Tribological wear analysis and numerical lifetime prediction of glassy carbon tools in fused silica molding

Abstract Precision Glass Molding (PGM) is currently the standard manufacturing process for medium-lot-size fabrication of complex shaped, high-quality lenses. During each molding cycle in PGM, the molding tools experience thermal and mechanical loads. Degradation mechanisms caused by these loads limit the molding tool life. Therefore, acquiring a deeper knowledge of the fundamental degradation mechanisms of molding tool surfaces is of high-interest. In this work, the tribological wear mechanisms of the surfaces of glassy carbon tools used for fused silica molding were investigated. Both an experimental study and a finite element method (FEM) simulation are presented, and their results were correlated. In the experimental study, the progressive wear process on glassy carbons surfaces was investigated using scanning electron microscopy (SEM). In addition, atomic force microscope (AFM) measurements of the sizes of surface defects such as notches were analyzed. Experimental results were compared with a FEM simulation of the tensile stresses and sliding velocity that arise during each fused silica molding cycle. Using this approach, the dimensions of wear can be calculated after any given number of molding cycles and the lifetime of the molding tools can be predicted.