Numerical Simulation of Compression Molding of Aspherical Glass Lenses

Abstract

Articles you may be interested inAnalysis of different compression-molding techniques regarding the quality of optical lenses Abstract. Compression molding has become a viable manufacturing process for medium to high volume production of aspherical glass lenses. The lack of fundamental understanding of the process and other technical issues ranging from thermal shrinkage to mold coating wear and long molding cycles have made this process unsuitable for industrial applications. In this research, the various stages of the lens molding process have been modeled to understand the effect of different molding parameters to the final lens quality (geometry). 2-D axisymmetric simulations of the glass molding process have been performed using a commercial Finite Element Method (FEM) code. Glass has been modeled as a Newtonian fluid and temperature dependent viscosity and the heat transfer at the glass mold interface have also been taken into consideration. One of the main objectives of this research was to include the effect of viscoelasticity (time dependent response of glass to mechanical load), into the simulation model. A limited number of experiments were also performed and a comparison of the predicted results has been made with the experimental data. Although the predicted results seem to be in qualitative agreement with the experimental data, further research needs to be performed on viscoelasticity, structural relaxation (time dependent response of glass to change in temperature), and non-Newtonian behavior of glass at high stress levels, in order to make FEM a more effective tool for process analysis and optimization.

Multi-objective optimization of glass multi-station bending machining for smartphone curved screen

“…However, it is difficult to measure the relevant parameters. Like previous studies [19,20], glass thermal conductivity and specific heat are regarded as constants in this study. Therefore, the control equation of heat conduction for glass material is provided by Eq.…”

“…The results showed that the maximum stress decreases with the increase in molding temperature and increases with the increase in molding rate and friction coefficient. Jain et al [19,20] established a two-dimensional analytical heat transfer model of glass cylinder, taking into account the transient heat transfer at the edge of mold, and investigated the effects of different parameter settings (molding temperature, molding rate and cooling rate) on the quality of final product. It was found that there is a response relationship between residual stress and process parameters.…”

Investigation of the refractive index distribution in precision compression glass molding by use of 3D tomography

“…In the past few years, some work has been performed toward the development of the compression molding method for making glass lenses. Specifically, these efforts included predicting the profile of the glass lens [4], modeling group refractive index change [5], residual stresses [6,7] and studying thermal expansion of the mold and mold life during glass molding [7]. However, there are still quite a few challenges involved in this new method, and the refractive index variation in a molded glass lens is one of these challenges.…”