Abstract
Injection molding is a popular process for the mass production of polymer products, but due to the characteristics of the injection process, there are many factors that will affect the product quality during the long fabrication processes. In this study, an adaptive adjustment system was developed by C++ programming to adjust the V/P switchover point and injection speed during the injection molding process in order to minimize the variation of the product weight. Based on a series of preliminary experiments, it was found that the viscosity index and peak pressure had a strong correlation with the weight of the injection-molded parts. Therefore, the viscosity index and peak pressure are used to guide the adjustment in the presented control system, and only one nozzle pressure sensor is used in the system. The results of the preliminary experiments indicate that the reduction of the packing time and setting enough clamping force can decrease the variation of the injected weight without turning on the adaptive control system; meanwhile, the master pressure curve obtained from the preliminary experiment was used as the control target of the system. With this system, the variation of the product weight and coefficient of variation (CV) of the product weight can be decreased to 0.21 and 0.05%, respectively.
Highlights
Malinowski [1] mentioned that, during processing, decreasing uncertainty related to product quality was a very important issue for injection molding processing, with environmental factors, plastic flow resistance, material changes, and human factors being considered to be causes of such an uncertainty.The injection molding process can be divided into seven stages: plasticization, clamping, injection, packing, cooling, demolding and ejecting
The results showed that the peak pressure, viscosity index, and product weight had the same trend and that the variations of the product weight clearly decreased
The relationships among the peak pressure, viscosity index, and product weight can be clearly seen in Figure 8a–c, which verifies that the product weight has a very weight can be clearly seen in Figure 8a–c, which verifies that the product weight has a strong proportional relationship with the viscosity index and peak pressure
Summary
The injection molding process can be divided into seven stages: plasticization, clamping, injection, packing, cooling, demolding and ejecting. Injection and packing are the stages that have been suggested to have the greatest effects on product quality. Kazmer et al [2] mentioned that changes in the screw position and injection pressure were conditions that could decrease product quality uncertainty. In the case of polymer materials, the P–V–T (Pressure-Specific Volume–Temperature) relationship is very important because there is a strong relationship between pressure, volume, and temperature, and the specific volume affects the product weight significantly. Using the relationship between pressure and temperature to maintain a specific volume can lead to a constant product weight
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