Ball Screw Life Calculator

| Added in Construction

Understanding Ball Screw Life

A ball screw is a mechanical device that converts rotational motion into linear motion with high efficiency and precision. The service life of a ball screw assembly depends on several factors including the load it carries, operating speed, and environmental conditions.

Formula

[\text{Ball Screw Life} = \frac{10^6}{60 \times \text{RPM}} \times \left(\frac{C}{P \times f}\right)^3]

Where:

  • BSL = Ball Screw Life (hours)
  • RPM = Average rotational speed (revolutions per minute)
  • C = Basic static load rating (daN)
  • P = Average axial load (daN)
  • f = Service factor (dimensionless)

Example Calculation

For a ball screw operating at 75 RPM with a basic static load rating of 150 daN, carrying an average axial load of 80 daN, and using a service factor of 1.25:

  1. Calculate the time factor: 10^6 / (60 × 75) = 10^6 / 4500 = 222.22
  2. Calculate the load ratio: 150 / (80 × 1.25) = 150 / 100 = 1.5
  3. Cube the load ratio: 1.5³ = 3.375
  4. Multiply the factors: 222.22 × 3.375 = 750 hours

The expected ball screw life is approximately 750 hours of operation.

Frequently Asked Questions

Ball screw life is the expected operating duration in hours before the ball screw assembly requires maintenance or replacement, calculated based on load conditions and operating speed.

The calculation uses the formula: BSL = (10^6 / (60 × RPM)) × (C / (P × f))³, where C is the basic static load rating, P is the average axial load, RPM is the rotational speed, and f is the service factor.

The service factor (f) accounts for operating conditions such as shock loads, vibration, and environmental factors. Typical values range from 1.2 to 1.25 for standard applications, with higher values for more severe conditions.

Use daN (decanewtons) for both the basic static load rating and average axial load. RPM should be the average rotational speed, and the service factor is dimensionless.