What are the preparations for precision mold plastic injection molding

The plastic injection molding process of precision molds includes preparation before molding, injection process, and post-processing of products.　　Precision mold plastic injection molding preparation: 　　In order to make the injection molding process smoothly and ensure the quality of plastic parts, the factory preparation work should be carried out before injection molding: 　　(1) Raw material inspection and pretreatment. The raw materials should be inspected for appearance and process performance, dyed and dried before molding. The inspection of raw materials includes the determination of color, particle size and uniformity, fluidity, thermal stability, shrinkage, and moisture content. In order to make the molded plastic parts more beautiful, or to meet the requirements of use (the parts in the optical instrument need to be black to prevent light leakage), the plastic raw materials are usually dyed. Thermoplastics contain more or less moisture and volatiles, and an appropriate amount of moisture and volatiles can play a role in plasticizing. However, when the content of moisture and volatile matter exceeds a certain amount, it will cause defects in the plastic parts. In severe cases, bubbles will be generated, which will affect the quality and accuracy of the plastic parts. Therefore, it is necessary to dry it at this time. Drying is the use of high temperature to reduce the moisture content in the plastic. Methods include oven drying, infrared drying, hot plate drying, high-frequency drying, etc. The first two drying methods are usually used for thermoplastics.　　(2) Preheating of inserts. The difference between the shrinkage rate of metal inserts and plastics is large, so when the plastics cools, a large internal stress is generated around the inserts, which leads to a decrease in the strength of the plastic layer around the inserts and cracks. Therefore, the metal insert is preheated before molding to reduce the temperature difference between the insert and the plastic. For plastics that are not prone to stress cracking during molding, and the insert is small, preheating is not necessary. The preheating temperature is limited to not damaging the zinc layer or chromium layer plated on the surface of the metal insert, which is generally 110-130°C. For aluminum alloy or copper inserts with no coating on the surface, the preheating temperature can reach 150°C.　　(3) Cleaning of the barrel. Before injection molding, when the original residual plastic in the barrel of the injection machine is different from the plastic to be used or the color is the same, it must be cleaned.　　 (4) Selection of release agent. In injection molding, the demolding of plastic parts mainly depends on reasonable process conditions and correct mold design. However, due to the complexity of the plastic part itself or the stable control of process conditions, it may be difficult to demold, so it is often in actual production. Use a release agent. Due to the different types and shapes of injection materials, the structure of the plastic parts, the presence or absence of inserts, and the requirements for use, the preparation work before molding of various precision molds is not exactly the same.