1. Shrinkage in injection molding isInjection moldingIt is a very common problem, especially for plastic products with high surface quality requirements. Therefore, with the continuous improvement of injection molding technology, it is imperative to minimize the shrinkage of injection molding and improve product quality.

2. The shrinkage formed in the thicker part of plastic parts (such as ribs or protrusions) is more serious than that of adjacent parts. This is because the thicker part cools much slower than the surrounding area. Different cooling rates will lead to the formation of dents on the joint surface, which is called shrinkage marks. This defect seriously limits the design and molding of plastic products, especially large thick wall products such as TV inclined boxes, display boxes and so on. In fact, products with strict requirements such as household appliances need to remove shrinkage holes, while toys and other products with low surface quality requirements are allowed to have shrinkage marks during injection molding.

3. There may be one or more reasons for forming shrinkage marks in injection molding, including processing method, part geometry, material selection, mold design, etc. Geometry and material selection are usually decided by the raw material supplier and cannot be easily changed. However, in mold manufacturers, there are many factors related to mold design that may affect the shrinkage of injection molding. The design of cooling channel, gate type and gate size may have different effects. For example, a small gate, such as a tubular gate, cools much faster than a conical gate. Premature cooling of the gate will reduce the filling time of the cavity, thereby increasing the possibility of shrinkage marks. For molding workers, adjusting processing conditions is a way to solve the shrinkage problem in injection molding. Filling pressure and time significantly affect the shrinkage. After the part is filled, the excess material continues to fill the cavity to compensate for the shrinkage of the material. If the filling stage is too short, the shrinkage will intensify and eventually produce more or larger shrinkage marks. This method to solve the shrinkage of injection molding itself may not be able to reduce the shrinkage mark to a satisfactory degree, but the molding workers can adjust the filling conditions to improve the shrinkage mark.