes burrs and degrades the accuracy of the machined hole, thereby resulting in quality deterioration and hindering post-processing. Since the thermal conductivity of plastic materials including PEEK resin is lower than those of metals, the heat generated during processing does not dissipate to the outside of the workpiece, and the effect of the processing temperature on the processing accuracy is significant, particularly during drilling. Hence, a workpiece is cooled via a cold gas supply in this study. The effect of cold gas cooling on the machined hole accuracy and cutting state in the small-hole machining of PEEK resin is investigated. Results show that cooling the workpiece effectively decreases the cutting temperature and improves the machined hole accuracy. Under the experimental conditions, the combination of nonstep drilling and cooling enables high-precision drilling at approximately the same accuracy as step drilling.