Quantitative study of shrinkage and warpage behavior for microcellular and conventional injection molding

Abstract

This research investigated the effects of processing conditions on the shrinkage and warpage (S&W) behavior of a box‐shaped, polypropylene part using conventional and microcellular injection molding. Two sets of 26‐1 fractional factorial design of experiments (DOE) were employed to perform the experiments and proper statistical theory was used to analyze the data. After the injection molding process reached steady state, molded samples were collected and measured using an optical coordinate measuring machine (OCMM), which had been evaluated using a proper R&R (repeatability and reproducibility) measurement study. By analyzing the statistically significant main and two‐factor interaction effects, the results show that the supercritical fluid (SCF) content (nitrogen in this case, in terms of SCF dosage time) and the injection speed affect the S&W of microcellular injection molded parts the most, whereas pack/hold pressure and pack/hold time have the most significant effect on the S&W of conventional injection molded parts. Also, this study quantitatively showed that, within the processing range studied, a reduction in the S&W could be achieved with the microcellular injection molding process. POLYM. ENG. SCI., 45:1408–1418, 2005. © 2005 Society of Plastics Engineers

Single and Multi Objective Optimization for Injection Molding Using Numerical Simulation with Surrogate Models and Genetic Algorithms

“…It demonstrates that the trained SVR surrogate models, which require a reasonably small amount of computational resources, possess good predictive capability for substituting the complete simulations after they are properly trained. It is also found that the minimum S&W corresponding to the optimal process conditions determined by the SVR models is smaller than the minimal S&W predicted by the experimental regression [20]. This is because the surrogate models established here are more flexible in determining the optimal conditions; and these optima need not to be restricted to the fixed levels as used in conventional factorial DOE for actual molding experiments.…”

“…Table 3 also lists the optimal process conditions obtained from experimental regression for minimizing the S&W, as reported in [20]. From the comparison, the difference between the results from the surrogate models and the simulation is quite small (5.57 %), which suggests that the trained surrogate models can reproduce the simulation results reasonably well.…”

“…Then it will be applied to optimize six sets of process conditions in order to minimize the averaged S&W. The optimization results will be compared with experimental data to demonstrate the performance and capabilities of the optimization approach. Details of the experiment setup, procedure, and result analysis can be found in [20]. By defining ÀX j j; þX j j; ÀY j j; and þY j j as the absolute values of the S&W deviations in the four directions shown in Fig.…”

“…The simulation program was executed using the same process conditions (cf. Table 1) according to the fractional factorial DOE used for the 32 molding trials [20]. The comparison of the simulation results and the experiment data are tabulated in Table 2 Fig.…”

Thermoviscoelastic Behavior of Film‐Insert‐Molded Parts Prepared under Various Processing Conditions

“…Heat transfer perpendicular to the cavity wall can be retarded because the film is attached on one side of the cavity wall and two different polymers are used as the film and substrate. [5] Many studies have been carried out to investigate the effects of processing conditions on the warpage and residual stress distribution of injection molded parts without any inserted film; [6][7][8][9][10][11][12][13][14][15][16][17] however, investigations of the FIM process have rarely been reported. It is essential to understand the residual stress distribution and to predict the viscoelastic deformation of the molded part for the practical application of FIM to industrial end-user products.…”