Chen Jian-Yu, Liu Chun-Ying, Huang Ming-Shyan
Bachelor's Program of Precision System Design, Feng Chia University, 100, Wenhwa Rd., Seatwen, Taichung City 40724, Taiwan.
Department of Mechatronics Engineering, National Kaohsiung University of Science and Technology, 1 University Rd., Yanchao Dist., Kaohsiung City 824, Taiwan.
Polymers (Basel). 2019 Jul 9;11(7):1168. doi: 10.3390/polym11071168.
Filling-to-packing switchover (also called V/P switchover) is critical for assuring injection molding quality. An improper V/P switchover setting may result in various defects of injection-molded parts, such as excessive residual stress, flash, short shot, and warpage, etc. To enhance a consistent molding quality, recent V/P switchover approaches adopt cavity pressure profiles requiring sensors embedded in mold cavities, which is invasive to mold cavities and more expensive. Instead of using cavity pressure sensors, by working with the most popular screw position switchover control, this study hereby proposes a novel approach of tuning V/P switchover timing using a tie-bar elongation profile. In this investigation, a dumbbell testing specimen mold is applied to verify the feasibility of the method proposed. The results show that the mold filling and packing stages can be observed along the tie-bar elongation profile, detected by mounting strain gauges on the tie bars. Also, the characteristics of the cavity pressure are similar to those of the tie-bar elongation profile under a proper clamping force condition. Moreover, the varying process parameter settings which include injection speed, V/P switchover point, and holding pressure, can be reflected in these profiles. By extracting their characteristics, the application of the V/P switchover is proved to be realistic. This research conducted an experiment to verify the proposed V/P switchover decision method based on the tie-bar elongation profile. The result showed that the fluctuation of the part's weight corresponding to a slight change of the barrel's temperature from 210 °C to 215 °C can be successfully controlled with this method. Besides, the maximum clamping force increment extracted from the tie-bar elongation profile was found to be a good indicator for online monitoring of the reground material variation.
充模到保压切换（也称为V/P切换）对于确保注塑成型质量至关重要。不当的V/P切换设置可能会导致注塑成型零件出现各种缺陷，如残余应力过大、飞边、缺料和翘曲等。为了提高成型质量的一致性，最近的V/P切换方法采用了需要在模腔内嵌入传感器的型腔压力曲线，但这对模腔具有侵入性且成本更高。本研究不使用型腔压力传感器，而是结合最常用的螺杆位置切换控制，提出了一种利用拉杆伸长曲线来调整V/P切换时机的新方法。在这项研究中，应用哑铃形测试样品模具来验证所提出方法的可行性。结果表明，通过在拉杆上安装应变片进行检测，可以沿着拉杆伸长曲线观察到模具的充模和保压阶段。此外，在适当的合模力条件下，型腔压力的特征与拉杆伸长曲线的特征相似。而且，包括注射速度、V/P切换点和保压压力在内的不同工艺参数设置都可以在这些曲线中体现出来。通过提取它们的特征，证明了V/P切换的应用是切实可行的。本研究进行了实验，以验证基于拉杆伸长曲线提出的V/P切换决策方法。结果表明，使用该方法可以成功控制料筒温度从210℃轻微变化到215℃时零件重量的波动。此外，从拉杆伸长曲线中提取的最大合模力增量被发现是在线监测回料变化的一个良好指标。
