Glass Molding Process (GMP) is an effective method for producing precise optical elements such as lenses. This simulation study aimed to predict the distribution of temperature and stress within a lens during a multi-stage cooling process of GMP. To develop an accurate simulation model including molds and lens, thermal contact conductance and boundary conditions were determined by analyzing experimental and simulation results. The developed model was used to investigate changes in temperature and maximum principal stress within the lens, considering variations in cooling time, speed, and method at each cooling stage. Simulation results indicated that trends of maximum temperature difference and maximum principal stress within the lens were consistent over time. Results also showed that the maximum principal stress inside the lens increased significantly with additional cooling after uneven temperature distribution caused by a relatively short cooling time. Compared to simulation results of the cooling process involving contact only with bottom surface of the mold, contact cooling with both top and bottom surfaces showed decreased residual stress at the end of cooling and maximum temperature difference within the lens. However, the maximum principal stress could be higher during the cooling process involving both surfaces.

Vitreous carbon (VC) is an excellent material for glass molding due to its high hot hardness and low adhesion to glass materials. As a low-cost VC micro/nano mold fabrication method, carbonization of replicated Furan precursor has been investigated for various glass molded micro/nano optical and fluidic devices. One of the critical issues identified in the method is the substantial pyrolysis shrinkage (~22%) during the carbonization process. In this study, a method of minimizing pyrolysis shrinkage by adding VC powder to the initial Furan resin mixture was investigated. The mixing ratio of Furan resin, initiator, and ethanol was experimentally optimized for each VC powder mixing ratio, and the effects of the VC powder mixing ratio on the pyrolysis shrinkage of VC mold were examined. As the VC powder mixing ratio increased from 0% to 40%, we observed a reduction in the shrinkage ratio from 22.18% to 12.89% aligning closely with theoretical expectations.