The maximum required axial force refers to the greatest axial force that a screw drive must generate during operation in order to reliably achieve a defined movement or load. It takes all relevant resistances into account and is therefore a key design parameter for the drive and the overall mechanical system design.
Factors
The maximum required axial force is generally composed of several components:
- Payload / Working Load: the force required to move the actual load.
- Frictional forces in a threaded drive: dependent on thread type, lubrication, preload, and pitch.
- Additional resistance: for example, due to guides, seals, misalignment, or other mechanical factors.
- Dynamic effects: Accelerations, decelerations, or shock loads temporarily increase the required force.
- Preload: For preloaded ball screws, the preload force must also be taken into account.
Implications for Design
The maximum required axial force is critical for:
- the sizing of the drive motor,
- the selection of the lead screw, nut, and bearings,
- the safety calculation,
- the estimation of friction torque and efficiency,
- the assessment of system dynamics.
A drive system must be able to safely generate this force to ensure that the motion is performed reliably, precisely, and safely.
Practical Example
A CNC axis is designed to move a load of 500 N. Taking into account friction in the ball screw, preload, and guide resistance, the maximum required axial force is 650 N. This value forms the basis for selecting the appropriate servomotor and for sizing the spindle and bearings.