Knowledge
Technical Guide: Sliding Bearing Application Examples
Classification of sliding bearings: plastic bearings, graphite bearings, electromagnetic bearings, liquid dynamic pressure bearings, gemstone bearings, gas bearings, etc. Different bearings have their own advantages, disadvantages, and application scenarios. The following mainly introduces some widely used sliding bearings.
1. Plastic bearings
Friction components such as bearings, guide rails, piston rings, etc. are commonly made of plastic, such as water pump bearings, rolling mill bearings, stern bearings, etc. Especially, non lubricated bearings can be made of plastic. Stamping polytetrafluoroethylene sheets into lip seals, bearing shells, piston rings, and gaskets has been successfully applied to equipment such as belt conveyors, typewriters, sewing machines, record players, water pumps, textile machinery, and agricultural machinery.
Plastic has the characteristics of light weight, insulation, friction reduction, wear resistance, self-lubricating, corrosion resistance, simple molding process, and high production efficiency. Compared with metal materials, their tribological properties are sensitive to environmental temperature and humidity, exhibit significant characteristics related to viscoelasticity, have low mechanical strength, low elastic modulus, and poor adsorption of lubricating oil.
2. Graphite bearings
Carbon graphite generally has good electrical conductivity, heat resistance, wear resistance, self-lubricating properties, good high-temperature stability, strong chemical corrosion resistance, higher thermal conductivity than polymers, and lower linear expansion coefficient. The friction coefficient and wear rate with chrome plated surfaces are very low under atmospheric and room temperature conditions. But it will lose its lubricity when the humidity is very low. Applying wear-resistant coatings can improve the wear resistance of carbon graphite.
Graphite can not only be used as a solid lubricant, but also added to materials such as resins, metals, ceramics, etc. to increase their anti friction properties. It can also be directly used as a friction pair material, such as in the production of bearings, high-temperature sliding bearings, sealing rings, piston rings, scraper blades, etc. in oil sensitive areas such as papermaking, wood processing, textiles, and food. The "class" symbol for carbon graphite materials used in mechanical engineering is M, and there are four series: carbon graphite materials, electrochemical graphite materials, resin carbon composite materials, and metal graphite materials.
3. Electromagnetic bearings
Electromagnetic bearings, due to the lack of direct contact between the shaft and the bearing, do not require lubrication and can operate in vacuum and over a wide temperature range. They have low frictional resistance and are not limited by speed (some can reach speeds of up to 23 million revolutions per minute, with linear speeds up to three times the speed of sound). They have a long service life and can be structurally diversified. Electrostatic bearings require a large electric field strength, which limits their application and can only be used in a few instruments. Magnetic bearings have high load-bearing capacity and stiffness, and have been used in angular momentum flywheels, flow meters, density meters, power meters, vacuum pumps, precision flow stabilizers, and gyroscopes for ultra high speed trains, ultra high speed centrifuges, hydro generators, spacecraft, etc. With the development of magnetic materials and electronic technology, the application of electromagnetic bearings is increasingly expanding.
4. Liquid dynamic pressure bearings
Single oil wedge bearings have a small eccentricity at high speeds and light loads, making them prone to instability and oil (gas) film oscillation. Oil film oscillation can cause major accidents such as equipment damage. Therefore, single oil wedge bearings are often used in mechanical equipment with medium to high speeds or high-speed heavy loads, such as rolling mills and general machine tools.
A bearing with two or more oil wedges around the journal of a multi oil wedge liquid dynamic pressure radial bearing. Before the multi oil wedge radial bearing bears the load, that is, when the center of the journal coincides with the geometric center of the bearing, there is eccentricity relative to the curvature centers of each section of the bearing surface, but the eccentricity values are equal. The pressure generated in the oil film of each bearing surface is the same, and the force on the journal is balanced.
