What is the working principle of injection molding machine?

Update:30-04-2020
Summary:

The working principle of the injection molding machine […]

The working principle of the injection molding machine is similar to the syringe used for injection. It uses the thrust of the screw (or plunger) to inject the plasticized molten state (that is, viscous flow) into the closed mold cavity. The process of obtaining products after curing and shaping.
Injection molding is a cyclic process, each cycle mainly includes: quantitative feeding-melt plasticization-pressure injection-mold filling cooling-mold take-out. After removing the plastic parts, the mold is closed again for the next cycle.
Injection molding machine operation project: The injection molding machine operation project includes three aspects: control keyboard operation, electrical control system operation and hydraulic system operation. Select the injection process action, feeding action, injection pressure, injection speed, ejection type selection, temperature monitoring of each section of the barrel, adjustment of injection pressure and back pressure, etc.


The molding process of a general screw injection molding machine is: first, granular or powder plastic is added to the barrel, and the plastic is melted by the rotation of the screw and the outer wall of the barrel, and then the machine closes the mold and the injection seat moves forward. Keep the nozzle close to the gate of the mold, and then feed the injection cylinder with pressure oil to advance the screw, so that the molten material is injected into the closed mold with a lower temperature at a high pressure and a faster speed. Time and pressure are maintained (also known as holding pressure), cooling, and solidification, and the product can be opened to remove the product (the purpose of holding pressure is to prevent the backflow of the melt in the mold cavity, supplement the material into the mold cavity, and ensure the product Have a certain density and dimensional tolerance). The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the prerequisite for achieving and ensuring the quality of molded products, and in order to meet the requirements of molding, injection must ensure that there is sufficient pressure and speed. At the same time, due to the high injection pressure, a correspondingly high pressure is generated in the mold cavity (the average pressure in the mold cavity is generally between 20 and 45 MPa), so there must be a sufficiently large mold clamping force. It can be seen that the injection device and the mold clamping device are the key components of the injection molding machine.
There are three main aspects to the evaluation of plastic products. The first is the appearance quality, including completeness, color, gloss, etc .; the second is the accuracy between the size and relative position; the third is the physical properties, chemical properties, and Electrical performance, etc. These quality requirements are different according to the use occasions of the products, and the required standards are also different.
The defects of the products are mainly in the aspects of mold design, manufacturing accuracy and wear level. But in fact, the technical personnel of plastic processing plants often suffer from the difficult situation of using technology to make up for the problems caused by the defects of the mold and having little effect.
The adjustment of technology in the production process is a necessary way to improve product quality and output. Because the injection cycle itself is very short, if the process conditions are not well grasped, there will be an endless stream of waste products. When adjusting the process, it is best to change only one condition at a time, and observe a few times. If the pressure, temperature, and time are all adjusted up, it is easy to cause confusion and misunderstanding. If there is a problem, I do n’t know why. The measures and means to adjust the process are various. For example, there are more than ten possible solutions to solve the problem of product dissatisfaction. Only one or two main solutions to solve the crux of the problem can be selected to solve the problem. In addition, we should pay attention to the dialectical relationship in the solution. For example: the product has a depression, sometimes it is necessary to increase the material temperature, sometimes it is necessary to reduce the material temperature; sometimes it is necessary to increase the amount of material, sometimes it is necessary to reduce the amount of material. Recognize the feasibility of reverse measures to solve problems

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