Dynamic Load Rating
The dynamic load rating C is the load at which a guide or bearing series reaches a defined nominal service life (typically 100 km travel). It is the key parameter for L10 service life calculation: the higher C, the longer the service life at a given operating load.
Definition
The dynamic load rating C is a standardized characteristic value (per ISO 14728 for linear guides, ISO 281 for rolling bearings). It states the constant load at which 90 % of a statistical product series show no material fatigue after a defined reference travel distance (e.g. 100 km) — the L10 criterion. The load rating is given by the manufacturer in the catalog and depends on the number, size, and arrangement of the rolling elements. Roller guides achieve higher C values than ball guides of the same installation size due to line contact.
Application in System Design
When selecting a guide, the equivalent dynamic load P (resulting from force and moment effects) is compared with the load rating C. The nominal service life L is calculated as L = (C/P)^p, where the exponent p = 10/3 for rollers and p = 3 for balls. A higher load rating C allows either a longer service life at the same load P, or a smaller, lighter carriage for the same service life requirement.
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