After bearing the load, some of these eccentricity values increase or decrease, and the oil film pressure on each tile surface decreases or increases accordingly. The bearing capacity is the vector sum of these oil film pressures. Multi oil wedge bearings have lower load-bearing capacity than single oil wedge bearings, but there is additional oil film pressure on the opposite side of the main bearing surface, which can improve the stability of bearing operation. Therefore, multi oil wedge radial bearings are commonly used in high-speed and light-duty equipment, such as steam turbines, wind turbines, and precision grinders. There are many types of multi oil wedge radial bearings, and new structures with higher vibration damping capabilities are constantly emerging.
Liquid dynamic pressure thrust bearing is a thrust bearing composed of several oil wedges, with a bearing capacity of the sum of the oil film pressures of each oil wedge. It is commonly used in equipment with medium to high speeds such as water turbines, steam turbines, and compressors
5. Tilting pad bearings
It has a lower load-bearing capacity than single oil wedge liquid dynamic radial bearings, but has high rotational accuracy and good stability. It is widely used in high-speed and light load machinery, such as steam turbines and grinders. The number of tiles is generally 3-6. There are two ways to arrange tiles: when the load is directly facing between adjacent tile support points and when the load is directly facing a tile support point. If the load is the same, the eccentricity of the latter axis is smaller; If the tile surface Z that bears a larger load Z has the same oil film thickness, the former has higher load-bearing capacity, lower power consumption, and lower temperature rise.
6. Gemstone bearings
Jewel bearing is a sliding bearing made of hard materials such as gemstones. Gemstone bearings are mainly used in instruments and meters. Instrument bearings bear very small loads, but require high rotational accuracy, good sensitivity, and long service life. Gemstones have low friction, high hardness, corrosion resistance, low coefficient of thermal expansion, and high compressive strength, which can meet the requirements of instrument bearings. The materials used to make gemstone shafts include corundum, agate, microcrystalline glass, etc. Corundum is the body of alumina, which comes in both natural and synthetic forms. Natural corundum has many impurities and uneven texture, so artificial corundum is widely used.
7. Gas bearings
① Extremely low friction resistance
② Wide applicable speed range
③ Wide applicable temperature range
④ Low carrying capacity
⑤ High precision requirements for processing
Gas bearings can be used in textile machinery, cable machinery, instrument tools, gyroscopes, high-speed centrifugal separators, dental drills, low-temperature operating refrigerators, hydrogen expanders, and high-temperature operating gas circulators.
8. Oil containing bearings
Oil containing bearings are sleeve bearings that use sliding friction and lubricating oil as a lubricant and drag reducer. During initial use, they have low operating noise and manufacturing costs. However, these bearings suffer from severe wear and have a significantly shorter lifespan compared to ball bearings.
Over time, due to the use of oil seals (high-end oil seals are generally not suitable for computer heat sink products, which are ordinary paper oil seals), the lubricating oil will gradually evaporate, and dust will also enter the bearings, causing problems such as slower fan speed and increased noise. In severe cases, the wear of the bearings can also cause severe vibration due to fan eccentricity. If these phenomena occur, either open the oil seal and add oil, or only replace and purchase a new fan.
It has the characteristics of low cost, vibration absorption, low noise, and no need to add lubricating oil for a long working time, especially suitable for working environments that are not easy to lubricate or do not allow oil contamination. Porosity is an important parameter of oil containing bearings. Oil containing bearings working at high speeds and light loads require a high oil content and porosity; Oil containing bearings working at low speeds and high loads require high strength and low porosity. This type of bearing was invented in the early 20th century and has been widely used due to its low manufacturing cost and convenient use. It has become an indispensable basic component for the development of various industrial products such as automobiles, home appliances, audio equipment, office equipment, agricultural machinery, precision machinery, etc.
2026 May 4th Week Marginal Product Recommendation
MG-1A Aluminum matrix composite bearings：
MG-1A is a composite material of PTFE compound tape on aluminum shell, the PTFE is tape up to 0.20 mm thickness, enabling the bearing can be sized after being fixed, meanwhile the thick PTFE layer isolates noise. The bearing is widely applied in OA machinery, shock absorber for light design bicycle.
