The unsupported spindle length refers to the distance of a spindle between two bearings or mounting points that is freely spanning without lateral support or a bearing surface. It is a key parameter for the stiffness, stability, and buckling susceptibility of a lead screw.
The unsupported spindle length affects:
- Bending due to deflection of the spindle under axial or radial load
- Buckling resistance: Longer unsupported sections increase the risk of buckling
- Positioning accuracy: Elastic deformation leads to travel deviations
- Drive torque: Greater deflection can increase friction losses
Influencing factors
- Spindle diameter: larger diameters increase stiffness
- Material and modulus of elasticity: harder materials resist bending better
- Support of the spindle ends
- Axial and radial forces act on the unsupported length
Practical relevance
- An important parameter for vertical axes, long-stroke spindles, and lightweight applications
- Reducing the unsupported length by means of intermediate bearings increases stiffness and service life
- Basis for dimensioning the spindle diameter and bearing arrangement