Abstract Due to its low cost and high efficiency, injection molding is used for the mass production of many plastic products nowadays. However, when processing low-viscosity plastic materials, i.e., materials with an excellent fluidity, an inappropriate setting of the clamping force often results in a poor appearance and dimensional accuracy of the final product. Thus, operators usually take the upper limit of the clamping force as a default in setting up the machine in an attempt to improve the quality of the molded parts. However, such an approach shortens the machine and mold life, increases the energy consumption, and leads to poor air venting. Consequently, more scientific methods for determining the clamping force setting are required. To meet this demand, the present study proposes a clamping force search methodology for determining the optimal clamping force setting of a hydraulic cylinder clamping injection molding machine in the processing of low-viscosity plastics such as thermoplastic polyurethane (TPU) and polypropylene (PP). Based on the characteristic extracted from the sensing tie-bar elongation profile under different clamping force settings, a regression analysis on these data points is implemented to seek for an optimal clamping force. The experimental results show that for an injection molding machine with a hydraulic cylinder clamping mechanism, the effect of the mold temperature on the clamping force is sufficiently small to be ignored, which has an impact on the toggle type clamping unit. Furthermore, compared to traditional methods, the optimal clamping force obtained using the method proposed in the present study results in a significant improvement in the yield rate. Overall, the results confirm that for low-viscosity polymer resins, the optimal clamping force determined using the proposed method results in a higher and more consistent quality of the molded parts than that achieved using the proper clamping force setting for ordinary-viscosity resins.

中文翻译：

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低粘度聚合物注射成型的锁模力优化

摘要 注射成型由于成本低、效率高，如今已被大量用于塑料制品的批量生产。但是，在加工低粘度塑料材料，即流动性好的材料时，如果夹紧力设置不当，往往会导致最终产品的外观和尺寸精度不佳。因此，操作者在设置机器时通常将锁模力的上限作为默认值，以试图提高模制件的质量。然而，这种方法会缩短机器和模具的寿命，增加能耗，并导致排气不良。因此，需要更科学的方法来确定锁模力设置。为了满足这个需求，本研究提出了一种合模力搜索方法，用于确定液压缸合模注塑机在加工热塑性聚氨酯 (TPU) 和聚丙烯 (PP) 等低粘度塑料时的最佳合模力设置。基于在不同夹紧力设置下从传感拉杆伸长率曲线中提取的特征，对这些数据点进行回归分析以寻求最佳夹紧力。实验结果表明，对于带有液压缸合模机构的注塑机，模具温度对合模力的影响小到可以忽略不计，对肘节式合模装置有影响。此外，与传统方法相比，使用本研究中提出的方法获得的最佳夹紧力可显着提高产量。总体而言，结果证实，对于低粘度聚合物树脂，使用所提出的方法确定的最佳锁模力比使用适当的普通粘度树脂设置的锁模力获得的模塑零件质量更高、更一致。