On the most popular injection molding technology 1

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Plastic is a new type of material synthesized artificially by people with chemical methods. The products processed from various plastics have become an indispensable means of production and living in all sectors of China's national economy and people's lives. Injection molding is the most commonly used method in plastic molding processing. Injection molding can realize production automation, high-speed, and high economic benefits

in the face of huge market demand, businesses have invested a lot of money in the injection molding industry and purchased injection molding machines and raw materials. Then, how can we turn raw materials into converging products of Jinan experimental machine industry? This involves injection molding processing technology. Only by mastering this technology can we process high-quality products and create higher production benefits

injection molding is a cycle process, and each cycle includes: raw material pretreatment, quantitative feeding, melting and plasticizing, pressure injection, mold filling, cooling, mold opening, parts taking and product processing. Injection molding processing technology is the parameters to be controlled and the problems to be paid attention to in each process of the whole cycle. The following is a brief description of the process technology in each process

the first is the pretreatment of raw materials, including drying and color mixing of raw materials. Some plastics, such as polycarbonate (PC), polyamide (PA) and polyethylene terephthalate (PET), because their macromolecules contain hydrophilic substances, which are easy to absorb moisture, so they contain varying degrees of moisture. A batch of key new material standards have been completed in a complete set and system. When the water content is higher than the regulations, the product surface may have defects such as silver wire, stripes and bubbles; The most serious problem is that the polymer material in the material is degraded during injection. Generally, the plastics for mass production should be dried by boiling or air flow. Each kind of plastics has the best drying temperature and time. If the time is too long, the effect is not good. See Table 1 for the drying temperature and time of some plastics (taking Xinyi SDL direct link hopper as an example):

Table 1

1 PE, PS, PP 80

2 nylon seriv 75

3 ABS As

4 PC 120

5 PVC 70

however, if the hydrophilic plastics such as pet are dried, it is powerless to use only ordinary drying hoppers. In addition, vacuum ovens or dehumidifiers are required, in which the dehumidifier can realize continuous production. When processing pet bottle embryo, the company used a SD-90 dehumidifier of Xinyi to dry continuously for 5 hours at 140 ℃, which can remove 98% of the water contained, and the effect is very remarkable. As for mixing, it is mainly used in some manufacturing, metallurgy and building materials industries. Generally, the mixer is used. If the content of masterbatch needs to be accurately controlled, the masterbatch metering mixer can be used. For example, CF series produced in Sweden can control the metering of masterbatch according to the operation of the machine

the second is quantitative feeding, which is related to the accuracy of the machine

the third is melt plasticization. The following three aspects should be mentioned in this process:

1. Correct selection of barrel and screw; Select the correct barrel and screw according to the processing performance of the plastic. According to the characteristics of some plastics, our company has developed many special screws and barrels for customers to choose, such as exhaust screws, separation screws, special screws and barrels for thermosetting plastics, PVC screws, PC screws and bimetal barrels, screws, etc

2. Setting of heating temperature; The selection of barrel temperature is related to the characteristics of various plastics. Each kind of plastics has its own viscous flow temperature (T1) and melting point (T2), and there is also a decomposition temperature (T3). Be familiar with the working principle, operating procedures and normal maintenance of equipment

the most appropriate temperature of the barrel should be between T1-T3 or T2-T3. If this range is small, the barrel temperature should be low, otherwise it can be appropriately increased. See Table 2 for the temperature of several commonly used plastics. (to be continued)

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