How to use FAG bearings to improve shaft support rigidity

The FAG bearing pre-tightening method can be used to improve the bearing rigidity. The ball bearing or the tapered roller bearing can adopt the axial pre-tightening method, and the short cylindrical roller bearing can adopt the radial pre-tightening method, which can significantly improve the rigidity of the shaft bearing. At the same time, the bearing clearance is eliminated or a small negative clearance is obtained. However, under the condition that the rotation speed is not too high and the temperature rise is not large, it is better to adjust to a small negative clearance state. When preloading is applied, the deformation should be continuously measured. Note that in the low value stage of deformation, the deformation is nonlinear with the increase of the preloading load; in the high value stage, the deformation is linear with the increase of the load.

Once the deformation-load has a linear relationship, the pre-tensioning load is stopped immediately, and a constant stiffness is obtained. Thereafter, there is a fixed relationship between the axial stiffness and the radial stiffness of the bearing, independent of the applied load.

The above-mentioned deformation amount can be measured by, for example, abutting the dial gauge against an appropriate end portion of the bearing end face or the shaft, and observing the change of the reading with the preload load. The pre-tightening method has its disadvantages, such as increasing the friction torque of the FAG bearing, increasing the temperature rise, shortening the life, etc., so it is necessary to comprehensively consider the trade-offs and gain the appropriate pre-tightening amount.

The configuration of the bearing arrangement of the bearing has a great influence on the bearing rigidity. Generally speaking, for the ball thrust bearing and the roller bearing of the centripetal thrust type, it is preferable to adopt the large end face of the outer ring when paired (ie, the pressure line is formed). The configuration of the pressure cone tip outwards is such that the FAG bearing has a large ability to resist the overturning moment, and the amount of preload that is adjusted when the temperature changes is less changed.

Multi-bearing support is adopted. Under the condition that the axial position allows, two or more bearings are used as radial support for each fulcrum, which can improve the support rigidity. For example, in the recent spindle parts of machine tools, a plurality of sets of radial thrust bearings mounted axially preloaded as shaft supports of the same fulcrum are widely used.

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