The limit load describes the maximum load that a mechanical component—such as a ball screw drive, a trapezoidal lead screw, or a bearing—can withstand without suffering permanent deformation, material damage, or loss of function. It is a safety-relevant characteristic value and defines the upper limit of permissible loading for a system.
In technical design, a distinction is made between different types of limit load:
Static limit load (static load rating C₀): Maximum load at which no permanent deformation occurs on rolling elements or raceways.
Dynamic limit load (dynamic load rating C): Load under which the component achieves a defined service life under repeated loading (e.g., 10⁶ revolutions).
Thermal load limit: the load limit beyond which heat generated by friction causes damage.
Buckling load: The maximum compressive force at which slender shafts lose their stability (Euler buckling).
For ball screw drives, the static and dynamic axial load ratings in particular are the decisive limit values. They are specified by the manufacturer in accordance with DIN 69051 (or DIN ISO 3408).
Example
A ball screw drive with a static load rating of 12 kN must not be subjected to axial forces above this value. If this limit is exceeded, plastic deformation occurs at the contact points between the balls and the raceways (pitting), which leads to premature failure of the drive.