Injection Molding Technology of Precision Mold in Shandong Province
Plastic injection moulding process includes preparation before moulding, injection process and product post-treatment.
1. Preparing for Plastic Injection Molding
In order to ensure the smooth progress of injection moulding and the quality of plastic parts, the factory should prepare for the following injection moulding:
(1) Inspection and pretreatment of raw materials. The appearance and technological properties of the material should be checked and dyed and dried before forming. The testing of raw materials includes the determination of color, particle size and uniformity, fluidity, thermal stability, shrinkage and moisture content. In order to make the processing of injection parts more beautiful, or to meet the requirements of use (optical equipment parts need black to prevent light leakage), plastic raw materials are usually dyed. Thermoplastics contain more or less water and volatile substances, and a proper amount of water and volatile substances can play a plasticizing role. But when the content of moisture and volatile matter exceeds a certain amount, it will cause defects on plastic parts, produce serious bubbles, affect the quality and accuracy of plastic parts, so drying treatment will be carried out at this time. The drying process is to use high temperature to reduce the moisture content of plastics. This method includes oven drying, infrared drying, hot plate drying, high frequency drying and the first two drying methods commonly used in thermoplastics.
(2) Gasket preheating. The shrinkage ratio of metal inserts is quite different from that of plastics, so when the plastic parts are cooled, there will be greater internal stress around the inserts, which will lead to the decrease of the strength of the plastic layer around the inserts and cracks. Therefore, the metal nesting is preheated before forming to reduce the temperature difference between the nesting and the plastic.
成型時不易產生應力開裂塑料，且嵌套小，不能預熱。預熱溫度限制在金屬鑲件表面的鋅或鉻鍍層，通常為110 ~ 130℃。對于表面無涂層的鋁合金或銅鑲件，預熱溫度可達150℃。
It is not easy to produce stress cracking plastics when forming, and the nesting is small, so it can not be preheated. The preheating temperature is limited to zinc or chromium plating on the surface of metal inserts, usually 110 - 130 C. For aluminium alloy or copper inserts without coating, the preheating temperature can reach 150 C.
(3) Cylinder cleaning. Before injection moulding, when the remaining plastic in the injection tube is different or the same color as the plastic used, it will be cleaned.
(4) Selection of release agent. In the process of injection moulding, the part of plastic demoulding mainly depends on reasonable process conditions and correct die design. However, due to the complexity of plastic parts or the control of stable process conditions, it may lead to demoulding difficulties, so demoulding agents are often used in actual production. Due to the different types of injection materials, the shape, structure, mosaic and usage requirements of the plastic parts, the preparation work before the forming of various plastic parts is also different.
The injection moulding process of Shandong Precision Mould is described above. For more information about Shandong Mould, please pay attention to the update of our website.