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русскийThe working principle of a rubber mixing mill is as follows:
Rubber mixing mill is a key equipment used for mastication and mixing of rubber in rubber processing. Its core function is to shear, extrude and mix rubber through mechanical force, so that the rubber can reach the required plasticity or uniform mixing state. The following is a detailed explanation from the aspects of basic structure and working principle:
I. Basic Structure
Rubber mixing mill (taking the open rubber mixing mill as an example, which is the most common and typical in principle) is mainly composed of the following core components:
- Rollers: A pair of parallel cylindrical metal rollers (usually made of steel, with smooth surface or special patterns), which are the core working parts of rubber mixing. The two rollers can rotate in the same direction (rarely seen) or in opposite directions (mainstream design), and their rotating speeds are different (there is a speed ratio, usually 1:1.2 ~ 1:1.5).
- Frame: A frame that supports the rollers, transmission device and other components to ensure the stability of the equipment.
- Transmission system: Composed of motor, reducer, gear, etc., it provides rotating power for the rollers and controls the rotating speed and speed ratio.
- Adjusting device: Used to adjust the distance between the two rollers (roll spacing) to control the pressure and shearing force on the rubber.
- Heating/cooling system: The inside of the rollers of some rubber mixing mills is equipped with channels, through which steam, hot water or cold water can be introduced to adjust the temperature of the rollers (for example, heating is needed to soften the rubber during mastication, and cooling may be needed during mixing to prevent overheating).
II. Working Principle
The core of the rubber mixing mill is to use the relative movement of the rollers to generate mechanical force on the rubber. The specific process is as follows:
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Feeding and clamping
Put rubber raw materials (such as natural rubber blocks, synthetic rubber particles) between the two rollers. Due to the opposite rotation of the rollers and the existence of speed difference, the rubber will be brought into the gap between the rollers by friction (i.e., "biting in"). The smaller the roll spacing, the greater the clamping force on the rubber. -
Shearing and stretching
Because the rotating speeds of the two rollers are different (for example, the front roller is fast and the rear roller is slow), when the rubber passes through the roll gap, the part in contact with the fast roller is driven to accelerate, while the part in contact with the slow roller moves slowly, resulting in strong shear deformation inside the rubber; at the same time, the rubber is squeezed and stretched by the rollers, resulting in tensile deformation.
This shearing and stretching effect will break the entanglement between rubber molecular chains, causing the molecular chains to break or disperse, thereby reducing the elasticity of the rubber (improving plasticity, i.e., the purpose of "mastication"), or making the compounding agents (such as carbon black, sulfur, accelerators, etc.) evenly dispersed into the rubber (i.e., the purpose of "mixing"). -
Refining and mixing
In actual operation, the rubber will form a "rubber package" (a rubber layer around the surface of the roller) on the roller. The operator needs to tear off the rubber package from the roller manually or by mechanical devices, fold it, turn it over and then feed it into the roll gap again (i.e., "refining").
This process allows different parts of the rubber to pass through the roll gap repeatedly, ensuring that all areas are subject to uniform shearing and extrusion, and finally making the overall performance of the rubber consistent (uniform plasticity during mastication, uniform dispersion of compounding agents during mixing). -
Auxiliary role of temperature control
The mechanical force will cause friction heat inside the rubber, and the temperature rise may lead to rubber aging (such as natural rubber is easy to degrade when overheated). Therefore, the temperature is controlled by the heating/cooling system of the rollers:- During mastication, proper heating can soften the rubber, reduce the force between molecular chains, and assist the shearing effect;
- During mixing, cooling can prevent the rubber from vulcanizing in advance due to overheating (such as cooling is needed after adding sulfur), and at the same time prevent the compounding agents from decomposing due to high temperature.
III. Supplementary Notes
In addition to the open rubber mixing mill, there is also a closed rubber mixing mill (such as internal mixer), whose principle is similar but the structure is more complex: the rubber is extruded and sheared by the rotor (a rotating part similar to a roller) and the chamber wall in the closed mixing chamber, which has higher efficiency and less dust pollution, but the core still relies on the shearing and mixing effect of mechanical force.
In short, the rubber mixing mill generates shearing, extrusion and stretching forces through the relative movement of the rollers (or rotors), combined with temperature control and operating technology, to realize the mastication or mixing of rubber, laying a foundation for the forming of subsequent rubber products (such as tires, sealing rings).
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