Finite Element Analysis On Molding Process Of Glass Lens With Aspherical Concave-convex

Optical elements are playing an important role in the modern society.Opto-electronic devices for entertainment,communication,manufacturing and measurement are widely used,in which aspherical glass lens comes to be more eye-catching for its effective correction to image distortion,aberration,and coma;also the improvement of image quality and systematical identification,equipment structure simplification as well.Differ to conventional material removal techniques,glass molding process(GMP)has the advantages of high efficiency,low cost,and achievable mass production.It can be used directly without follow-up polishing processing.However,two challenges still be there in current practical production.Firstly,the large residual stress left in molded glass in GMP,which may cause crack or fracture on the surface,affecting optics properties and reducing service life;secondly,there is a forming error between the final shape and designed shape.In order to solve these problems,a numerical model of aspherical concave-convex glass lens by Msc.Marc finite element analysis program has been established for respective simulation calculation to residual stress of molded glass and forming error as well,and GMP experiment is supposed to verify the effectiveness of the simulation calculation.Single forming parameter will be changed later to research some features' effect on residual stress and forming error.The major researches as follows:1.Build four phases numerical models of heating,molding,annealing,cooling stages on the base of generalized Maxwell model to predict lens residual stress in the whole molding process.The result shows that residual stress is mainly focus on the inner side of bump surface;the largest residual stress is around the inflection point,and force on the concave surface is greater than that on the convex side.Residual stress in inner lens can be eliminated effectively during the annealing process.Take a residual stress test to the molded aspherical concave-convex glass lens in GMP experiment,and the result correlate with the prediction result,which proves the effectiveness of simulation.2.Build four phases numerical models of heating,molding,annealing,cooling on the base of generalized Maxwell model to predict lens residual stress in the whole molding process.The result shows that residual stress is mainly focus on the inner side of bump surface;the largest residual stress is around the inflection point,and force on the concave surface is greater than that on the convex side.Residual stress in inner lens can be eliminated effectively during the annealing process,and it comes to be a lower value when annealing finished.Take a residual stress test to the molded aspherical concave-convex glass lens in GMP experiment,and the result correlate with the prediction result,which proves the effectiveness of simulation calculation.3.Forming error is mainly shows in three aspects in analysis on GMP:1)Machining error on cavity surface in molding process;2)Distortion emerged when glass perform replicate thermal deflection mold profile in molding process;3)Lens structure relaxation in annealing period.Prediction of forming error that lens performed in GMP is on these basis mentioned above.The surface profile,from the finished aspherical concave-convex glass lens in experiment,the result correlate with the prediction result,proving it is in the feasibility for predicting lens forming error via numerical simulation.4.Single forming parameter will be changed later to research some features' effect on forming error.It is said that forming error increases with bigger molding rate,decreases as temperature goes up.However,higher temperature leads to larger deviation;error reduces when annealing rate,dwell pressure and friction coefficient gets down;and cooling rate,it it no obvious affect to forming error.