为实现辊筒模具大面积微透镜阵列的高效率与高精度加工, 对微透镜阵列成形法的加工轨迹优化和进给轴伺服参数的优化方法进行了理论分析与实验研究。首先, 通过分析微透镜阵列的特征轮廓, 确定微透镜表面振纹的主要诱因为过渡台阶的突变;其次, 为使加工轨迹的二阶导数具有连续性, 提出采用三次样条插值与傅里叶级数拟合对加工轨迹进行分段优化设计; 最后, 在优化加工轨迹的基础上, 通过调整伺服系统的前馈参数, 改善了进给轴的响应能力, 减小了因驱动质量和阻尼而产生的跟踪误差。口径为800 μm、深度为26.7 μm的微透镜阵列的加工实验表明: 采用优化的刀具轨迹和伺服参数, 微透镜加工效率可以达到8 Hz, 进给轴跟踪误差小于300 nm, 并消除了微透镜阵列的表面振纹。微透镜单元口径尺寸精度为设计值的1.075%, 随机检测50组, 口径尺寸变化范围控制在2 μm内, 表明微透镜具有良好的尺寸一致性。实验结果表明, 加工轨迹的分段设计方法和伺服参数优化可有效抑制进给轴的振动, 改善了微透镜阵列表面质量。

In order to realize the high-efficiency and high-precision fabrication of micro-lens array in a large-sized drum lathe, a study on tool path fitting and servo parameter optimization for micro-lens machining with slow tool servo was presented theoretically and experimentally in this paper. The original trajectory characteristics of the micro-lens array were analyzed first, and the chatter marks on the micro-lens surface were caused by sharp points at the original machining trajectory. Secondly, a method was proposed to fit the machining trajectory of the transition section using cubic spline interpolation and Fourier series fitting in order to ensure the trajectory's continuity of the second derivative. Finally, the capability of dynamic response was improved by adjusting the servo parameters, so that the follow error (FE) of the feed axis caused by the inertia and damping effect was reduced with the optimization of machining trajectory. Machining experiments on micro-lens with diameter of 800 μm and depth of 26.7 μm were carried out. The results show that the homemade ultra-precision machine can fabricate eight micro-lenses per second with 300 nm FE, and the chatter marks of the micro-lens surface caused by sharp points are eliminated. The diameter error of micro-lens is 1.075% of the designed value. The fitting method has a good effect on the surface quality of micro-lens array.