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Glass molding has become a key replication-based technology to satisfy intensively growing demands of complex precision optics in the today's photonic market. However, the state-of-The-Art replicative technologies are still limited, mainly due to their insufficiency to meet the requirements of mass production. This paper introduces a newly developed nonisothermal glass molding in which a complex-shaped optic is produced in a very short process cycle. The innovative molding technology promises a cost-efficient production because of increased mold lifetime, less energy consumption, and high throughput from a fast process chain. At the early stage of the process development, the research focuses on an integration of finite element simulation into the process chain to reduce time and labor-intensive cost. By virtue of numerical modeling, defects including chill ripples and glass sticking in the nonisothermal molding process can be predicted and the consequent effects are avoided

Precision glass molding is an efficient near net shape fabrication method for high volume production of aspherical optical glass components. Up until now, the mold manufacturing is still the most cost-and time-consuming process partly due to the fact that the shrinkage error of glass has to be compensated for by means of multiple molding trials and mold modifications (this process is sometimes called mold iteration). The main reason for shrinkage is the different thermal expansions of mold and glass materials during forming and cooling, many other factors such as uneven cooling speed and stress relaxation affect molding process and thus lead to complex form deviation in final geometry. In this paper, an efficient mold manufacturing process with integrated numerical simulation is presented in the form of a case study of an industrial molding example. Taking into account the shrinkage error predicted by process simulation, revised molds are manufactured directly with compensated design. After molding test with the compensated molds, the surface figure of the molded glass lenses was in good agreement with the desired shape within plus/minus 1 micrometer, which matched the original accuracy requirement and no further mold compensation was needed. Based on the result of this work, it is clear that numerical simulation can be used as an efficient tool to predict the final geometrical shape of precision molded glass components, which leads to an efficient mold manufacturing with lower production cost and a shorter cycle time

During fabrication of glass lens by precision glass molding (PGM), residual stresses are setup, which adversely affect the optical performance of lens. Residual stresses can be obtained by measuring the residual birefringence. Numerical simulation is used in the industry to optimize the manufacturing process. Material properties of glass, contact conductance and friction coefficient at the glass-mold interface are important parameters needed for simulations. In literature, these values are usually assumed without enough experimental justifications. Here, the viscoelastic thermo-rheological simple (TRS) behavior of glass is experimentally characterized by the four-point bending test. Contact conductance and friction coefficient at P-SK57™ glass and Pt-Ir coated WC mold interface are experimentally measured. A plano-convex lens of P-SK57™ glass is fabricated by PGM for two different cooling rates and whole field birefringence of the finished lens is measured by digital photoelasticity. The fabrication process is simulated using finite element method. The simulation is validated, for different stages of PGM process, by comparing the load acting on the mold and displacement of the molds. At the end of the process, the birefringence distribution is compared with the experimental data. A novel plotting scheme is developed for computing birefringence from FE simulation for any shape of lens