Simulation and experimental research of tool path planning on profile and surface generation of aspherical-cylindrical lens array by ultra-precision envelope grinding

Abstract

Profile accuracy and surface quality of microstructural array mold generated by ultra-precision machining are the premise of precision glass molding technology. Most optical applications of microstructural array mold need to obtain microstructures with sub-micron profile accuracy and nanoscale surface roughness. However, the structural characteristics of grinding wheel and array leads to the complexities of surface generation in envelope grinding. Experimental verification is time-consuming and laborious. In this paper, a multi-scale model is proposed to predict the surface topography of micro-aspherical-cylindrical structural array (MACSA) mold ground by different tool paths. Firstly, the ultrathin grinding wheel is reconstructed by considering the distribution characteristics of abrasive grains and the complex wheel profile. In this process, the grain distribution characteristics of the reconstructed grinding wheel are obtained by using the Johnson transformation the inverse Johnson transformation method. Then, a comprehensive model is established to understand the mechanism of the generation of the MACSA surface, which considers the wheel topography, the kinematics model of abrasive grains and the complex geometric conditions between tool and local surface profile in envelope grinding. The surface morphologies of MACSA obtained by simulation and experiment are coincident with each other very well. The simulation model is further verified by comparing the power spectral density (PSD) of the experimental and simulated surfaces. Based on the simulation and the experimental results, the effect of three tool path planning methods (constant step, constant arc length and constant scallop-height) on surface uniformity and profile accuracy is investigated to obtain a more uniform microstructural surface.