Plastic Shrinkage Analysis And Post-processing Shrinkage Prediction Based On Grey System Theory

Plastic industry is an essential part for our life in the modern society. The accuracy of plastic products are affected by shrinkage. Plastic parts shrinkage are affected by mold design, plastic parts structure, injection molding process and plastics post-processing. Parameters and post-processing are important for plastic shrinkage.The reason of shrinkage during the injection molding process is analyzed in this paper. A basic model which is named automotive active safety radar enclosure is built. This model is used to analysis products shrinkage rate with different parameters in MOLDFLOW software, such as injection temperature, mold temperature, injection time, holding time, cooling time, holding pressure, injection pressure and injection molding process parameters. The data which is obtained from simulation experiment and orthogonal experiment method are calculated by range analysis and variance analysis. Shrinkage reason is analyzed through range data analysis. Then the optimizing parameters for minimum plastic shrinkage rate are obtained. Three highest contribution rate of products parameters are analyzed through variance analysis. Three factors are injection temperature, mold temperature and cooling time.The basic grey theory system is combined with injection molding in this article. The article designs the molding grey theory system with injection temperature, mold temperature and cooling time. The result is that MOLDFLOW injection shrinkage value and the GM (1,1) grey prediction injection shrinkage value are consistent. The errors are within 2.2% and the change trend is same. It helps us to explore a new way to predict injection molding products shrinkage.Experiment is to analyze the post-processing shrinkage. It helps us to find the impact of annealing or wet for injection products shrinkage. Different temperature and humidity are set up to compare products post-processing shrinkage change. Then post-processing shrinkage effect on products can be judged through test. The result is that sealing performance is best at temperature at 25℃,45% humidity, the post-processing shrinkage change is minimum. The result shows that the part can comply with the requirement of industrial production.In this paper, it gives us a guidance to study molding shrinkage rate. It has a certain theoretical and practical significance.