Dynamic Visualization Experimental Study Of Internal Stress On The Optical Products

With the development of aerospace, biomedical and other high-tech, precision injection molding technology are becoming increasingly widespread, it also made a higher requirements to precision injection molding technology.Residual stress is a common molding defect in injection molding technology. It not only affects the appearance of quality products, but also seriously affects the product's optical, electrical, mechanical properties. In the injection molding process, residual stress includs thermal residual stress and flow residual stress. Because the thermal residual stress is much larger than the flow residual stress, the flow residual stress is usually ignored in academic research,or used a fixed parameters.But to optical products, the flow residual stress seriously affects light transmission. Especially to some sophisticated lens and glass lens, the flow residual stress became a lethal threat.In this paper,with the help of the photoelastic and light transmission visualization device, we developed a dynamic internal residual stress visualization system.And by using this system,we found the distribution and formation mechanism of the flow residual stress.By comparing the difference between birefringence stripes in different process parameters and mold structure products, and using polarizing microscope to calculate the flow residual stress and using the software of moldex3D to simulate the shear rate, temperature field, pressure field of the melt, we conclude that the injection pressure, packing pressure mold structure on the flow residual stress impact the flow residual stress of the products. The process guidelines is provided for the optical-grade products in injection molding process.In this paper, with precision injection molding systems of visualization experiments,we study high-temperature melt flow behavior in three typical rectangular cavities and get formation mechanism of the weld line and jetting phenomenon.By analyzing connection between mold design parameters and flow behavior,we obtained the means to solve the weld line and jetting phenomenon.