4。5 Influence of injection molding parameters on cavity pressure

This section uses experiments changing one factor level at a time on eight control factors, as based on the optimal injection molding parameters, in order to discuss the influence of pa- rameters on the pressure profile and lens form accuracy。 The parameter setting levels were as shown in Table 5。 The pres- sure  profile during the  injection molding process   was

Time (sec)Time (sec)Time (sec)

(a) Cavity (b) Secondary runner (c) Tertiary runner

Fig。 9  Cavity pressure profiles with various injection pressure。 a Cavity。 b Secondary runner。 c Tertiary runner

(a) Cavity (b) Secondary runner (c) Tertiary runner

Fig。 10  Cavity pressure profiles with various switchover positions。 a Cavity。 b Secondary runner。 c Tertiary runner

recorded, and the form accuracy of the injected lens was measured in each experimental condition。 Figures 9, 10, 11,

12, 13, 14, 15, and 16 show the runner and cavity pressure profiles obtained by changing eight injection molding param- eters。 On each of the figures, the cavity pressure contours for different parameter levels are shown in diagram (a), whereas diagrams (b) and (c) show pressure contours for the secondary runner and tertiary runner, respectively。 The cavity pressure contours for Taguchi optimal parameters in diagrams (b) and

(c) were included for comparison。 Because of a variation in the injection machine, a slight change in cavity pressure contour at the Taguchi optimal parameters was observed for different experiments。 Moreover, in Fig。 16, the pressure contours at different packing times indicated that the pressure delay becomes more significant with increasing packing time。

The other five parameters also have a significant effect on the

the lens form accuracy。 In other words, when the temper- ature was 250 °C, there was a flash due to the very high melt temperature, and this condition was inapplicable。 The mold temperature and packing time significantly influ- enced the form accuracy of the lens, with results matching the above Taguchi experiment。 The changes in other pa- rameters slightly affected the form accuracy of the    lens。

Pearson’s correlation coefficient (r) is widely used to de- termine whether there is linear correlation between two con- tinuous variables [45]。 In this study, the correlation was used to identify the correlation between the pressure histories for different positions with parameter levels。 The correlation co- efficient is defined as:

摘要：注塑成型过程中的型腔压力与成型制品的质量密切相关，被用于生产过程监控和控制，来提高产品质量。然而，安装在型腔内的传感器使型腔内模塑产品有缺陷，降低了生产效率。鉴于此，本研究探讨在不同的流道中的熔体压力和型腔压力之间的相关性，并确定适当的浇口位置，让其中的流道压力代表型腔压力，以提高生产效率。首先，用田口方法获得合适的注塑成型参数组合，然后，实验是在这种情况下，来探讨流道和型腔压力历史曲线之间的差别。根据实验结果，成型的产品质量可以监测和控制通过在不同的流道位置安装传感器，并将型腔压力分布的最大值用作浇口位置。当位于二级流道内的压力传感器的顶部和流道外直径之间的距离大于模制产品的最大厚度，所获得的压力历史曲线接近型腔内压力。换言之，流道内的压力可以代表型腔压力。模具温度对注塑成型过程中的模具温度有着显著的影响，在注塑成型过程中，可以作为过程监控参数。此外，冷却阶段的型腔压力曲线与透镜的形状精度密切相关，是确定加工监控参数的关键。