Thomson Linear Motion Optmized
Profile Rail Bearings & Guides - Preloading
Design and Theory
Preloading a profile rail linear bearing is accomplished by installing slightly larger bearings into the carriage. This produces an internal force between the carriage and rail, which is called preload.
Preload will eliminate internal clearances between the rail and carriage, resulting in zero backlash. Preload will minimize elastic deformation caused by external forces. Less deformation results in increased rigidity.
Preload specification
Profile rail bearing preload is generally expressed as a function of the dynamic load. A bearing could be described as having a preload of "0.08 C" with the "C" being the dynamic load of the carriage.
The following is an example of how to calculate the preload of a carriage.
A preloaded bearing loaded beyond the preload value has the same characteristics as a clearance bearing. In the example above, if the applied load is greater than 1.7kN then the preload has no benefit.The carriage has dynamic load capacity of 21.1kN,The Preloaded is specified as 0.08 C or 0.08 x 21.1kN = 1.7kN
Preload = 1.7kN
Suggested Preloads
The following chart provides some general guidance for when a particular preload may be chosen.
Table of suggested preloads
