Shaft Loading and Sealing vs. Bearing Life Expectancy

The mechanical life of an encoder is mainly determined
by the life of the unit's bearings. Several factors
affect bearing life, including shaft loading, heat,
ingress and rotational speed.
Shaft loading is likely the
top cause of premature
bearing failure. There are
two types of loading to
consider - radial and axial.
Radial loading is the perpendicular
force applied
to the shaft. Common
causes of radial loading include misalignment of the
shaft when mounted or use of items such as pulley
and gears. Axial loading is the parallel force, or force
applied along the same direction of the shaft. As radial
and/or axial loading increases, bearing life shortens.
For this reason, the minimum amount of shaft
loading or misalignment should always be the goal
when installing an encoder. One important loading
fact to remember: radial shaft loading increases as a
linear function the further away from the bearing the
force is applied, much the same way a longer wrench
gives you greater leverage against a stubborn bolt.
It is always best practice to place any unavoidable
radial load as close to the bearings as possible.