Development of a flexible and reliable numerical simulation for glass molding process

In the last two decades, precision glass molding is gradually becoming a competitive hot-replicating manufacturing technology for precision glass optical components such as aspherical lenses, lens arrays and freeform lenses. Due to thermal shrinkage of glass material during the cooling process, form error occurs on glass optics. In order to avoid the time-consuming and cost-intensive compensation iteration based solely on experiments, a numerical process simulation was developed at Fraunhofer IPT using commercial Finite Element Method (FEM) software ANSYS to predict the form error on the molded glass lenses even before the initial mold manufacturing. The developed process simulation consists of: a thermal model predicting the actual temperature distribution and a mechanical model to predict the viscoelastic deformation and thermal shrinkage ofthe molded glass lens. Previous results based on specific molding experiments proved that the developed process simulation is capable of predicting the form error and possesses a prediction accuracy of 2 micron. To expand the usage and improve the flexibility of the process simulation method, two different molding systems and popular molding experiments were analyzed in this paper and experiments were conducted to improve the simulation model and thus the prediction accuracy. With the improved models, the modularized simulation tool introduced in this work can predict form accuracy with high reliability under different molding conditions.