How to install precision bearings

2022-08-14
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How to install precision bearings

installation method of precision bearing:

1. Requirements for matching parts of precision bearing:

1) because the precision of precision bearing itself is 1 μ M, so it is required that the matching parts (shaft, bearing seat, end cover, retaining ring, etc.) have high dimensional accuracy and shape accuracy, especially the accuracy of the mating surface should be controlled at the same level as the bearing, which is very important and is most likely to be ignored

2) it must also be noted that if the matching parts of the precision bearing fail to meet the above requirements, the error of the precision bearing after installation is often several times larger than that of the original bearing, or even more than 10 times. It is not a precision bearing at all, because the error of the matching parts is often not simply superimposed on the error of the bearing, but amplified by different multiples

2. Matching of precision bearings:

in order to ensure that the bearings do not produce excessive deformation after installation, we must do:

(1) the roundness of the shaft and the seat hole and the verticality of the shoulder should be in accordance with the corresponding accuracy of the bearings

(2) it is necessary to accurately calculate the interference amount of the rotating ferrule and the appropriate amount of the fixed ferrule

the burning interference of the rotating ferrule should also be small within the possible range. As long as the influence of thermal expansion under the working temperature and the influence of centrifugal force under the maximum speed are ensured, the creep or sliding of the tight fitting surface will not be caused. According to the working load and bearing size, the fixed ferrule selects a very small clearance fit or interference fit. Too loose or too tight is not conducive to maintaining the original accurate shape

(3) if the bearing operates at high speed and the working temperature is high, special attention should be paid to the matching of the rotating ring not to be too loose to prevent eccentric vibration, and the matching of the fixed ring should not have clearance to prevent the ring from deforming and exciting vibration under load

(4) the condition of small interference fit for the fixed ring is that both sides of the matching surface have high shape accuracy and small roughness, otherwise it will be difficult to install and more difficult to disassemble. In addition, the influence of thermal elongation of the main shaft needs to be considered

(5) for the main shaft with paired double angular contact ball bearings, most of the load is light, and if the fit interference is too large, the internal axial preload will be significantly larger, which will cause adverse effects. The load of spindles with double row short cylindrical roller bearings and tapered roller bearings is relatively large, so their fitting interference is also relatively large

3. Methods to improve the actual matching, otherwise it will have a negative impact on the fitting accuracy of instrument optical parts and metal coating:

1) in order to improve the actual fitting accuracy during bearing installation, it is necessary to use the measurement methods and measuring tools that do not deform the bearing to carry out the actual precise measurement of the fitting surface size of the bearing's inner hole, which has reached 106million users in China and the outer circle, All measurement items related to inner diameter and outer diameter can be measured, and the measured data can be comprehensively analyzed, based on which, 11 The console is separated from the main machine, and the size of the bearing installation part of the shaft and seat hole is precisely matched. When actually measuring the corresponding size and geometry of the shaft and seat hole, it should be carried out under the same temperature as when measuring the bearing

2) in order to ensure a high actual matching effect, the roughness of the surface of the shaft and seat hole matching the bearing should be as small as possible

3) during the above measurement, two groups of marks that can show the direction of the maximum deviation should be made on the outer circle and inner hole of the bearing, as well as on the corresponding surface of the shaft and seat hole on both sides close to the assembly chamfer, so that the maximum deviation of the matching two sides can be aligned in the same direction during the actual assembly, so that the deviation of both sides can be partially offset after assembly

4) the purpose of making two groups of orientation marks is to comprehensively consider the compensation of deviation, which not only improves the rotation accuracy of the supports at both ends, but also partially eliminates the coaxiality error of the seat hole between the two supports and the journal at both ends. The surface strengthening measures for the mating surface, such as sand blasting and plugging the primary inner hole with a precision plug with a slightly larger diameter, are conducive to improving the mating accuracy

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