Investigation of the Geometrical Deviation in Injection Molding of Ultraprecision Optical Lenses

With rapid development of smartphones, performance requirements for injection molded ultraprecision optical lenses have become increasingly stringent. However, current research remains inadequate, particularly in elucidating the correlation between process parameters and lenses geometrical deviation. This study investigates the molding process of an ultraprecision aspheric optical lens, which feature a thickness of only 0.815 mm. Effects of key process parameters (injection velocity, packing pressure, back pressure and melt temperature) on geometrical deviation PV of the lenses were systematically studied. Notably, due to relatively small volume of lenses, packing pressure cannot be effectively transmitted to the cavity through the runner system, thus exhibiting limited influence compared to other parameters, which differs significantly from that in conventional molding. The geometrical deviation is unevenly distributed across the lenses and is strongly correlated with the part mass. A 2.6% increase in mass was found to reduce convex surface deviation by 74.8%, but simultaneously caused a 211.1% increase in concave surface deviation. These findings validate the feasibility of controlling geometrical deviation through part mass adjustment, providing important guidance for optimizing process parameters in manufacturing and improving product quality of ultraprecision optical lenses injection molding.