Working principle of die-cutting machine

The working principle of injection molding machine is similar to that of injector. It is a process of injecting molten plasticized plastic (that is, viscous fluid state) into a closed mold cavity with the help of the thrust of a screw (or plunger), and curing to obtain a product.

Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding-melt plasticization-pressure injection molding-mold filling and cooling-mold opening and taking parts. Take out the plastic part, and then close the mold for the next cycle. Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding-melt plasticization-pressure injection molding-mold filling and cooling-mold opening and taking out, and then closing the mold for the next cycle.

Operation items of injection molding machine: Operation items of injection molding machine include control keyboard operation, electric control system operation and hydraulic system operation. Selection of injection process action, feeding action, injection pressure, injection speed and ejection type, monitoring of temperature in each section of the barrel, adjustment of injection pressure and back pressure, etc.

The molding process of screw injection molding machine is generally as follows: firstly, granular or powdery plastic is added into the barrel, and the plastic is in a molten state through the rotation of the screw and the heating of the outer wall of the barrel; Then, the machine closes the mold, and the injection seat moves forward to make the nozzle close to the gate of the mold; Then, pressurized oil is pumped into the injection cylinder to push the screw forward, so that the molten material is injected into the closed mold at low temperature at high pressure and high speed. After a certain period of time and pressure maintaining (also called pressure maintaining) cooling, the product can be taken out after opening the mold (the purpose of pressure maintaining is to prevent the molten material in the mold cavity from flowing back, replenish the material in the mold cavity, and ensure that the product has certain density and dimensional tolerance). 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 ensure sufficient pressure and speed. At the same time, due to the high injection pressure, a relatively 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 enough clamping force. It can be seen that injection device and clamping device are the key components of injection molding machine.

There are three main aspects in the evaluation of plastic products. The first is the appearance quality, including integrity and color. Second, the accuracy between size and relative position; The third is the physical properties, chemical properties and electrical properties corresponding to the use. These quality requirements have different scales according to the application of products. The defects of the product mainly lie in the design, manufacturing accuracy and wear degree of the mold. But in fact, technicians in plastic processing plants often encounter such a dilemma: using technical means to make up for the problems caused by mold defects has little effect.

Process adjustment in 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 mastered, waste products will emerge one after another. It is best to change only one condition at a time and observe it several times. If the pressure, temperature and time are all adjusted together, it is easy to cause confusion and misunderstanding, and I don't know why there is a problem. There are many measures and means to adjust the process. For example, there are more than a dozen possible solutions to the problem that the product label does not meet the requirements. Only by choosing one or two major solutions to solve the crux of the problem can we really solve the problem. In addition, we should pay attention to the dialectical relationship in solving problems. For example, if the product is sunken, sometimes the material temperature should be increased and sometimes the material temperature should be lowered; Sometimes it is necessary to increase the quantity of materials, and sometimes it is necessary to reduce the quantity of materials. It is necessary to realize the feasibility of using reverse measures to solve the problem.