Thermo Mechanical Modeling and Analysis of Precision Glass Molding Process

In recent decades, the demand for ultra-precise optical components with intricate geometric profiles has increased dramatically. Traditionally, polymer-based lenses have dominated the industry, but due to the benefits of using glass components, the demand for ultra-precision glass aspherical components has been rising consistently. When producing aspherical glass components, however, conventional manufacturing processes become time-consuming and expensive. Precision glass molding (PGM) technology offers an alternate method of production for aspherical glass lenses and irregular optical products. Compared to the conventional manufacturing process, it has the advantages of high forming accuracy, short manufacturing cycles, low cost, and high-volume production. However, the process has a few drawbacks, such as lens profile deviations, stress birefringence, etc. Before the glass molding process can be a viable option for mass-producing optical components, these drawbacks must be addressed. As such, a coupled thermo-mechanical finite element model is developed in this dissertation to simulate the precision glass molding process on two distinct glass varieties, D-ZK3 (CDGM) and P-SK57 (Schott). A novel testing method is developed to precisely characterize the viscoelasticity of the glass material. It is demonstrated that the obtained material parameters accurately depict the experimental data at various molding temperatures. In addition, the material testing experiments are designed to be implemented on a glass molding machine, simplifying the development and characterization of different moldable glass materials. The obtained material parameters are implemented in the finite element model to predict the profile deviation in the molded lens and compared with experimental results. A mold compensation technique is used to correct the mold profiles. The lens molded on the modified molds is shown in fall within the tolerance specifications. However, it was observed that the process parameters used during the molding process have an influence on the deviations and the stresses in the molded lens. Therefore, it is essential to optimize the molding process prior to implementing mold compensation techniques. The developed numerical model is used to analyze the impact of various process stages and parameters on the optical quality of molded lenses. Based on the observations, a modified molding process was developed which is shown to minimize the influence of the molding parameters on the deviations and the residual stress. In addition, it was demonstrated that the modified manufacturing process reduces the total cycle time for producing a glass lens of comparable optical quality by more than 50%, reducing the manufacturing cost of a molded glass lens.