1.1 working principle of injection molding machine

　　The working principle of the injection molding machine is similar to that of the syringe for injection. It is a technological process in which the plasticized plastic in the molten state (i.e. viscous flow state) is injected into the closed mold cavity with the help of the thrust of the screw (or plunger), and the product is obtained after solidification and finalization.

　　Injection molding is a cycle process, each cycle mainly includes: quantitative feeding, melting and plasticizing, pressure injection, mold filling and cooling, mold opening and taking. Take out the plastic part and then close the mold for the next cycle.

　　1.2 structure of injection molding machine

　　The injection molding machine can be divided into plunger type injection molding machine and screw type injection molding machine according to the plasticizing mode; it can be divided into hydraulic type, mechanical type and hydraulic mechanical (connecting rod) type according to the transmission mode of the machine; it can be divided into automatic, semi-automatic and manual injection molding machines according to the operation mode.

　　(1) Horizontal injection molding machine: This is the most common type. The mold closing part and the injection part are on the same horizontal center line, and the mold is opened in the horizontal direction. Its features are: short fuselage, easy to operate and maintain; low center of gravity of the machine, relatively stable installation; after the product is ejected, it can automatically fall down by gravity, easy to realize full-automatic operation. At present, this type of injection molding machine is widely used in the market.

　　(2) Vertical injection molding machine: the mold closing part and the injection part are on the same vertical center line, and the mold is opened in the vertical direction. Therefore, the utility model has the advantages of small floor area, easy placement of inserts, convenient loading and unloading of molds, and even plasticization of materials falling into the hopper. However, it is not easy for the product to fall down automatically after ejection, so it must be taken down by hand, and it is not easy to realize automatic operation. Vertical injection molding machine is suitable for small-scale injection molding machine, generally less than 60g injection molding machine is used more, large and medium-sized machines are not suitable.

　　(3) Angle type injection molding machine: its injection direction is on the same surface as the mold interface, which is especially suitable for plane products with no gate trace in the machining center. It covers a smaller area than horizontal injection molding machine, but the inserts put into the mold are easy to fall obliquely. This type of injection molding machine is suitable for small machines.

　　(4) Multi mode rotary injection molding machine: it is a special injection molding machine with multi position operation. Its feature is that the mold closing device adopts the rotary structure, and the mold rotates around the rotating shaft. This type of injection molding machine can give full play to the plasticizing ability of the injection device, shorten the production cycle, and improve the production capacity of the machine. Therefore, it is especially suitable for the production of large batch of plastic products with long cooling time or more auxiliary time due to the placement of inserts. However, due to the large and complex mold closing system, the mold closing force of the mold closing device is often small, so this injection molding machine is used in plastic Sole and other products are widely used in production.

　　General injection molding machine includes injection device, mold closing device, hydraulic system and electrical control system.

　　The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the premise of realizing and ensuring the quality of molded products, and in order to meet the requirements of molding, injection must be guaranteed to have enough pressure and speed. At the same time, due to the high injection pressure, the corresponding high pressure is generated in the mold cavity (the average pressure in the mold cavity is generally between 20-45mpa, see Table 1), so there must be enough mold closing force. It can be seen that the injection device and the mold closing device are the key parts of the injection molding machine