Injection molding is a very common plastic molding method. In order to better understand the injection molding, this paper summarizes the molding process of injection molding machine and general plastics, and shares the following contents:
about injection molding machine
Injection molding machine, also known as injection molding machine or injection machine, many factories called beer Ji, injection products called beer parts. It is the main molding equipment for making thermoplastic or thermosetting plastics into various shapes of plastic products by plastic molding mold. The injection molding machine heats the plastic and applies high pressure to the molten plastic to make it shoot out and fill the mold cavity.
Ningbo in Zhejiang and Dongguan in Guangdong have become important injection molding machine production bases in China and even in the world.
The following is a detailed explanation
1、 According to the shape of injection molding machine classification
According to the arrangement of injection device and mold locking device, it can be divided into vertical, horizontal and vertical horizontal compound.
a. Vertical injection molding machine
1. The injection device and the mold locking device are located on the same vertical center line, and the mold is opened and closed along the up and down direction. Its floor area is only about half of that of the horizontal machine, so the productivity is about twice of the floor area.
2. It is easy to realize insert molding. Because the mold surface is upward, it is easy to insert and position the insert. If the lower template is fixed and the upper template is movable, and the belt conveyor is combined with the manipulator, the automatic insert molding can be easily realized.
3. The weight of the die is supported by the horizontal template, and the opening and closing action will not occur, which is similar to that of the horizontal machine due to the gravity of the mold, which makes the template unable to open and close. It is beneficial to maintain the accuracy of the machine and the mold.
4. The cavity of each plastic part can be taken out by a simple manipulator, which is conducive to precision molding.
5. Generally, the mold locking device is open and easy to configure all kinds of automatic devices, which is suitable for the automatic forming of complex and exquisite products.
6. The belt conveyor is easy to be installed in the middle of the mold in series, which is convenient to realize automatic molding production.
7. It is easy to ensure the consistency of resin fluidity and mold temperature distribution in the mold.
8. Equipped with rotary table, mobile table and inclined table, it is easy to realize insert molding and in mold combination molding.
9. In small batch trial production, the die structure is simple, the cost is low, and it is easy to unload.
10. It has been tested by many earthquakes. Because of its low center of gravity, the vertical machine has better seismic performance than the horizontal machine.
b. Horizontal injection molding machine
1. Even for the large-scale machine, due to its low fuselage, there is no height limit for the installed workshop.
2. When the product can fall down automatically, it can be formed automatically without using a manipulator.
3. Because of the low fuselage, it is convenient to feed and repair.
4. The mould needs to be installed by crane.
5. When several sets are arranged side by side, the molded products are easy to be collected and packaged by the conveyor belt.
c. Angle injection molding machine
The axis of the injection screw of the angular injection molding machine and the moving axis of the mold closing mechanism template are arranged vertically with each other. Because the injection direction and the parting surface of the mold are in the same plane, the angular injection molding machine is suitable for the unsymmetrical geometric shape of the side gate or the products with no gate trace in the molding center.
d. Multi station molding machine
The injection device and mold closing device have two or more working positions, and the injection device and mold closing device can also be arranged in a variety of ways.
2、 According to the power source classification of injection molding machine
a. Mechanical manual injection molding machine
At the beginning, injection molding machine appeared in the form of manual and mechanical operation. In the early stage of the last century, the injection molding machine was just invented. The clamping mechanism and injection mechanism all use the lever principle to produce the clamping force and injection pressure, which are also the basis of modern elbow clamping mechanism.
b. Hydraulic injection molding machine
With the development of industrial technology, especially the development of hydraulic control technology, the mechanical injection molding machine with manual operation can not meet the requirements of production.
The hydraulic injection molding machine has the advantages of convenient operation speed, easy pressure control and high mold locking pressure (the largest clamping force injection molding machine in the world is 8000 tons, and the minimum consistent minimum locking force injection molding machine is 5 tons). The control is accurate and can meet the needs of special purposes. This is also the main reason why the hydraulic injection molding machine has been renewed for a long time. From the current development point of view, in the future for a long time, hydraulic injection molding machine will occupy the main place.
