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Application of plastic in rolling bearings (5)
Source: China Bearing Network Time: 2014-02-19
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Usually the coefficient of conflict of the data. Uniformity. The condition of self-smoothness is the cohesive force between the molecules. The swell of the singularity of the scorpion. The other smooth function is related to the smooth condition.
From the point of view of wear resistance; UHMWPE, PA, POM, PTFE and other resins are superior to carbon steel and brass.
In order to reduce the coefficient of conflict and wear of the resin; in addition to the resin with a small coefficient of conflict; improve the smooth conditions; can also be filled with wear-resistant filler in the resin; such as PTFE, UHMWPE, graphite, MoS2, smooth oil, bronze powder, etc. Use GF, CF and other fibers to enhance a series of modification methods.
The PV value of the PV value is an important goal to indicate the relationship between pressure and velocity between moving parts. The critical PV value is the dry conflict of plastic and related cover sliding bearings and the limit of pressure (load) or speed when oil is smooth. It determines the wear resistance of the data; it is the constraint on the life of the product or the operating temperature of the product; this value is proportional to the conflicting power loss; it characterizes the heating element of the bearing. The intent to constrain the PV value is to constrain the temperature rise; Avoid bearing temperature rise and excessive gluing damage.
The size of the PV value is related to the function of the matrix of the resin, the conflicting target, the smooth condition and the operating temperature, etc. For example, the critical PV value when the POM is matched with each other is 0. 04-0. 09 MPa. m/s; after self-smoothing modification; critical PV value can reach 0. 196 MPa. m/s; while POM is combined with 45# steel; the critical PV value can be as high as 0. 392-0. 588 MPa?m/s. The PV value of the PTFE-based nanocomposite data can reach 1.42-1.49 MPa. m / s; the application temperature can reach 230 ° C. Different resins at the same speed; PV values ​​are not the same at different temperatures, the same resin; PV values ​​are not the same at different temperatures.
PEEK is especially CF enhanced grade; at 200 ° C; V = 183m / min, its PV value can reach 60MPa?m / min; and the coefficient of conflict is small, the wear rate is low; therefore its application in the bearing is very obvious. GF And CF enhanced PEEK heat distortion temperature up to 315 ° C; long-term operating temperature up to 250-260 ° C, showing excellent wear resistance, self-smooth under various pressure, speed, temperature and original roughness; It is suitable for working conditions with low conflict coefficient and severe wear resistance.
PEEK is resistant to gamma ray radiation and chemical peeling; fatigue resistance is the best of any resin. It can be used in steam or high pressure water over 250 ° C for hundreds of hours without significant changes in function. PEEK provides a great data advantage in aerospace; plastic bearings used in aviation and special conditions.
PA66/GF usually uses temperature not exceeding 120 °C; for some corrosive media such as ammonia used as refrigerant in compressors; it can not be used at operating temperatures above 70 °C. SKF company in the cage Use PEEK/GF; use a communication motor or transformer that satisfies the high speed; chemical corrosion or high temperature.
The total return; should be based on the critical PV value, the temperature rise of the resin, the conditions of the operating conditions to properly select the type of plastic used in the bearing.
Do a good job of energy saving and emission reduction. Even in the metal structure of the bearing used plastic cage; in order to further reduce the conflict; still use smoothing agent; and once the internal smoothing agent is used up; its life is announced. For the bearing life The most important thing is during the start-up period; during the initial operation; because the smooth film is not formed; the bearing is often in the dry state; if the bearing is smooth from the beginning of the operation; this can deal with the problem of smooth film hysteresis.
American Igus series plastic bearings do not need to add smoothing agent; complete environmental protection; the solid smoothing agent inside the polymer bearing can also reduce the bearing quality; reduce the consumption of fuel and smoothing agent together; reduce the carbon dioxide emissions.
From this point of view; the polymer used to make the bearing parts should be modified as necessary; to deal with the problem of smooth film lag; reach as little as possible or even industrial smoothing agent; complete energy saving and emission reduction.
It is determined that plastics have their characteristics; they can be and have been used in bearings after appropriate and necessary modification.
The application of plastic in the inner and outer rings of the bearing has been steadily developed, and its application on the rolling body should be treated with caution according to the specific conditions.
According to the critical PV value; conflict wear characteristics and various plastic properties; reasonable choice of application. The current PEEK / CF (or GF) features the most outstanding.
When plastic is used on bearings; pay attention to the harmony of skill, economic feasibility and environmental protection.
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