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Analysis Of Noise Generated By FAG Bearings

Source:  skf bearing  Time:  2020-11-24

The free vibration of the cage during the rotation of the FAG bearing and its collision with rolling elements or ferrules will cause this noise. It may appear in all kinds of bearings, but its sound pressure level is not too high and low frequency. Its characteristics are:

 

a. Both stamping cage and plastic cage can be produced.

 

b. Either thin oil or grease lubrication will appear.

 

c. It is most likely to occur when the outer ring is subjected to bending moment.

 

d. It is easy to appear when the radial clearance is large.

 

Since the cage pocket gap and cage and ring gap are unavoidable in the bearing product, it is very difficult to completely eliminate the cage noise, but it can be improved by reducing the assembly error and optimizing the reasonable clearance and cage movement.

 

Another kind of special noise of the cage is the noise caused by the self-excited vibration of the cage caused by the friction between the cage and the guide surface of other bearing parts. The stamped cage of deep groove ball bearing is thin, the bending stiffness in the radial and axial plane is low, and the overall stability is poor. When FAG bearing rotates at high speed, it will produce self-excited vibration due to bending deformation, causing "buzzing sound".

 

When the FAG bearing is under radial load and the grease performance is poor, the noise of "click, click" will be heard at the beginning of operation. This is mainly due to the sudden acceleration of the rolling elements after they leave the load zone and the cage The noise caused by the collision is inevitable but will disappear after a period of operation.

 

Measures to prevent cage noise are as follows:

 

a. In order to stabilize the revolution movement of the cage, the ferrule guide method should be adopted as much as possible and the guide surface should be fully lubricated. The structure of the tapered roller bearing under high-speed working conditions should be improved, and the roller-guided L-shaped cage should be changed. Z-type cage guided by the ring rib.

 

b. When the FAG bearing rotates at high speed, the vibration amplitude of the cage of a bearing with a large pocket gap is much larger than that of a cage with a small pocket gap, so the value of the pocket gap is particularly important.

 

c. Pay attention to minimize the radial clearance.

 

d. Try to improve the manufacturing accuracy of the cage and improve the surface quality of the cage, which is beneficial to reduce the noise caused by the collision or friction between the rolling elements and the cage.

 

e. Actively adopt advanced cleaning technology to effectively and thoroughly clean the spare parts and the products after fitting to improve the cleanliness of the bearing.

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Raceway noise is a kind of smooth and continuous noise caused by rolling elements rolling in the raceway when FAG bearings rotate. It only attracts people's attention when its sound pressure level or tone is extremely large. In fact, the sound energy excited by the raceway sound is limited. For example, under normal conditions, the high-quality 6203 bearing raceway sound is 25 ~ 27dB. This kind of noise is most typical of single row deep groove ball bearings that bear radial load. It has the following characteristics:

 

a. Noise and vibration are random;

 

b. The vibration frequency is above 1kHz;

 

c. No matter how the rotation speed changes, the main noise frequency is almost unchanged while the sound pressure level increases with the rotation speed;

 

d. When the radial clearance increases, the sound pressure level increases sharply;

 

e. As the rigidity of the bearing seat increases, the lower the total sound pressure level, even if the speed increases, the total sound pressure level will not increase much;

 

f. The higher the lubricant viscosity, the lower the sound pressure level, but for grease lubrication, its viscosity and the shape of soap fibers can affect the noise value.

 

The sound source of the raceway is caused by the natural vibration of the ring after being loaded. Because of the elastic contact between the ring and the rolling element, a nonlinear vibration system is formed. When the lubrication or machining accuracy is not high, the natural vibration related to this elastic characteristic will be excited, and it will become noise when transmitted to the air. As we all know, even if the most advanced manufacturing technology is used to process bearing parts, there will always be small geometric errors of varying degrees on the working surface, so that small fluctuations between the raceway and the rolling elements will excite the natural vibration of the vibration system.

 

Although the raceway noise of FAG bearings is inevitable, high-precision machining of the working surface of the parts can be adopted, the correct selection of bearings and the precise use of bearings can reduce noise and vibration.

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