The problem of shrinkage of plastic parts (surface shrinkage and internal shrinkage) is due to defects caused by insufficient filling of the melt when the thicker part is cooled. We often encounter situations where the pressure is increased, the water inlet is increased, the injection time is prolonged, and the shrinkage problem cannot be solved.
Among the commonly used raw materials, due to the fast cooling rate, the shrinkage of the PC material is the most difficult to solve, and the shrinkage and shrinkage of the PP material is also difficult to handle. Therefore, when encountering a serious shrinkage problem with thick parts, it is necessary to take some unconventional injection molding techniques, otherwise it will be difficult to solve the problem.
Under the premise of ensuring that the injection molded parts are not deformed, the method of minimizing the cooling time is adopted to allow the injection molded parts to be prematurely released at a high temperature. At this time, the temperature of the outer layer of the injection molded part is still high, and the skin is not too hardened, so the temperature difference between the inside and the outside is relatively small, which is advantageous for the overall shrinkage, thereby reducing the concentrated shrinkage inside the injection molded part.
Since the overall shrinkage of the injection molded part is constant, the more the overall shrinkage is, the smaller the concentrated shrinkage is, and the degree of internal shrinkage and surface shrinkage is thus reduced.