The working principle of the injection molding machine is similar to that of the syringe used for injection. It is a technological process in which plasticized and fused plastic (i.e., viscous flow) is injected into the closed mold cavity with the help of the thrust of the screw (or plunger), and the products are obtained after curing and shaping.Injection molding is a cyclical process, each cycle mainly includes: quantitative feeding - melt plasticizing - pressure injection - mold filling cooling - opening mold take.After take out the plastic mold closing again, for the next cycle.

Operation items of injection molding machine: operation items of injection molding machine include control keyboard operation, electrical control system operation and hydraulic system operation.The selection of injection process action, feeding action, injection pressure, injection speed, ejector type, temperature monitoring of each section of the cartridge, injection pressure and back pressure adjustment, etc.

General screw injection molding machine molding process is:First adding granular or powdered plastic barrel, and with the rotation of the screw and barrel outer wall heating make plastic molten state, then the machine forward, clamping and injection nozzle with mold gate way, then access to the injection cylinder pressure oil, make the screw to move forward, thus at high pressure and fast speed will be within the closed mold injection melting temperature is low, after a certain time and pressure maintenance (also known as the holding), cooling, make its curing, can open mold to take out the products (the holding of the purpose is to prevent cavity in the reverse flow of the molten material, supplementary material within the cavity,And to ensure that the product has a certain density and dimensional tolerance.The basic requirements of injection molding are plasticization, injection and molding.Plasticization is the prerequisite to achieve and ensure the quality of the molded products, and in order to meet the requirements of molding, the injection must be guaranteed to have enough pressure and speed.At the same time, because the injection pressure is very high, the pressure in the mold cavity is correspondingly very high (the average pressure in the mold cavity is generally between 20~45MPa), so there must be enough mold closing force.Thus it can be seen that the injection device and the joint mould device are the key parts of the injection molding machine.

The evaluation of plastic products mainly has three aspects. 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 corresponding physical properties, chemical properties, electrical properties and so on.These quality requirements also vary according to the use of the products, the scale of the requirements are also different.The defects of the products mainly lie in the design, manufacturing precision and wear degree of the mold.But in fact, the plastic processing plant technicians often suffer from the problem of using process means to make up for the mold defects and ineffective difficult situation.

The adjustment of technology in the process of production is a necessary way to improve the quality and output of products.Due to the injection cycle itself is very short, if the process conditions are not well mastered, the waste will be endless.When adjusting the process, it is better to change only one condition at a time and observe it several times. If the pressure, temperature and time are all adjusted together, confusion and misunderstanding will be easily caused and the reason why there is a problem is unknown.The measures and means to adjust the process are various.For example, there are more than ten possible ways to solve the problem of product note dissatisfaction. Only by selecting one or two major solutions to solve the crux of the problem can the problem be really solved.In addition, attention should be paid to the dialectical relationship in the solution.For example: the product appeared concave, sometimes to increase the material temperature, sometimes to reduce the temperature;Sometimes it is necessary to increase the quantity, sometimes it is necessary to reduce the quantity.Acknowledge the feasibility of reverse solutions to the problem.