Three-dimensional numerical analysis of injection-compression molding process

Abstract

Injection-compression molding (ICM) process, combining conventional injection molding (CIM) process with compression molding, has been widely used in the manufacturing of optical media and optical lenses. Most of previous numerical studies regarding ICM process employ the Hele-Shaw approximation, which is appropriate for thin cavity geometry only. This work presents a three-dimensional numerical analysis system using a stabilized finite element method (FEM) and an arbitrary Lagrangian-Eulerian (ALE) method for more rigorous modeling and simulation of ICM process of three-dimensional geometry. The developed system is verified by comparing the results with existing experimental data as well as simulation data obtained from commercial software. Then, the system is adopted for simulations of ICM process of an optical lens, which is a practical example of three-dimensional geometry. According to the simulation results, three-dimensional flow characteristics are found to be significant especially during compression stage because of the squeezing nature of the flow. The results are then compared with those of CIM process, showing that ICM process results in reduced and more uniform distributions of the generalized shear rate and shear stress of the final part. Basic parametric studies are also carried out to understand effects of processing conditions, such as compression velocity and compression gap. POLYM. ENG. SCI., 52:901-911, 2011. (C) 2011 Society of Plastics Engineers