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.
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