Structural analysis of injection molding machine and its working principle

- Jul 13, 2019-

First, the working principle of the injection molding machine

The injection molding machine is referred to as an injection molding machine.

Injection molding uses the thermophysical properties of plastics to feed materials from the hopper into the barrel. The outside of the barrel is heated by the heating coil to melt the material. The barrel is equipped with a screw driven by an external power motor to drive the rotation. The material acts as a screw. Next, along the screw groove forward conveying and compaction, the material is gradually plasticized, melted and homogenized under the double action of external heating and screw shearing. When the screw rotates, the material is in the screw groove friction and shear force. Under the action, the molten material is pushed to the head of the screw, at the same time, the screw retreats under the reaction of the material, so that the screw head forms a storage space, the plasticizing process is completed, and then the piston thrust of the screw in the injection cylinder Under the action of high speed and high pressure, the molten material in the storage chamber is injected into the cavity of the mold through the nozzle. After the molten material in the cavity is pressed, cooled, solidified and shaped, the mold is under the action of the clamping mechanism. , the mold is opened, and the shaped product is ejected from the mold by the ejector device.

Second, the classification of injection molding machines

There are three types of horizontal, vertical and angle type according to the configuration of the mold clamping part and the injection part.

 (1) Horizontal injection molding machine: Horizontal injection molding machine is a very common type. It is characterized in that the center line of the injection assembly is concentric or coincident with the center line of the clamping assembly and parallel to the installation ground. Its advantages are low center of gravity, stable operation, convenient installation, operation and maintenance of the mold, large opening of the mold and small space occupation; but large area, large, medium and small machines are widely used.

(2) Vertical injection molding machine: it is characterized in that the axis of the clamping device and the injection device are arranged in a line and perpendicular to the ground. The utility model has the advantages of small occupied area, convenient assembly and disassembly of the mold, easy installation of the insert, plasticization of the material from the hopper falling into the material, and easy realization of automation and automatic line management of multiple machines. The disadvantage is that the ejector product is not easy to fall off automatically, and often needs to be taken out by manual or other methods, and it is difficult to realize full automatic operation and injection of large products; the body is high, feeding and maintenance are inconvenient.

(3) Angle injection molding machine: the axes of the injection device and the clamping device are vertically aligned with each other. According to the relative position of the center line of the injection assembly and the mounting base, there are horizontal, vertical and horizontal types: 1 horizontal, the injection assembly line is parallel to the base surface, and the center line of the clamping assembly is The base surface is vertical; 2 vertical, the center line of the injection assembly is perpendicular to the base surface, and the center line of the clamping assembly is parallel to the base surface. The advantage of the angle injection machine is that it has the advantages of both horizontal and vertical injection machines, and is particularly suitable for molds in which a side gate asymmetric geometric product is opened.

Third, the composition of the injection molding machine analysis

According to the injection molding process requirements, the injection molding machine is a highly mechatronic machine. It is mainly composed of injection parts, mold clamping parts, airframe, hydraulic system, heating system, control system and feeding device. as shown in picture 2.

(1) Typical structure of injection molded parts

1. The composition of the injection parts At present, the common injection molding equipment has a single cylinder form and a double cylinder form. The injection molding machines of our factory are all in the form of double cylinders, and all of them are directly driven by a hydraulic motor. Because the composition of different manufacturers and different types of machines is not exactly the same, the following is a detailed analysis of the machines used in our factory.

The composition diagrams of the vertical and horizontal injection molding units are shown in Figures 3 and 4, respectively.

The working principle is: when pre-plasticizing, the screw in the plasticizing part drives the main shaft to rotate by the hydraulic motor, one end of the main shaft is connected with the screw key, and the other end is connected with the hydraulic motor key. When the screw rotates, the material is plasticized and plasticized. The melt is pushed into the storage chamber at the front end of the barrel, at the same time, the screw retreats under the reaction of the material, and the thrust seat is retracted by the thrust bearing, and the piston rod is linearly retracted by the nut to complete the metering, injection, injection cylinder The rod cavity oil feeds through the bearing to push the piston rod to complete the action, and the piston rod cavity oil feeds the piston rod and the screw to complete the injection action.


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