The working principle of the injection molding machine is similar to that of the syringe for injection. It is to inject the plasticized molten state (ie, the viscous flow state) into the closed cavity by the thrust of the screw (or plunger). The process of obtaining the product after curing and setting.
Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding - melt plasticizing - pressure injection - filling mold cooling - mold extraction. After removing the plastic part, the mold is closed again for the next cycle.
Injection molding machine operation items: Injection molding machine operation items include three aspects: control keyboard operation, electrical control system operation and hydraulic system operation. The injection process action, the feeding action, the injection pressure, the injection speed, the selection of the ejection type, the monitoring of the temperature of each section of the barrel, the adjustment of the injection pressure and the back pressure are performed.
Generally, the molding process of the screw type injection molding machine is: firstly, the granular or powdered plastic is added into the barrel, and the plastic is melted by the rotation of the screw and the outer wall of the barrel, and then the machine performs the mold clamping and the injection seat forward. The nozzle is placed close to the gate of the mold, and then the pressure oil is introduced into the injection cylinder to advance the screw, thereby injecting the melt into the lower temperature closed mold at a high pressure and a relatively high speed. Time and pressure are maintained (also known as holding pressure), cooled, and solidified, and the product can be opened by mold opening (the purpose of holding pressure is to prevent backflow of molten material in the cavity, replenish material into the cavity, and ensure the product Has a certain density and dimensional tolerance). The basic requirements for injection molding are plasticization, injection and molding. Plasticization is the premise to achieve and guarantee the quality of molded products, and in order to meet the molding requirements, the 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 cavity (the average pressure in the cavity is generally between 20 and 45 MPa), so a sufficient clamping force must be obtained. It can be seen that the injection device and the clamping device are key components of the injection molding machine.
There are three main aspects for the evaluation of plastic products. The first is the appearance quality, including integrity, color, gloss, etc.; the second is the accuracy between size and relative position; the third is the physical properties and chemical properties corresponding to the application. Electrical properties, etc. These quality requirements are different depending on the use of the product. The defects of the product mainly lie in the design, manufacturing precision and wear degree of the mold. But in fact, technicians in plastic processing plants often suffer from the difficult situation of using technology to compensate for the problems caused by mold defects.
Process adjustment during production is a necessary way to improve product quality and yield. Since the injection cycle itself is very short, if the process conditions are not well mastered, the waste will continue to flow. When adjusting the process, it is best to change only one condition at a time, and observe a few more times. If the pressure, temperature, and time are unified and uplifted, it is easy to cause confusion and misunderstanding. If there is a problem, it does not know what it is. The measures and means to adjust the process are various. For example, there are more than a dozen possible solutions to solve the problem of product dissatisfaction. It is necessary to choose one or two major solutions to solve the problem and solve the problem. In addition, attention should be paid to the dialectical relationship in the solution. For example, the product has a depression, sometimes it is necessary to increase the temperature of the material, sometimes to reduce the temperature of the material; sometimes to increase the amount of material, and sometimes to reduce the amount of material. It is necessary to recognize the feasibility of solving the problem of reverse measures.