Each action of the injection molding machine is controlled by controlling the flow rate, pressure and direction of the hydraulic power source.
c. Pneumatic injection molding machine
Pneumatic injection molding machine is a desktop injection molding machine with compressed air as power and hydraulic cylinder as executive component. It not only has the characteristics of low energy consumption and light equipment of pneumatic system, but also has high stability and controllability of hydraulic equipment. The main features are as follows:
1. Due to the power of compressed air, there is no pollution to the environment and no noise. One air compression pump station can drive multiple pneumatic injection molding machines to work at the same time. The maintenance of the equipment is simpler and cheaper.
2. The equipment adopts special pneumatic and hydraulic transmission system. The controllable pressure of the equipment is as high as 400kg / cm2. The special performance of its structure and power can make the design of the equipment light and miniaturized. It is especially suitable for the production of high-precision products with an output less than 15g, such as audio-visual, DC power supply, charger, communication, network device connector and other hardware and plastic accessories. The working mode of the traditional hand pushing movable die is not changed, and the efficiency is increased by 20%.
3. The feeding and injection system adopts built-in self rotating screw melting glue and plunger injection structure. Compared with screw type hydraulic injection molding machine, the operation is simpler, and the molding effect and precision are better. The unique barrel and screw design can perfectly solve the problem of heat stability and color change of environment-friendly and low-toxic plastics, and completely eliminate the damage of screw to molecular structure in engineering plastic melting and the trouble of plastic compression ratio equipment when feeding.
4. Due to the miniaturization of the equipment, energy saving and environmental protection, the production layout of the workshop can be arranged as an assembly line, which can double the efficiency of the traditional production layout and save more than 1 / 5 of the human resources.
d. Electric injection molding machine
Compared with the traditional full hydraulic injection molding machine, all electric injection molding machine completely abandons the oil pressure drive system produced by the oil pump motor of the full oil pressure machine in the power drive system, and adopts the servo motor (servo motor) The control precision of the power system of injection molding machine is greatly improved, and the pollution problem of hydraulic oil to the environment is completely solved, and the noise generated by machinery is also reduced.
All electric injection molding machine has the advantages of energy saving, environmental protection, low noise, accurate measurement, etc. the control system of all electric injection molding machine is simpler than that of oil press, the reaction is also rapid, it has excellent control precision, can provide complex synchronous action and shorten the production cycle; However, due to the limitation of transmission mechanism and cost control, it is not suitable for super large high injection molding machine.
3、 Classification according to plasticizing method
1) Plunger type plastic injection molding machine: mixing is very poor, plasticization is not good, to install a shunt shuttle device. It has been rarely used.
2) Reciprocating screw type plastic injection molding machine: depending on screw for plasticizing and injection, the mixing and plasticizing properties are very good, now it is most used.
3) Screw plunger plastic injection molding machine: plasticizing by screw and injection by plunger are separated.
4) According to the mode of mold closing
1. Elbow bending
At present, there is no patent barrier for the most used one. After a long time of testing, it is the cheapest, simple and reliable mode of mold closing.
2. Direct pressure type
Single or multiple hydraulic cylinders are used to directly act on the mold to produce clamping force.
Advantages: accurate control of clamping force, good protection of mold, no influence on the parallelism of template due to mechanical wear. It is suitable for mould with high requirement.
Disadvantages: the energy consumption is higher than the elbow type, and the structure is complex.
3. Two plates
By changing the force length of coring column to adjust the position of high-pressure mold locking, so as to cancel the tail plate structure used for mold adjustment. It is generally composed of mold opening and closing cylinder, moving template, fixed template, high-pressure oil cylinder, coring column locking device, etc. The opening and closing die is directly driven by the oil cylinder to reduce the mechanical parts.
Advantages: high speed of mold adjustment, large mold thickness, small mechanical wear and long service life.
Disadvantages: high cost, complex control and high maintenance difficulty. It is generally used for super large machines.
4. Compound type
The combination types of curved elbow type, straight pressing type and two plate type.
