1. Inadequate Bearing Lubrication
When a bearing operates under oil-starved conditions, adhesive wear is likely to occur, degrading the working surface. Tears from adhesive wear can easily enter the bearing cage, subjecting it to abnormal loads. In severe cases, this may lead to cage breakage.
2. Bearing Creep
Creep refers to the sliding of the bearing ring. When there is insufficient interference on the mating surface, the load point shifts circumferentially due to sliding. This causes the ring to deviate from its relative position with respect to the axis or housing, creating uneven stress on the cage.
3. Abnormal Loads on the Bearing Cage
Improper installation (misalignment or excessive interference) reduces clearance, increasing friction and heat generation. This softens surfaces and may cause premature abnormal spalling. As spalling expands, foreign objects entering cage pocket holes can block movement and generate additional loads, eventually causing fracture through a continuous wear cycle.
4. Material Defects in the Bearing Cage
Manufacturing flaws significantly reduce cage durability. These include cracks, large non-homogeneous metal inclusions, shrinkage cavities, bubbles, and riveting issues (missing rivets, loose rivets, gaps in bonded surfaces of two-piece cages) or excessive riveting pressure.
5. Ingress of Hard Foreign Bodies
Entry of hard foreign materials or other impurities creates three critical issues: accelerated abrasive wear of cage surfaces, increased friction between components, and potential blockage of normal cage movement – all significantly reducing service life.
6. Cage Breakage Mechanisms
Cage breakage typically results from three interrelated factors: rapid cage vibration creating fatigue stress, excessive wear reducing structural integrity, and blockage by foreign objects causing sudden overload failure.
7. Cage Wear Factors
Primary causes of cage wear include inadequate lubrication (creating metal-to-metal contact) and presence of abrasive particles. Both conditions accelerate material loss from cage surfaces, eventually compromising structural integrity.
8. Blockage by Raceway Debris
Flaky materials or hard particles from deteriorating raceways often become trapped between the cage and rollers. This impedes proper roller rotation around their axes, creating excessive friction and uneven loading on cage components.
9. Bearing Vibration Effects
Excessive bearing vibration generates significant inertial forces that create cyclic stress on the cage. Over time, this leads to fatigue cracks initiation and propagation. Without intervention, these cracks will eventually cause complete cage fracture.
10. Excessive Rotational Speed
Operating beyond the cage’s designed speed limit creates dangerous centrifugal forces. These forces can exceed the material’s structural capacity, causing deformation and eventual catastrophic failure of the cage.