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What is an injection mold? Today I will tell you thoroughly that thousands of products are produced by him (Part 4)

Although the structure of plastic molds may vary due to different types and properties of plastics, shapes and structures of plastic products, and types of injection machines, the basic structure is the same.

1. Plastic mold structure is divided according to function
It is mainly composed of: pouring system, temperature adjustment system, molded parts system, exhaust system, guide system, ejection system, etc. Among them, the pouring system and molded parts are the parts that are in direct contact with plastics and change with the plastics and products. They are the most complex and changing parts of the mold and require the highest processing smoothness and precision.

1.Gouring system:
It refers to the runner part before the plastic enters the cavity from the nozzle, including the main channel, cold material cavity, runner and gate, etc.

2. Molded parts system:
It refers to the combination of various parts that constitute the shape of the product, including the movable mold, the fixed mold and the cavity (concave mold), core (convex mold), forming rod, etc. The core forms the inner surface of the product, and the cavity (die) forms the outer surface shape of the product. After the mold is closed, the core and cavity form the cavity of the mold. According to the process and manufacturing requirements, sometimes the core and the die are composed of several pieces, sometimes they are made as a whole, and inserts are only used in parts that are easily damaged and difficult to process.

3. Temperature adjustment system:
In order to meet the mold temperature requirements of the injection process, a temperature adjustment system is required to adjust the temperature of the mold. For injection molds for thermoplastic plastics, the cooling system is mainly designed to cool the mold (the mold can also be heated). The common way to cool the mold is to open a cooling water channel in the mold, and use the circulating cooling water to take away the heat of the mold. In addition to using the cooling water to pass hot water or hot oil, the heating of the mold can also be installed inside and around the mold. Electric heating element.
4. Exhaust system:
It is set up to discharge the air in the cavity and the gas generated by the melted plastic out of the mold during the injection molding process. When the exhaust is not smooth, air marks (air marks), scorching and other defects will be formed on the surface of the product; the exhaust of the plastic mold The air system is usually a groove-shaped air outlet opened in the mold to discharge the air in the original cavity and the gas brought in by the melt.

When the molten material is injected into the mold cavity, the air originally existing in the mold cavity and the gas brought in by the melt must be discharged out of the mold through the exhaust port at the end of the material flow. Otherwise, the product will have pores, poor connections, and The mold filling is not satisfactory, and the accumulated air may even burn the product due to high temperature caused by compression. Under normal circumstances, the exhaust hole can be located either at the end of the melt flow in the cavity or on the parting surface of the mold.

The latter is to open a shallow groove with a depth of 0.03-0.2mm and a width of 1.5-6mm on one side of the die. During injection, a lot of molten material will not seep out of the vent hole, because the molten material will cool and solidify there and block the channel. The exhaust port must not be opened facing the operator to prevent the molten material from accidentally spraying out and injuring people. In addition, the matching gap between the ejector rod and the ejector hole, the matching gap between the ejector block and the stripping plate and the core can also be used to exhaust air.

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