Angle contact ball bearing failure judgment
In the manufacturing industry, the most commonly used spindles are high-speed precision angular contact ball bearings that rotate at very high speeds, sometimes producing high heat. If this phenomenon is not eliminated in time, it will cause the angular contact ball bearing to overheat, and the temperature of the corresponding part of the machine tool will increase and cause thermal deformation. In severe cases, the spindle and the tailstock will not be equal, which not only affects the accuracy and machining accuracy of the machine tool itself. And will burn the bearing.
Rated fatigue life refers to the operation of a group of bearings of the same type under the same conditions, in which 90% of the angular contact ball bearings do not have the total number of revolutions caused by rolling fatigue. When the speed is constant, the total running time is used to indicate the rated fatigue life. When studying the life of a thrust ball bearing, it is not only possible to consider the fatigue life, but also to consider the performance of the bearing and combine several use limits. For example, the grease life of grease lubricated bearings. Since the noise life, the wear life, and the like vary depending on the application, the use limit is different, and therefore, the experience limit is often selected in advance. Therefore, it is difficult to know the true cause of the damage by investigating only the angular contact ball bearing damage. However, if you know the use of the thrust ball bearing machinery, the conditions of use, the structure around the bearing, and understand the situation before and after the accident, combined with the damage state of the bearing and several reasons, it can prevent similar accidents from happening again.
The judgment of whether the angular contact ball bearing is available is mainly determined by considering the degree of bearing damage, mechanical properties, importance, operating conditions, and the period of the next maintenance. If you have the following defects, you can no longer use them. You must replace the new thrust ball bearings. There is a crack or a gap in any of the inner ring, the outer ring, the rolling element, and the cage. Wear failure is one of the common failure modes of various types of bearings. It is usually classified into the most common abrasive wear and adhesive wear according to the form of wear. We can use the following techniques to determine if the bearing has reached wear failure:
1. Oil film resistance diagnosis technology
Features: The same criteria can be used for different working conditions. It has a poor diagnostic effect on abnormalities such as surface peeling, indentation, and cracks.
Application range: Suitable for occasions where the rotating shaft is exposed.
2. Vibration diagnosis technology
Features: Vibration diagnostic technology is widely used; online monitoring can be realized; diagnosis is fast, and diagnostic theory is mature.
Scope of application: Particularly suitable for fault monitoring of angular contact ball bearings in rotating machinery.
3. Ferrography diagnostic technology
Features: The machine does not need to be disintegrated; the investment is low, the effect is good; the early fatigue failure of the oil-free bearing can be found; the wear mechanism can be studied.
Scope of application: It is suitable for fault diagnosis of angular contact ball bearings lubricated with lubricating oil, which is difficult for bearings lubricated with grease.
4. Temperature diagnostic technology
Features: Simple diagnosis; better judgment on bearing burns.
Applications: Simple routine diagnostics for bearings in machines.
5. Optical fiber monitoring and diagnosis technology
Features: The fiber displacement sensor has high sensitivity; the signal is directly extracted from the oil-free bearing surface, and the signal-to-noise ratio is improved; the manufacturing quality, surface wear degree, load, lubrication and gap of the angular contact ball bearing can be directly reflected.
Applications: Suitable for machines where the sensor can be mounted in a housing.
6. Acoustic emission diagnostic technology
Features: Quick and easy diagnosis; online monitoring.
Scope of application: New technologies developed in recent years have been used less in bearing condition monitoring.
When taking the oil-free bearing directly by hand during the test, fully wash the sweat from the hand and apply it with high-quality mineral oil before handling. In the rainy season and summer, pay special attention to rust prevention. Under certain special operating conditions, angular contact ball bearings can achieve longer life than traditional calculations, especially at light loads. These special operating conditions are when the rolling surfaces (tracks and rolling elements) are effectively separated by a lubricant film and the surface damage caused by contaminants is limited. In fact, under ideal conditions, so-called permanent bearing life is possible.
When the angular contact ball bearing rotates, the raceway surface of the inner ring and the outer ring is in rolling contact with the rolling element, the running track is a dark surface, and the running track attached to the raceway surface is not abnormal, thereby being known Load conditions, so when removing oil-free bearings, please pay close attention to and observe the running track of the raceway surface.
Reprinted from the network