The process of plastic injection molding is: the plastic particles are processed into a melt at high temperature, the melt is compressed into the cavity of the plastic mold by the screw of the molding machine, and a plastic part is formed after cold cutting. In this series of molding processes, there are orientation and crystallization effects, the cooling rate of each part of the melt is extremely difficult to achieve uniformity, the melt plasticization is not uniform, and the product is difficult to demould, etc., all of which will cause internal stress, which will lead to Plastic parts become brittle, deformed, and have poor appearance. The generation of internal stress is affected by many factors. The editor of Kehua is talking about the influence of injection molding conditions on the internal stress of plastic parts.

1. The influence of the barrel temperature of the molding machine on the internal stress: the temperature is high, the material is fully plasticized, the viscosity of the material is reduced, and the fluidity is relatively good, and the stress during the filling process in the cavity is naturally relatively low. Too high a temperature is not good either, because cold cutting is difficult and the cold shear stress increases.

2. The influence of mold temperature on internal stress: mold temperature has obvious effect on stress, low mold temperature, too fast cold cutting, uneven cold cutting, different cold cutting speed on the inner and outer surfaces of plastic parts, resulting in internal stress

3. The influence of molding injection pressure on internal stress: Generally speaking, the greater the injection pressure, the greater the possibility of causing stress

4. The influence of the pressure holding in the molding process on the internal stress: During the cold cutting process, the plastic parts are stabilized by holding the pressure. However, if the holding pressure is too large, it is easy to generate stress.

5. The influence of the holding time on the internal stress during the molding process: the longer the holding time, the greater the internal stress, so the appropriate holding time is part of scientific molding

6. The influence of injection speed on internal stress: The faster the injection speed, the greater the internal stress. Experienced machine adjustment masters will adopt segmented injection speed to achieve the balance between injection speed and stress.