Classification and characteristics of injection molding machine hydraulic station
1. Working principle
The working principle of the injection molding machine is similar to the syringe used for injection. It uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (that is, the viscous fluid state) into the closed mold cavity. The process of obtaining the product after curing and shaping.
Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding-melting and plasticizing-pressure injection-mold filling and cooling-mold opening and picking. After taking out the plastic part, the mold is closed again for the next cycle.
Injection molding machine operation project: The injection molding machine operation project includes three aspects: control keyboard operation, electrical control system operation and hydraulic system operation. Carry out the injection process action, feeding action, injection pressure, injection speed, ejection type selection, temperature monitoring of each section of the barrel, injection pressure and back pressure adjustment, etc.
The molding process of a general screw injection molding machine is as follows: first add granular or powdered plastic into the barrel, and make the plastic into a molten state through the rotation of the screw and heating of the outer wall of the barrel, and then the machine closes the mold and moves the injection seat forward. Make the nozzle close to the gate of the mold, and then pass pressure oil into the injection cylinder to push the screw forward, thereby injecting the melt into the closed mold with a lower temperature at a high pressure and a faster speed. Time and pressure hold (also known as holding pressure), cooling to make it solidify and form, then the mold can be opened and the product can be taken out (the purpose of holding pressure is to prevent the backflow of the melt in the mold cavity, add materials to the mold cavity, and ensure the product Has a certain density and dimensional tolerances). The basic requirements of injection molding are plasticization, injection and molding. Plasticization is a prerequisite for realizing 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 correspondingly high pressure is generated in the cavity (the average pressure in the cavity is generally between 20 and 45 MPa), so there must be a sufficient clamping force. It can be seen that the injection device and the clamping device are the key components of the injection molding machine.
There are three main aspects to the evaluation of plastic products. The first is the appearance quality, including completeness, color, gloss, etc.; the second is the accuracy of the size and relative position; the third is the physical properties, chemical properties, and Electrical performance, etc. These quality requirements are different depending on the use occasions of the products, and the required scales are also different. The defects of the product mainly lie in the design of the mold, the manufacturing accuracy and the degree of wear. But in fact, the technicians of plastic processing plants often suffer from the difficult situation of using technological means to compensate for the problems caused by mold defects without great results.
The adjustment of the process in the production process is a necessary way to improve the quality and output of products. Because the injection cycle itself is very short, if the process conditions are not well mastered, there will be an endless stream of waste products. When adjusting the process, it is best to change only one condition at a time and observe a few more times. If the pressure, temperature, and time are adjusted together, it is easy to cause confusion and misunderstanding. If there is a problem, I don't know the reason. The measures and means to adjust the process are various. For example, there are more than a dozen possible solutions to solve the problem of product complaints. Only by choosing one or two main solutions to 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 the product has a depression, sometimes the material temperature must be increased, sometimes the material temperature must be lowered; sometimes the material quantity must be increased, and sometimes the material quantity must be reduced. It is necessary to recognize the feasibility of reversing measures to solve the problem.
(1) Classified by plasticization method
1. Plunger type plastic injection molding machine
It has poor mixing properties and poor plasticization properties, so a shunt shuttle device must be installed. Has been rarely used.
2. Reciprocating screw type plastic injection molding machine;
Relying on the screw for plasticization and injection, the mixing and plasticizing properties are very good, and the most used.
3. Screw-the plunger plastic injection molding machine relies on the screw for plasticization and the plunger for injection, the two processes are separated.
(2) Classified according to the way of clamping
Vertical injection molding machine
1. The injection device and the clamping device are on the same vertical centerline, and the mold is opened and closed in the up and down direction. Its floor space is only about half of that of a horizontal machine, so it is about twice as productive when converted into floor space.
2. Easy to realize insert molding. Because the surface of the mold faces upwards, it is easy to insert and position the insert. If the lower template is fixed and the upper template is movable, combined with a belt conveyor and a manipulator, fully automatic insert molding can be easily realized.
3. The weight of the mold is supported by the horizontal template to open and close up and down, and the phenomenon that the template cannot be opened and closed due to the gravity of the mold similar to the horizontal machine will not occur. It is conducive to maintaining the precision of machinery and molds for durability.
4. The cavity of each plastic part can be taken out by a simple manipulator, which is conducive to precision molding.
5. Generally, the surrounding mold clamping device is open, and it is easy to configure various automatic devices, which is suitable for the automatic molding of complex and delicate products.
6. The belt-drawing conveying device is easy to realize the installation through the middle of the mold, which is convenient to realize the automatic production of molding.
7. It is easy to ensure the resin fluidity in the mold and the consistency of the mold temperature distribution.
8. Equipped with rotating table, moving table and inclined table, etc., it is easy to realize insert molding and in-mold combination molding.
9. In the small batch trial production, the mold structure is simple, low cost, and easy to unload.
10. Having withstood the test of many earthquakes, the vertical machine has better seismic resistance than the horizontal machine due to its low center of gravity.
Horizontal injection molding machine
1. Even if it is a mainframe, due to its low body, there is no height limit for the plant to be installed.
2. When the product can fall automatically, automatic molding can be realized without using a manipulator.
3. Due to the low body, it is convenient to supply materials and easy to overhaul.
4. The mold needs to be installed by crane.
5. When multiple units are arranged side by side, the molded products can be easily collected and packaged by the conveyor belt.
Angle injection molding machine
The axis of the injection screw of the angle injection molding machine and the movement axis of the mold clamping mechanism are arranged perpendicular to each other, and its advantages and disadvantages are between the vertical and horizontal. Because the injection direction and the mold parting surface are on the same plane, the angle injection molding machine is suitable for molds with asymmetric geometry with side gates or products that do not allow gate marks in the molding center.
Two-color injection molding machine
An injection molding machine that can inject two colors at a time can meet consumers' appearance requirements and make users more comfortable using the product.
Injection molding machine multi-station molding machine
The injection device and the mold clamping device have two or more working positions, and the injection device and the mold clamping device can also be arranged in various ways.
Electric injection molding machine
The all-electric injection molding machine can not only meet the needs of special purposes, but also has more advantages than ordinary injection molding machines.
Another advantage of the all-electric injection molding machine is that it can reduce noise, which not only benefits the workers, but also reduces the investment and construction costs in the soundproof production workshop.