Failure Mode – Insufficient Lubrication
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.
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.
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.