Structure function and working principle of injection molding machine


Injection molding machine is also known as injection molding machine or injection machine, many factories called beer (pijī), injection products called beer parts. It is the thermoplastic plastic or thermosetting materials using plastic molding mold into plastic products of various shapes of the main molding equipment. According to the arrangement of injection device and mold locking device, injection molding machine can be divided into vertical, horizontal and vertical and horizontal compound

Structure function


zy-623 injection molding machine is usually composed of injection system, die closing system, hydraulic transmission system, electrical control system, lubrication system, heating and cooling system, safety monitoring system, etc.

The injection system

The role of injection system: Injection system is one of the most important parts of injection molding machine, generally has plunger type, screw type, screw premolded plunger injection type three main forms. The most widely used is the screw type. Its function is that in a cycle of the plastic injection machine, a certain amount of plastic can be heated and plasticized within a specified time, and the molten plastic can be injected into the mold cavity through the screw under a certain pressure and speed. After injection, the molten material injected into the mold cavity is kept in shape.

Injection system composition: Injection system is composed of plasticizing device and power transmission device.
The plasticizing device of the screw injection molding machine is mainly composed of a feeding device, a cylinder, a screw, a gluing assembly and a nozzle. The power transmission device includes injection cylinder, injection seat moving cylinder and screw drive device (glue motor).

The clamping system

The function of the die closing system: The function of the die closing system is to ensure that the die is closed, opened and pushed out. At the same time, after the mold is closed, the mold is provided with enough clamping force to resist the pressure of the mold cavity generated by the molten plastic into the mold cavity, and prevent the mold from opening, resulting in the bad status of the product.

The composition of the die closing system: The die closing system is mainly composed of the die closing device, the machine stranding, the die adjusting mechanism, the ejection mechanism, the front and back fixed template, the moving template, the die closing cylinder and the safety protection mechanism.

The hydraulic system

The function of hydraulic transmission system is to realize the injection molding machine according to the requirements of the process of various actions to provide power, and meet the requirements of pressure, speed, temperature and other parts of the injection molding machine. It is mainly composed of their own hydraulic components and hydraulic auxiliary components, oil pump and motor are the power source of injection molding machine. Various valves control oil pressure and flow to meet the requirements of injection molding process.

Electrical control

The electrical control system and the hydraulic system can be reasonably coordinated to realize the technical process requirements (pressure, temperature, speed, time) and various program actions of the injection machine. It is mainly composed of electrical appliances, electronic components, instruments (as shown in "Instrument", heaters, sensors, etc. Generally, there are four control modes, manual, semi-automatic, automatic, adjustment.


The heating system is used to heat the cylinder and injection nozzle. The cylinder of injection molding machine generally adopts electric heating ring as the heating device, which is installed on the outside of the cylinder and tested by thermocouple. Heat conduction through the cylinder wall provides heat source for material plasticization; The cooling system is mainly used to cool the oil temperature. Too high oil temperature will cause a variety of faults, so the oil temperature must be controlled. The other place that needs cooling is near the feeding port of the feed pipe to prevent the feeding port of raw materials from melting, resulting in the normal feeding of raw materials.

Lubrication system

The lubrication system is a circuit to provide lubrication conditions for the parts with relative motion at the moving template, die adjusting device, connecting rod machine hinge and injection table of injection molding machine, so as to reduce energy consumption and improve the life of parts. Lubrication can be regular manual lubrication or automatic electric lubrication.

Safety monitoring

The safety device of injection molding machine is mainly used to protect the safety of people and machines. Mainly composed of safety door, safety baffle, hydraulic valve, limit switch, photoelectric detection components, etc., to achieve electrical - mechanical - hydraulic interlock protection.
The monitoring system mainly monitors the oil temperature, material temperature, system overload, process and equipment failure of injection molding machine, and indicates or alarms when abnormal conditions are found.

The working principle of

The working principle of the injection molding machine is similar to the syringe used for injection. It is a process of injecting the plastic in the melted state (viscous flow state) into the closed mold cavity with the help of the thrust of the screw (or plunger), and obtaining the product after curing and shaping.

Injection molding is a cycle process, each cycle mainly includes: quantitative feeding - melting plasticization - pressure injection - mold cooling - mold opening parts. After taking out the plastic parts, the mold is closed again for the next cycle.

Operation of injection molding machine: Operation of injection molding machine includes three aspects: control keyboard operation, electrical control system operation and hydraulic system operation. The SELECTION OF INJECTION process action, feeding action, injection pressure, injection speed, ejection type, temperature monitoring of each section of the barrel, injection pressure and back pressure regulation, 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 to maintain (also known as pressure preservation), cooling, so that its curing molding, can open the mold out of the product (the purpose of pressure preservation is to prevent the mold cavity melt reflux, to mold cavity replenishment materials, and ensure that the product has a certain density and size tolerance).

The basic requirements of injection molding are plasticization, injection and molding. Plasticizing is the prerequisite to achieve and ensure the quality of molding products, and in order to meet the requirements of molding, injection must ensure enough pressure and speed. At the same time, because the injection pressure is very high, the corresponding high pressure in the mold cavity (the average pressure in the mold cavity is generally between 20~45MPa), so there must be enough clamping force. It can be seen that the injection device and the combination mold 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, luster and so on; The second is accuracy between size and relative position; The third is the corresponding physical properties, chemical properties, electrical properties and so on. These quality requirements and according to the product use of different occasions, the requirements of the scale is different. The defects of the products mainly lie in the design, manufacturing accuracy and wear degree of the die. But in fact, the technical personnel of plastic processing plants often suffer from the difficult situation of making up for the problems caused by mold defects with technological means.

The regulation of technology in the production process is a necessary way to improve product quality and yield. Because the injection molding cycle itself is very short, if the process conditions are not well mastered, the waste will be endless. 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 is easy to cause confusion and misunderstanding. If there is a problem, I do not know what the reason is. The measures and means to adjust the technology are manifold. 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: products appear depression, sometimes to improve the material temperature, sometimes to reduce the material temperature; Sometimes to increase the amount of material, sometimes to reduce the amount of material. It is necessary to acknowledge the feasibility of reverse measures to solve the problem.