Experimental and simulation study on the optimum of the geometrical quality of bi-convex and bi-concave lenses produced by injection molding process
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Investigation of the geometric and optical quality of polymer lenses in the injection molding process is costly and time-consuming. So, reducing the cost of inspection while ensuring the optical quality of the lenses after production is considered in this study. The geometric quality of bi-convex and bi-concave spherical lenses is achieved by monitoring the pressure and temperature profile inside the mold cavity during injection. Regarding the priority of the effect of the geometric parameters, average volumetric shrinkage and warpage are the best parameters for consideration. The results show that the most important effective injection molding process parameters in lens molding are packing time, packing pressure, melt temperature and mold temperature. According to the experimental results, the average amounts of PV for the two surfaces of the bi-convex lens in the optimum level are 7.7 μ and 7.9 μ and for the bi-concave lens are 8.8 μ and 8.1 μ. In addition, the geometric quality of a lens is better when the trend of slope of the pressure graph is lowered to zero and should not be reduced suddenly for all three sensors locations.
KeywordsAverage volumetric shrinkage Warpage Spherical lens Injection molding Peak-to-valley Mold cavity pressure–temperature
Special thanks to Professor Mahmoud Masoumi, the faculty of Chemical Engineering Department, and Professor Mehdi Ranjbar, the faculty of Physics Department for their valuable comments. Also thanks to the staff of the Polymer and Glass Processing laboratory in the Mechanical Engineering Department, Isfahan University of Technology.
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