Investigation Of Several Key Technologies In Precision Glass Molding

In the last twenty years,precision glass molding(PGM)has been developed rapidly and studied widely for its advantages of high volume,low cost,environmental friendliness and nearly net-shape.However,due to temperature and pressure influence during the molding process,some defects could be introduced,such as profile deviation,residual stress and refractive index drop,which would affect the optical performance of molded lens.In order to investigate the influence of PGM process to molded lens,studies have been made on a self-developed PGM experimental machine.Temperature distribution in glass preform during the PGM process has been studied systematically by experiments and numerical simulations.Meanwhile,simulation research has been conducted thoroughly on wafer based micro lens array in the PGM process.The design and manufacturing of PGM experimental machine is not only the basis of the whole study,but also the prerequisite of subsequent experiments and simulations.Based on the available processing technology of our lab and research of current commercial and experimental PGM machines,technical requirements are put forward and the self-developed PGM experimental machine can be divided into four parts conceptually,namely molding module,thermal module,vacuum module and control module.Among these modules,the structural designs of mold assemblies and vacuum module are expounded.Besides,the control module can be made up of temperature control system and motion control system,and their partial and final integrated design of hardware and PC software are discussed.Temperature control experiments are conducted on the central thermal furnace of PGM experimental machine to investigate temperature distribution of glass preform in PGM process.To simulate this temperature control process,a PID control method is introduced to the numerical simulation software FLUENT,and its feasibility is validated by comparing the numerical results with experimental data.By importing the simulated temperature distribution data from FLUENT to ABAQUS,the whole PGM process with ununiform initial temperature distribution is simulated and its influence to the molded lens is studied.Using the simulated temperature distribution,effects of the structure of PGM machine,relative position between glass preform and mold assemblies and temperature control mode are investigated,and a two-point control method is proposed to improve the temperature uniformity of glass preform.Lastly,simulation research of temperature distribution and PGM process for wafer based micro lens array model is performed.Temperature gradient of glass wafer is along radius direction from the simulation results.By making some optimization to the furnace's structure,the temperature gradient is reduced effectively.Using the submodel technique in ABAQUS,it's able to conduct a 3D simulation of PGM process for the whole glass wafer as well as partial single micro lens.Based on the simulation results,effects of PGM process parameters,such as molding pressure in molding stage,holding pressure and cooling speed in annealing stage,cooling speed in rapid cooling stage,on the residual stress of glass wafer,sag height deviation of molded micro lens and pitch error of lens array are studied thoroughly.