Micro-holes machining characteristics of Cf-ZrB₂-SiC by Micro-EDM and taper control based on swing device

Abstract

Cf-ZrB2-SiC is a new composite material with excellent properties for making next-generation aerospace components. Micro-holes in this material are extremely difficult to machine using mechanical processing methods, and there is a lack of research on feasible machining methods of Cf-ZrB2-SiC micro-holes, at present. On the other hand, micro electrical discharge machining is not limited by material hardness and is suitable for deep hole machining. In this paper, the machining characteristics of Cf-ZrB2-SiC micro-holes using micro-EDM are analyzed, after validating the processability of micro-EDM for this material. Based on polarity experiments and electrical parameter tests, feasible strategies for roughing and finishing are proposed. Nevertheless, the processed through holes and blind holes exhibit defects. Processing debris is collected and analyzed to reveal the causes of these defects. To address the issues of processing taper and machining defects, a swing device is developed as an auxiliary method, which not only can control the machining taper and successfully fabricate micro-holes with positive taper, inverted taper or no taper, but can also improve the processing metrics such as discharge stability, surface quality, and depth-to-diameter ratio. Notably, a maximum depth-to-diameter ratio of 13.1 can be achieved, which is 56 % higher than general method. Furthermore, it is found that the through hole and blind hole with a diameter of 750 μm and no taper can be successfully machined using on the swing device without the machining defects.