Research on arc-shaped wheel wear and error compensation in arc envelope grinding

Abstract

Arc envelope grinding method (AEGM) is commonly used for grinding large-aperture mirrors and greatly increases the wheel life and the machining accuracy. As the grinding point shifts on the arc-shaped wheel, a three-axis machine tool is qualified to manufacture aspherical or off-axis surfaces. However, compared with traditional aspherical grinding with a rotary table, grinding process on T3-configuration machine tools is more complicated. The grinding point varies in both latitude and longitude directions on the wheel. In this paper, a new algorithm for wear simulation based on 3D wheel-workpiece contact area is proposed to better understand the wear process in grinding aspherical surface. The resin-bonded diamond wheel was trued by GC (green silicon carbon) wheel. In order to get the grinding ratio, the wear of the wheel profile was measured after grinding a flat SiC-ceramic surface several times. Then, the wheel profile error was compensated first by analyzing the wheel-workpiece contact status. Gaussian process (GP) regression method was used to fit the form error and eliminate both noise and high-frequency waves in the measured data. The residual error was further compensated, and the compensation value was calculated by GP model. The proposed error compensation methods were verified on a three-axis grinder, and RMS value was successfully reduced by 37%.