The required axial force refers to the force that must be applied along the screw axes of a screw drive to ensure a desired movement or function. It is the sum of all forces that must be overcome during operation and is a central parameter for the design of ball screws and trapezoidal screws.
What determines the required force?
The axial force typically consists of several influencing factors:
- Payload/Workload: The force that actually needs to be moved or held (e.g., the weight of a load).
- Friction in the screw drive: Depending on lubrication, screw type (ball screw or trapezoidal), pitch, and preload.
- Additional resistance: Guiding forces, seal friction, inclinations, or mechanical tension.
- Dynamic forces: Acceleration and deceleration increase the required force (mass inertia).
- Preload forces: In the case of preloaded ball screws, the preload must also be overcome.
Significance in Engineering
The required axial force is important for:
- Dimensioning of the screw and nut (load rating, rigidity, service life)
- Selection of the drive motor (torque, power)
- Assessment of safety against overload – design of the end bearings
- Calculation of efficiency
Without a concrete determination of this force, under-dimensioning, increased heating, or premature wear may occur.