Theoretical and Experimental Study on the Surface Microstructures of Polyimide in Ultra-Precision Fly-Cutting.

Polyimide (PI) with surface microstructures has broad application prospects in aerospace, integrated circuits, and optical engineering due to its excellent mechanical properties, high thermal stability, and chemical resistance. Ultra-precision fly-cutting (UPFC) is a promising advanced technique for machining PI microstructures. However, few studies on the UPFC of PI materials are reported. In this study, the machining principle of UPFC is analyzed, and a comparative study of different processing strategies is conducted. The experimental results demonstrate that the climb cutting strategy is more suitable for PI microstructure machining, which can significantly reduce burr formation and achieve lower surface roughness. The theoretical models describing tool motion and predicting maximum chip thickness in UPFC are established, and the predicted chip thickness is consistent with the experimental results. Moreover, the influence of process parameters on the surface morphology and dimensional accuracy of microstructures is assessed through a series of experiments. The results indicate that cutting depth and step-over are the dominant factors influencing dimensional accuracy and surface roughness. Furthermore, the cutting force during UPFC is extremely small, only in the range of millinewtons (mN). In addition, the cutting force in the feed direction exhibits a high sensitivity to variations in process parameters compared to other directional components. This study provides theoretical guidance for the establishment of a theoretical model and the selection of UPFC process parameters for fabricating PI microstructures.