Cooling System Of Injection Mold Injection Molding Performance

The effect of molding cooling temperature on the microstructure and mechanical properties of the PP injection product was deeply studied. The results showed that cooling temperature affected the mechanical properties of PP products by means of affecting its microstructure, especially crystallographic structure and the thickness of orientation skin. With the cooling temperature being increased, the crystalline size, crystallinity, tensile strength and surface hardness of propylene increased correspondingly. Meanwhile, the thickness of orientation skin, impact strength and volume shrinkage decreased. In addition, the influence of molding temperature and injection pressure on PS product was discussed, too. All these became the foundation of searching for the optimum cooling temperature. Synthetically considered the mechanical properties of injection slab, 55～65℃ was recommended as the optimum average surface temperature of mould profile, PS was 45～55℃. In order to control the optimum surface cooling temperature uniformly and accurately, it was necessary to study the design of mould cooling system deeply. In the beginning, practical cooling system design theory was provided. Then more precise design method was lucubrated. Based on one dimensional transient heat transfer theory, the transient temperature of polymer melt and flux between mold and polymer melt are analyzed. Meanwhile, the two dimensional cycle average temperature field of mold was studied deeply, the modified boundary element methods for two dimensions has been used to formulate the linear boundary integral equations which provided convenience for solving temperature field by using of iterative algorithm. In the end, according to the mathematic optimization method, an object function, the average squared difference of cavity temperature from the object temperature, was formed. By taking the first-order Taylor expansion of the object function, an iterative method was used to search for the minimum value of the object function. Furthermore, choosing the cooling line radius and positions as design variables, the boundary integral design sensitivity formulations were given. As a result we got the optimal design method that could satisfy the requirement of uniform and accurate cooling temperature.