Know: "Injection molding machine"

Injection molding machine, also known as injection molding machine or injection machine. It is the main molding equipment for making plastic products of various shapes from thermoplastic plastics or thermosetting materials using plastic molding dies. Divided into vertical, horizontal, all-electric. The injection molding machine can heat the plastic, apply high pressure to the molten plastic, and eject it to fill the mold cavity.

Injection molding machine structure and function

Injection molding machines usually consist of injection systems, mold clamping systems, hydraulic transmission systems, electrical control systems, lubrication systems, heating and cooling systems, and safety monitoring systems. [1]

(1) injection system

The role of the injection system: injection system is one of the most important components of the injection molding machine, there are generally three kinds of plunger type, screw type, screw pre-molding plunger injection type. The most widely used at present is the screw type. Its role is that in a cycle of the injection molding machine, a certain amount of plastic can be plasticized in a prescribed time, and the molten plastic is injected into the mold cavity by a screw under a certain pressure and speed. At the end of the injection, the molten material injected into the mold cavity remains fixed.

The composition of the injection system: The injection system consists of a plasticizing device and a power transmission device.

Screw plastic injection molding machine plasticizing device is mainly composed of feeding device, barrel, screw, nozzle part. The power transmission device includes an injection cylinder, an injection station moving cylinder, and a screw driving device (melting motor).

(2) Clamping system

The function of the mold clamping system: The function of the mold clamping system is to ensure that the mold is closed, opened and ejected. At the same time, after the mold is closed, a sufficient clamping force is given to the mold to resist the pressure of the mold cavity generated by the molten plastic entering the mold cavity to prevent the mold from opening, resulting in a defective product.

The composition of the mold clamping system: The mold clamping system consists of a mold clamping device, a mold adjustment mechanism, an ejector mechanism, a front and rear fixed mold, a movable mold, a mold clamping cylinder, and a safety protection mechanism.

(3) Hydraulic system

The role of the hydraulic transmission system is to achieve the injection molding machine to provide power according to the various actions required by the process, and to meet the pressure, speed, temperature and other requirements of the injection molding machine parts. It is mainly composed of its own kinds of hydraulic components and hydraulic auxiliary components, in which the oil pump and the motor are the power source of the injection molding machine. Various valves control the oil pressure and flow to meet the requirements of the injection molding process.

(4) Electrical Control System

The electrical control system and the hydraulic system are properly matched to realize the process requirements (pressure, temperature, speed, time) and various types of injection machines.

Principle schematic program action. Mainly by the electrical appliances, electronic components, meters, heaters, sensors and other components. There are generally four control methods, manual, semi-automatic, automatic, and adjustment.

(5) Heating/cooling system

The heating system is used to heat the barrel and the injection nozzle. The barrel of the injection molding machine generally uses an electric heating coil as a heating device, is installed outside the barrel, and is detected by a thermocouple segment. Heat through the cylinder wall heat to provide material for the plasticization of the material; cooling system is mainly used to cool the oil temperature, oil temperature is too high will cause a variety of failure 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 raw material from melting at the feed port, resulting in the raw material being not properly fed.

(6) Lubrication system

Lubrication system is the loop of the injection molding machine's moving platen, mold adjustment device, connecting rod hinge, etc. to provide lubrication conditions in order to reduce energy consumption and improve component life. Lubrication can be periodic manual lubrication, or it can be Automatic electric lubrication;

(7) Security Protection and Monitoring System

The safety device of the injection molding machine is mainly used to protect human and machine safety devices. It is mainly composed of safety gates, hydraulic valves, limit switches, and photoelectric detection elements to realize electrical-mechanical-hydraulic interlock protection.

The monitoring system mainly monitors the oil temperature, material temperature, system overload, and process and equipment failures of the injection molding machine and finds abnormal conditions to indicate or alarm.

Injection molding machine working principle and mode:

The working principle of an injection molding machine is similar to that of a syringe used for injection. It uses the force of a screw (or plunger) to inject a plasticized molten state (ie, viscous flow state) into a closed mold cavity. After curing and setting, the process of the product is obtained.

Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding - melt plasticization - pressure injection - mold cooling - mold removal. Remove the plastic parts and then close the mold for the next cycle.

Injection molding machine operation items: Injection molding machine operation items include control of the keyboard operation, electrical control system operation and hydraulic system operation in three aspects. The injection process, the feeding action, the injection pressure, the injection speed, the ejection type selection, the temperature monitoring of each barrel section, the injection pressure, and the back pressure adjustment were performed.

The general molding process of the screw-type injection molding machine is as follows: First, the granular or powdery 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 the machine then performs mold clamping and injection seat advancement. The nozzle is tightly attached to the gate of the mold, and then the pressure oil is injected into the injection cylinder to advance the screw so that the molten material is injected into the closed mold with a relatively low temperature and a relatively high speed. The time and pressure are maintained (also known as pressure holding), cooling, solidifying and molding, then the product can be opened and removed from the product (the purpose of maintaining the pressure is to prevent the backflow of the molten material in the cavity, to supplement the material in the cavity, and to protect

Universal horizontal injection molding machine certification products have a certain density and dimensional tolerances). The basic requirements for injection molding are plasticization, injection and molding. Plasticization is the prerequisite for achieving and ensuring the quality of molded products. 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 very high pressure is generated in the mold cavity (the average pressure in the mold cavity is generally between 20 and 45 MPa), so a sufficient clamping force must be provided. It can be seen that the injection device and the mold clamping device are key components of the injection molding machine.

The evaluation of plastic products mainly includes three aspects. The first is the appearance quality, including the integrity, color, luster, etc.; the second is the accuracy between the size and relative position; the third is the physical and chemical properties corresponding to the purpose. Electrical properties. These quality requirements, in turn, vary depending on the use of the product. The defects of the products mainly lie in the design, manufacturing precision and wear degree of the molds. In fact, technicians in plastic processing plants often suffer from the difficulty of using technical means to make up for the problems caused by mold defects and have little effect.

The adjustment of the process in the production process is a necessary way to improve the quality and yield of the product. Because the injection cycle itself is very short, if the process conditions are not well mastered, waste products will continue to flow. When adjusting the craft, it is best to change only one condition at a time and observe several times at a time. If pressure, temperature, and time are unified and adjusted, it is easy to cause confusion and misunderstanding. If problems arise, you do not know what the reason is. The measures and means for adjusting the process are various. For example, there are more than a dozen possible solutions to solve the problem of unsatisfactory products. To solve the problem, one or two major solutions must be selected to solve the problem. In addition, we should also pay attention to the dialectical relationship in the solution. For example: The product has sunken, sometimes to raise 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 admit the feasibility of solving the problem with reverse measures.