9 main factors you must consider when selecting bearings
Sep 23, 2022
Different types of bearings have different features or properties for different designs. Due to the variability and complexity of the application as well as the specific installation position of the bearing, there is no fixed mode for the selection of bearing type. When selecting the bearing type to meet the specific requirement of a certain equipment, it is recommended to consider the following 9 main factors.
In mechanical design, the size of the shaft is generally determined first, and then the bearing is selected according to the size of the shaft. Usually, ball bearings are used for small shafts; cylindrical roller bearings, spherical roller bearings, and tapered roller bearings (sometimes ball bearings are also optional) for large shafts. If the radial space of the bearing installation part is limited, bearings with smaller radial section height should be used. Such as needle roller bearings, some series of deep groove ball bearings, angular contact ball bearings, cylindrical or spherical roller bearings and thin section ball bearings. If the axial space of the bearing installation part is limited, bearings with a smaller width shall be adopted then.
Actual load is usually the determining factor in the selection of bearing size. Roller bearings have a higher capacity than ball bearings with the same external dimensions. Usually ball bearings are suitable for light or medium loads, and roller bearings are suitable for heavy loads.
Only bear radial load can choose deep groove ball bearing and cylindrical roller bearing. Only bear axial load can choose thrust ball bearing and thrust cylindrical roller bearing . When there is radial load and axial load (combined load), angular contact ball bearings or tapered roller bearings are generally selected. If the radial load is large and the axial load is small, deep groove ball bearings and cylindrical roller bearings with ribs on the inner and outer rings can be selected. If there is also large deformation of the shaft or housing and poor installation alignment, spherical ball bearings and spherical roller bearings can be selected. If the axial load is large and the radial load is small, the thrust angular contact ball bearing can be selected. If the four point contact ball bearing also requires self-aligning performance, the thrust spherical roller bearing can be selected.
The working speed of the rolling bearing mainly depends on its allowable operating temperature. Bearings with low frictional resistance and less internal heat generation are suitable for high-speed operation. When only bearing radial load, deep groove ball bearings and cylindrical roller bearings can reach higher speed. If bearing combined load, angular contact ball bearings should be selected. High speed can be achieved by specially designed high precision angular contact ball bearings. The rotational speed of various thrust bearings is lower than that of radial bearings.
For most machinery, the selection of bearings with grade 0 tolerance is sufficient to meet the equipment requirements. But when there are strict requirements on the rotation accuracy of the shaft, such as machine tool spindles, precision machinery and instruments. Deep groove ball bearings with higher tolerance, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings and thrust angular contact ball bearings should be selected.
The rigidity of a rolling bearing is determined by the amount of elastic deformation that occurs when it bears the load. In general, this deformation is small and can be ignored, but in some machines, such as machine tool spindle systems, the static rigidity and dynamic rigidity of the bearing has a great influence on the characteristics of the system. In general, roller bearings have higher rigidity than ball bearings. Various types of bearings can also improve the rigidity by properly "pre-loading".
6.Noise and Vibration
The noise and vibration of the bearing itself are generally very low. However, for small and medium motors, office machinery, household appliances and instruments that have special requirements for noise and running stability, low-noise bearings are more commonly selected.
The most common configuration of bearings is to install a set of axially positioned "fixed bearings" at one end of the shaft and a set of axially movable "floating bearings" at the other end to prevent the stuck phenomenon due to thermal expansion and contraction of the shaft. “Floating bearing" is a cylindrical roller bearing with no ribs on the inner ring or outer ring, which are commonly applied. At this time, overfilling fit can be taken between the inner ring and the shaft or between the outer ring and the housing hole. Sometimes non-separable deep groove ball bearings or spherical roller bearings can also be used as floating bearings. However, during installation, the inner ring and the shaft or the outer ring and the housing hole should choose a clearance fit to ensure that the inner ring or the outer ring has a sufficient freedom of axial movement.
The frictional resistance of the ball bearing is smaller than that of the roller bearing. When only under radial load, the frictional resistance of the radial contact bearing is small. When only under axial load, the frictional resistance of the axial contact bearing is small. When under combined load, Angular contact bearings with angles close to the load angle have the least frictional resistance. In instruments and machinery that require low friction torque, ball bearings or cylindrical roller bearings are more suitable. In addition, contact seals should be avoided for low-friction torque bearings. At the same time, it is recommended to use drop lubrication, oil-gas lubrication or other lubrication methods which are good for wear reduction.
9.Find a factory with an strong technical department or team
CHG factory (was called as LYHG) has an professional technical team, has won over 200 patents and several rewards as well, it can give in-time service including product selection, draft drawings, 3D drawings, 3D design display videos, technical data sheets required, and service during installation and after sales.
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