Working Principle Of 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 plastic that has been plasticized into the molten state (that is, the viscous flow state) into the closed cavity. The process of obtaining products after curing and setting.

Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding—melt plasticization—pressure injection—mold filling and cooling—mold opening and pick-up. After taking out the plastic parts, the mold is closed again, and the next cycle is carried out.

Injection molding machine operation items: Injection molding machine operation items include three aspects: control keyboard operation, electrical control system operation and hydraulic system operation. Carry out the injection process action, feeding action, injection pressure, injection speed, selection of ejection type, temperature monitoring of each section of the barrel, adjustment of injection pressure and back pressure, etc.

The molding process of the general screw injection molding machine is: firstly, the granular or powdery plastic is added into the barrel, and the plastic is melted through the rotation of the screw and the outer wall of the barrel is heated, and then the machine is closed and the injection seat is moved forward. Make the nozzle close to the sprue of the mold, and then feed the pressure oil into the injection cylinder to push the screw forward, so that the molten material is injected into the closed mold at a high pressure and at a faster speed. Keep time and pressure (also known as holding pressure), cool it, make it solidify and form, and then open the mold and take out the product (the purpose of holding pressure is to prevent the backflow of the molten material in the mold cavity, replenish materials into the mold cavity, and ensure that the product with certain density and dimensional tolerances). The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the prerequisite to realize and guarantee the quality of molded products, and in order to meet the requirements of molding, injection must ensure 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 20~45MPa), so there must be a large enough clamping force. It can be seen that the injection device and the 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 integrity, color, gloss, etc.; the second is the accuracy of size and relative position; the third is the physical properties, chemical properties, electrical properties etc. These quality requirements are different according to the use occasions of the products, and the required scales are also different. The defect of the product mainly lies in the design of the mold, the manufacturing accuracy and the degree of wear and so on. But in fact, technicians in plastic processing plants often face the difficult situation of using technological means to make up for the problems caused by mold defects with little success.

The adjustment of the process in the production process is a necessary way to improve the quality and output of products. Since the injection molding 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 several times. If the pressure, temperature, and time are all adjusted together, it will easily cause confusion and misunderstanding. If something goes wrong, you don’t know the reason. There are many measures and means to adjust the process. For example: there are more than ten possible solutions to solve the problem of product dissatisfaction. Only by choosing one or two main solutions to solve the crux of the problem can the problem be truly solved. In addition, attention should be paid to the dialectical relationship in the solution. For example, if the product has a dent, sometimes it is necessary to increase the temperature of the material, and sometimes it is necessary to reduce the temperature of the material; sometimes it is necessary to increase the amount of material, and sometimes it is necessary to reduce the amount of material. Recognize the feasibility of countermeasures to solve the problem.