Numerical and experimental study of thickness effect on deflection of glass plate in elastic deformation machining method

摘要

Elastic deformation machining is a fabrication method that uses the elastic deformation properties of materials to make a desired surface form. Coupled with plane lapping machining process, the fabrication method is suitable for machining large aspheric surfaces. In this method, the workpiece is deformed under load and the bottom side of the workpiece is lapped to a flat surface. When the load is released, the bottom surface of the workpiece will be shaped into an aspheric shape. However, the thickness of workpiece is changed in the lapping process while the load remains unchanged. Therefore, the form accuracy of workpiece will increase with desired form surface. The effect of vacuum pressure on deflection of glass plate which changed thickness in lapping process is predicted in this study based on the numerical finite element analysis (FEA) results to determine vacuum pressure values which correspond with changed thickness of workpiece in the experimental process. The study indicates that, the effect of changed thickness on profile accuracy of workpiece in the elastic deformation machining is significant. The form accuracy of workpiece is improved from 62 μm to 1.6 μm which vacuum pressure is reduced from 50 kPa to 42 kPa in the experimental process.