Research on surface generation in the ultra-precision parallel grinding of curved surfaces

Ultra-precision parallel grinding has been widely used in the fabrication of various complex curved surfaces for the advanced optical components with high precision and smoothness. In comparison with the machining of flat and spheric surfaces, in grinding of the curved surfaces, the concavity-convexity and local curvature of the workpiece change continuously along the wheel path, which imposes nonuniform scallop height generation. In this paper, three types of sinusoidal wave surface were ground and the influence of curvature on scallop height generation was studied. It is found that the scallop height has a close relationship with the curvature feature of the workpiece and the scallop height is relatively small in the area with relatively gentle curvature, however, for the area with larger curvature, the scallop height of the machined surface increased both for concave and convex surface regions, especially for the concave area, which further increases the scallop height of sine profile. The results show that changes in curvature can significantly cause uneven scallop height distribution for the grinding of curved surfaces due to the different wheel-location points between two adjacent tool loci at the same angular position in ultra-precision parallel grinding.