A fully electric injection molding machine is a processing injection molding machine that is fully powered by electricity. It can inject thermoplastics and process them into various molds. It is a commonly used machine in the process of chemical material synthesis.

Definition

Injection molding machine (abbreviated as injection machine or injection molding machine) is the main molding equipment that uses plastic molding molds to make plastic products of various shapes from thermoplastics or thermosetting materials.

Injection molding is achieved through injection molding machines and molds.

Types

Injection molding machines are of three types: vertical, horizontal, and fully electric. However, no matter which type of injection molding machine, it has two basic functions:

(1) heating the plastic to make it melt;

(2) applying high pressure to the molten plastic to make it eject and fill the mold cavity.

Structure and function

Injection molding machines are usually composed of injection systems, mold clamping systems, hydraulic transmission systems, electrical control systems, lubrication systems, heating and cooling systems, safety monitoring systems, etc.

(1) Injection molding system

The function of the injection system: The injection system is one of the most important components of the injection molding machine. Generally, there are three main types: plunger type, screw type, and screw pre-plastic plunger injection type. The most widely used type is the screw type. Its function is to heat and plasticize a certain amount of plastic within a specified time in one cycle of the injection molding machine, and then inject the molten plastic into the mold cavity through the screw at a certain pressure and speed. After the injection is completed, the molten material injected into the mold cavity is kept in shape.

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

The plasticizing device of the screw injection molding machine is mainly composed of a feeding device, a barrel, a screw, and a nozzle. The power transmission device includes an injection cylinder, an injection seat moving cylinder, and a screw drive device (melt motor).

(2) Clamping system

The function of the clamping system: The function of the clamping system is to ensure the closing, opening, and ejection of the mold. At the same time, after the mold is closed, sufficient clamping force is provided to the mold to resist the cavity pressure generated by the molten plastic entering the mold cavity, prevent the mold from opening, and cause the product to be in a bad state.

Composition of the mold clamping system: The mold clamping system is mainly composed of a mold clamping device, a mold adjustment mechanism, an ejection mechanism, front and rear fixed templates, a mobile template, a mold clamping cylinder and a safety protection mechanism.

(3) Hydraulic system

The function of the hydraulic transmission system is to provide power for the various actions required by the injection molding machine according to the process, and to meet the pressure, speed, temperature and other requirements of each part of the injection molding machine. It is mainly composed of various hydraulic components and hydraulic auxiliary components, among which the oil pump and motor are the power sources of the injection molding machine. Various valves control the oil pressure and flow to meet the various requirements of the injection molding process.

(4) Electrical control system

The electrical control system and the hydraulic system are reasonably coordinated to achieve the process requirements (pressure, temperature, speed, time) and various program actions of the injection molding machine. It is mainly composed of electrical appliances, electronic components, instruments, heaters, sensors, etc. There are generally four control modes: manual, semi-automatic, fully automatic, and adjustable.

(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, which is installed on the outside of the barrel and detected in sections by thermocouples. The heat is conducted through the barrel wall to provide a heat source for the plasticization of the material; the cooling system is mainly used to cool the oil temperature. Excessive oil temperature will cause a variety of faults, so the oil temperature must be controlled. Another location that needs cooling is near the discharge port of the material pipe to prevent the raw material from melting at the discharge port, resulting in the failure of the raw material to be discharged normally.

(6) Lubrication System

The lubrication system is a circuit that provides lubrication conditions for the relative moving parts of the injection molding machine, such as the moving plate, mold adjustment device, and connecting rod hinge, so as to reduce energy consumption and increase the life of parts. Lubrication can be regular manual lubrication or automatic electric lubrication;

(7) Safety protection and monitoring system

The safety device of the injection molding machine is mainly used to protect the safety of people and machines. It is mainly composed of safety doors, hydraulic valves, limit switches, photoelectric detection elements, etc., to achieve electrical-mechanical-hydraulic interlocking protection.

The monitoring system mainly monitors the oil temperature, material temperature, system overload, and process and equipment failures of the injection molding machine, and indicates or alarms when abnormal conditions are found.

Fourth, the working principle and mode of the injection molding machine:

The working principle of the injection molding machine is similar to that of the syringe used for injection. It uses the thrust of the screw (or plunger) to inject the plasticized molten state (i.e., viscous flow state) plastic into the closed mold cavity, and obtains the product after solidification and finalization.

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

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

The molding process of a general screw injection molding machine is: first, granular or powdered plastic is added to the barrel, and the plastic is molten by rotating the screw and heating the outer wall of the barrel. Then the machine closes the mold and moves the injection seat forward, so that the nozzle is close to the gate of the mold. Then, pressurized oil is passed into the injection cylinder to push the screw forward, so that the molten material is injected into the closed mold with a lower temperature at a very high pressure and a faster speed. After a certain period of time and pressure maintenance (also known as pressure holding), cooling, it is solidified and formed, and the mold can be opened to take out the product (the purpose of pressure holding is to prevent the backflow of the molten material in the mold cavity, to add materials to the mold 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 for achieving 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 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 a sufficiently large clamping force. It can be seen that the injection device and the clamping device are key components of the injection molding machine.

There are three main aspects of the evaluation of plastic products. The first is the appearance quality, including integrity, color, gloss, etc.; the second is the accuracy between the size and relative position; the third is the physical properties, chemical properties, electrical properties, etc. corresponding to the purpose. These quality requirements are different according to the different occasions of the product. The defects of the product mainly lie in the design, manufacturing accuracy and degree of wear of the mold. But in fact, the technicians of the plastic processing plant often suffer from the difficult situation of using process means to make up for the problems caused by the defects of the mold without much effect.

The adjustment of the process in the production process is a necessary way to improve the quality and output of the product. Since the injection molding cycle itself is very short, if the process conditions are not well controlled, there will be an endless supply of waste products. When adjusting the process, 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 it is unknown why a problem occurs. There are many measures and means to adjust the process. For example, there are more than a dozen possible solutions to the problem of insufficient injection of products. Only by selecting 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, if a product has a dent, sometimes the material temperature should be increased, sometimes it should be lowered; sometimes the material amount should be increased, and sometimes it should be reduced. The feasibility of solving problems with reverse measures should be recognized.