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(800) 603-4960

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FAILURE MODES

Excessively Tight Fits

 

Description/Cause# 1

  • Brinelling. This is caused by excessive loading on the bearing. In this particular case there were brinell marks arrayed equally spaced 360 degrees around the inner ring.

Description/Cause# 2

  • Wide ball path. This is typically caused by excessive interference fits. In this outer ring rotating application the outer ring had a similar but slightly narrower ball path.

Solution

  • Modify dimensions and tolerances on housing/shaft to allow slight play in the bearing even after the bearing is installed. Also, ensure that the housing/shaft are manufactured to the specified tolerances. (See Mounting and Fitting guide in the Technical Information section for suggested tolerances.)









Insufficient Lubrication

Description/Cause

  • Bearings appear very dry and a discolored brownish coating inside the bearing. This application was oscillating and powered with a low torque motor so the contamination visible above was enough drag to stop the motion. The bearings were oil lubricated.

Solution

  • The bearings had oil lubrication and although oil may work in lower duty applications or where there is an external lubrication system (i.e. oil bath), the solution for this situation was switching to a grease lubrication for lube-for-life. The re-tested with grease and increased life by 10x.

Lubrication Considerations:

  • Grease – It is important to ensure that the grease selected is compatible with the application. A few criteria to consider are:
  • Outgassing: This is something that may be critical for neighboring components which may become obstructed/contaminated by outgassing fumes (i.e. mirrors or lenses) or semiconductor applications.
  • Chemical/Material Compatibility: Check base oil and thickeners are compatible with mating components. Having certain plastics with incompatible chemicals in lubrications may result in premature/catastrophic failure of the assembly/device.
  • Application Temperature: Most bearing temperature ranges are -50F to +250 F. Standard oil and greases will most likely fall in this range as well. There are special lubricants that are capable of operating at 400 F, 500F, and even higher.





Improper INSTALLATION

Description/Cause

  •  Brinelling. This is caused by excessive loading on the bearing. In this particular case there were brinell marks arrayed equally spaced 360 degrees around the inner ring and outer ring equally spaced apart. The dents were located on the should (high end) of the raceway indicating that they were caused during a high axial load during installation.

Solution

  • Modify assembly tooling such that only the inner or outer ring is contacted during assembly. Only the ring that is being pressed onto the shaft/housing should be contacted. 

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