Bionic stepped drilling and milling composite tool based on beetle mouthparts: A comprehensive analysis of machining mechanism and cutting performance

Abstract

Aramid fiber-reinforced polymer (AFRP), as a high-tech composite material with excellent performance, is widely used in the aerospace field, but it is prone to producing more machining defects in the drilling process, which seriously restricts the manufacturing accuracy and machining efficiency of the parts. In order to reduce the drilling damage of AFRP, a model of cutting of delamination damage was founded, the influencing factors of fibroid deformation were investigated, and a functional relationship between deformation and drilling force was acquired. On this basis, the cutting machining mechanism of the end mill and the drilling bit was analyzed, a material removal method of “centering and scratching” was proposed, and a stepped control scheme of “drilling before milling” was determined. Based on the tooth profile morphology of the beetle mouthparts, three kinds of tool structures with different rake angles were designed, the machining mechanism of the new cutters was researched, and comparative tests with various cutting tools and machining conditions were conducted. The research results showed that the new tools changed the removal mechanisms of the AFRP composite material within the cutting machining process of conventional tools and could reduce the cutting force while suppressing the delamination damage. Among them, the ${45}^{°}$ rake angle tool showed excellent cutting performance. The machining effects of burr-free holes, low delamination factor, and low tool wear were achieved within the range of test parameters. In addition, the cutting force was also lower, with a magnitude of $47.267\%$ of the milling force of an end mill and only $28.309\%$ of that of a drill bit. However, against the situation of minimum quantity lubrication (MQL), the cutting machining force increased significantly, which was about $4.706$ times that of the dry cutting test. The surface morphology was poor at this time, and the tool wear increased. In summary, the research content of this article will provide new ideas and methods for low-damage machining and specialized tool design of AFRP, and further clarify the cutting mechanism of this material under dry cutting and MQL machining conditions.