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Figure 5 displays the variation of the volumetric shrinkage with time in the Moldflow analyses. The simulation results of the volumetric shrinkage shown in Fig. 5 are selected from 27
Fig. 5 The results of volumetric shrinkage with time for FE analyses of 4, 10, 16, and 22
Fig. 6 The change of the clamp force with the time
Fig. 7 The change of the recommended ram speed with the stroke
FE analyses equally. From the results shown in Fig. 5, it can be
Fig. 8 The measurement of experiments
Here, Lcavity is the length of the mold cavity; Lproduct is the target length of the molded plastic part of the DVD-ROM cover. The values of Lproduct for the DVD-ROM cover were accurately measured by a profile control instrument (T-S INDUSTRIES Inc, St. James, MN).
seen that the values of the volumetric shrinkage versus time exhibit an unstable trend for FE analyses of 4, 10, 16, and 22. Furthermore, these analyses demonstrate a general variation for
Shrinkage ð%Þ¼
.. Lcavity — Lproduct.
Lcavity
.
m 100
ðEq 19Þ
all of the 27 FE analyses.
Figure 6 demonstrates the change of the clamp force in the plastic injection machine versus time for the plastic injection of the DVD-ROM cover. It can also be inferred that the clamp force increases regularly as the time increases to 3 s and after 3 s, it remains constant. Figure 7 indicates the change of the recommended ram speed with the stroke, and it can be emphasized that the recommended ram speed increases regu- larly as the stroke increases and then decreases continuously.
5. The Measurement of Experiments
The experiments for four plastic injection moldings of the plastic part of the DVD-ROM cover and their measurements, as shown in Fig. 8, were carried out to control the simulated values obtained from the developed regression model with FE analyses obtained from Moldflow. The four injection moldings were taken from ten plastic molding experiments (4 parts per
10 experiments). Five measurements were performed for a total of 40 experiments and each measurement was repeated at least three times. The formulation written in Eq 19 was utilized to control the simulated values with the FE analyses.
Table 9 shows the results of the measured values, the simu- lated values, and FE analyses. In Table 9, it can be seen that the measured values match very well with the simulated val- ues and FE analyses. The APE was found to be 2.887% for the regression model (the simulated values) and 0.972% for the FE analyses.
6. Conclusion
In this study, an effective regression model was developed to determine the mathematical relationship between the plastic injection molding parameters and the volumetric shrinkage of the DVD-ROM cover. The orthogonal array of Taguchi (L27) designed by the process parameters of the mold temperature, melt temperature, injection pressure, injection time, and cooling time was created to run 27 FE analyses in Moldflow simulation program. ANOVA analysis was performed to identify the most significant process parameters and to check the adequacy of the regression model developed on the shrinkage. Based on the first-order and the second-order models for the shrinkage, the maximum error (ME) was found to be 3.895 and 3.994 %, respectively. Finally, the experiments consisting of four plastic
Table 9 The results of the experiments
The errors (APE %)
Experiment no Measured values