Injection molding machine is also known as injection molding machine or injection molding machine. It is the main molding equipment for making thermoplastic or thermosetting plastics into plastic products of various shapes using plastic molding molds. It is divided into vertical type, horizontal type and all electric type. The injection molding machine heats the plastic and applies high pressure to the molten plastic to make it eject and fill the mold cavity.
The working principle of the injection molding machine is similar to that of the syringe for injection. It is a technological process that uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (i.e. viscous flow state) into the closed mold cavity, and obtain products after curing and shaping.
Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding - melt plasticization - pressure injection - mold filling and cooling - mold opening and part taking. Take out the plastic parts and then close the mold for the next cycle.
Injection molding machine operation items: injection molding machine operation items include control keyboard operation, electrical control system operation and hydraulic system operation. Select the injection process action, feeding action, injection pressure, injection speed, ejection type, monitor the temperature of each section of the barrel, and adjust the injection pressure and back pressure.
Generally, the molding process of screw injection molding machine is as follows: first, granular or powdered plastic is added into the barrel, and the plastic is melted through the rotation of the screw and the heating of the outer wall of the barrel. Then, the machine carries out mold closing and moves the injection seat forward, so that the nozzle is close to the gate of the mold. Then, pressure oil is injected into the injection cylinder to push the screw forward, Thus, molten materials are injected into a closed mold with low temperature at a very high pressure and fast speed. After a certain period of time and pressure (also known as pressure holding) and cooling, the mold can be solidified and shaped, and then the products can be taken out of the mold (the purpose of pressure holding is to prevent reverse flow of molten materials in the mold cavity, supplement materials to the mold cavity, and ensure that the products have a certain density and dimensional tolerance). The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the premise to achieve and ensure the quality of molded products. In order to meet the requirements of molding, injection must have sufficient pressure and speed. At the same time, due to the high injection pressure, a high pressure will be generated in the mold cavity (the average pressure in the mold cavity is generally between 20 and 45 MPa), so there must be enough mold closing force. It can be seen that the injection device and the clamping device are the key components of the injection molding machine.
The evaluation of plastic products mainly includes three aspects: the first is the appearance quality, including integrity, color, luster, etc; The second is the accuracy between size and relative position; The third is the physical, chemical and electrical properties corresponding to the purpose. These quality requirements are also different according to the different application occasions of the products. The defects of products mainly lie in mold design, manufacturing accuracy and wear degree. However, in fact, the technicians of plastic processing plants are often suffering from the difficult situation of making up for the problems caused by mold defects by technological means with little effect.
The adjustment of technology in the production process is a necessary way to improve the quality and output of products. Because the injection molding cycle itself is very short, if the process conditions are not well mastered, there will be an endless stream of waste products. It is better to change only one condition at a time when adjusting the process, and observe several times. If the pressure, temperature and time are adjusted together, it is easy to cause confusion and misunderstanding, and we don't know what the reason is when there is a problem. There are many measures and means to adjust the process. For example, there are more than ten possible solutions to solve the problem of insufficient product injection. Only by choosing one or two major solutions to solve the problem, can we truly solve the problem. In addition, we should also pay attention to the dialectical relationship in the solution. For example, if the product has dents, sometimes the material temperature needs to be raised, sometimes the material temperature needs to be lowered; Sometimes it is necessary to increase the material quantity, sometimes it is necessary to reduce the material quantity. It is necessary to acknowledge the feasibility of solving the problem by means of reverse measures.