Study on the micro-milling of optical microstructure with the assist of the workpiece vibration

Precision micro-milling technology is an important method to machine microstructure. However, precision micro-milling cutting system has relatively low stiffness. This will directly lead to the deterioration of the machining quality and thus cannot fulfill the high accuracy requirements of parts. Vibration assisted machining has produced a good effect in high stiffness cutting system using non-rotary tool. In this paper, the workpiece vibration assisted method is adopted instead, to improve the processing condition and the practical machining quality. The vibration assisted system is a vibration worktable driven by a piezoelectric ceramic actuator. In order to study the influence of vibration frequency on the machining quality, a non-resonant vibration assisted worktable is designed to realize the adjustment of vibration frequency. Orthogonal experiment is conducted to study the influence of three factors including the feed rate, vibration frequency and amplitude on the machining quality. The ranges of these factors are 1 μm/z to 5 μm/z, 500 Hz to 4000 Hz, and 0.5 μm to 2 μm, respectively. The experimental results show that, in the extent of the process parameters, form error (P-V value) and roughness (Ra) decrease as the vibration frequency increases, while the vibration amplitude contributes to good surface quality only in a proper range. Too low amplitude has little influence on the machining quality, and too high amplitude may even worsen the quality. And after the vibration assisted method is applied, the PV value and Ra can be reduced by approximately 27% and 42%.