FEM simulation and analysis on molding process of infrared aspheric lenses

Glass molding press (GMP) is a kind of mass production method to manufacture infrared aspheric lenses made from chalcogenide. However, it´s hard to determine the molding parameters during the GMP process because the lens forming is conducted under the high-temperature conditions. In this paper, the finite element method (FEM) is used to simulate the GMP process based on the general Maxwell viscoelastic model and thermo-rheologically simple property. During the simulation, 2-D axisymmetric FEM model is constructed according to the different pressing velocities and friction coefficients, which change from 0.01mm/s to 0.5mm/s and from 0.01 to 0.2, respectively. To improve the simulation accuracy, the heating and pressing steps are separate and the heated result is taken as the pre-state of pressing step. The final results show that the best molding conditions are 0.1~0.2mm/s in velocity and 0.1~0.15 in friction coefficient for the infrared aspheric lenses made from chalcogenide of Ge₃₃As₁₂Se₅₅.