MANAGING MISALIGNMENT IN LINEAR MOTION SYSTEMS

When design engineers evaluate linear bearings, they
always ask about performance attributes such as speed,
load capacity and lifecycle. Then they want to know the
price. It's rare, however, that they ask about the bearing's
sensitivity to misalignment. And that's a big mistake,
because misalignment represents one of the leading
causes of premature linear bearing wear and failure.
Linear bearings that should last for years based on
expected life calculations can quit after a just few months
if they are not aligned to the geometric tolerances they
require to run smoothly. Usually, alignment problems begin
with the design and preparation of the machine frame
itself. It may not be fl at, straight or parallel enough for a
bearing to mounted properly. For example, mounting
surfaces may have one or more high spots that will read
through to the installed bearing rails. Or the frame design
may make it diffi cult to mount bearing rails parallel to one
another in the horizontal axis, vertical axis or both.