A Systematic Optimization Method for Plastic Injection Molding Operational Parameters

Abstract

This paper presents an integrated optimization method to find the optimized operational parameters in Plastic Injection Molding (PIM), such as flow rate, melt temperature, mold temperature, pressure holding time and packing pressure that will minimize the shrinkage under the constraints of injection pressure and cooling time. Design of Experiments (DOE) is used to reduce the computational cost for simulations. Furthermore, the possibility value (P-value) is adopted to identify the significant factors among all design variables with respect to each functions. Monotonicity Analysis is then employed to detect the active constraints and to reduce the complexity of the original optimization problem so that the problem can be easily solved by a simple regression. Finally, the responses obtained by the simulation with the optimized operational parameters are used to validate our solutions. One design example is presented in this paper. For this example, twenty-five initial samples are evaluated using Solidworks Plastics based on the orthogonal array from the DOE with five variables. There are two constraints on injection pressure and cooling time. P-value shows that packing pressure is not a significant factor for shrinkage and two constraints in the example, then it can be moved out in later optimization. The exact value of flow rate and pressure holding time can be found out by Monotonicity Analysis. Finally, by solving the regression equations with melt temperature and mold temperature, the optimal parameters combination will be solved. Using the optimized parameters in simulation, the shrinkage for the example is 0.3950 mm, the shrinkage result is smaller than that in initial samples which can satisfy the constraints.