High flatness polishing of rectangular glass materials (2nd Report) generation of a center-axisymmetric shape by grinding and compensation method of tool inclination for polishing simulation

High flatness and smoothness are required for an extremely large rectangular glass mask of about 1 m used for pattern transfer of liquid-crystal panels. However, it is difficult to polish rectangular plates with a rotary polishing machine. Therefore, a new simulation program for a rectangular workpiece has been developed. This paper describes the shapes that were non-symmetrical about the central axis generated by grinding, the method to change to a center-axisymmetric shape, the compensation method of tool inclination for simulating polishing, and a comparison between experimental and simulated results for a rectangular workpiece. It was shown that a center-axisymmetric shape can be obtained by grinding at an infeed rate of less than 1 um/min after dressing to decrease the grinding force, and that the relationships between removal rate and both relative velocity and pressure are proportional for quartz materials. The simulation results agreed with the experimental results under various conditions of tool positions, oscillation ranges and tool diameters by using the new compensation method of tool inclination.