Visualization Experiment Study For Rule Of Shrinkage Of Polyurethane Elastomer Moulding

Casting polyurethane elastomer(CPUE) is commonly called as liquid rubber. It has been widely used in many fields of the national economy for its excellent comprehensive performance. In recent years, because of increasing demand of the precision molding products, the research on molding shrinkage of high polymer material becomes a hotspot. Currently, the research on molding shrinkage of CPUE is relatively few. In this paper, the molding shrinkage of CPUE was studied. The research on impact of process conditions, structure and size factors on the molding shrinkage was conducted by visualization technology. Rule and mechanism of molding shrinkage were also exeplored and analyzed.A set of casting molding visualization experimental system was developed. It consis of and sensor measuring system, and has strong commonality. Using visual observing system, dynamic filling process of the melt and characteristic changes before and after shrinkage of products can be recorded to explore and analyze the rule and mechanism of the molding shrinkage. With sensor measuring system, the temperature change of the melt during the filling process could be observed, to provide the basis for the further analysis of mechanism of the molding shrinkage.A set of visual processing method was developed to analyze molding shrinkage of products. Dynamic visual processing method of molding process was further improved, basing on the experience of our group. And with this method, filling process could be researched from three parts, the overlay of flow front, filling rate and filling path of the melt. The evidence would be provided for explorer of mechanism of the molding shrinkage. A set of static visual processing method of inner shrinkage was developed, and the rule of inner shrinkage was systematically showed by this way through2D curve, contour map and Vector diagram.The results of macro shrinkage show that, in the experiment of process conditions, reasonable choice of material temperature can help to control difference of shrinkage rates in two directions. And in the wide range, the shrinkage rates in both two directions increase with the rise of mould temperature. In the experiment of structure factors, the effect of square blocks on the width shrinkage is more, and to circular blocks, that on the length shrinkage is greater. Meanwhile, in the experiment of size factors, shrinkage rate on the direction of length increases with the decrease of cavity thickness.The visualization results show that, orientation distribution of inner shrinkage is decided by the structure of products through filling path of the melt. And the length of flow path also have greater influence on the shrinkage.