Lifetime
Lifetime
The lifetime (nominal life) is expressed by the number of circuits that 90% of a sufficiently large number of ballscrews achieve or exceed before the first signs of material fatigue occur. This figure is expressed in circuits or hours.
Nominal life formula
L = ( C / Fm )3 × 106
- L: lifetime (circuits)
- C: dynamic rating
- Fm: average axial load (N)
Calculating the average axial load
The average axial load is calculated as follows:
Fm = ∛( F13·L1 + F23·L2 + F33·L3 + … ) ÷ ∛( L1 + L2 + L3 + … )
- F: axial load (N)
- L: payload travel for the corresponding load segment (mm)
Lubrication
Lubrication
Basically, the same lubricants can be used for lubricating ballscrews as are used for ball bearings. As a rule, a single lifelong lubrication is not sufficient for the ballscrew, as, despite the use of appropriate wipers, the ballscrew spindle continually removes grease. An appropriate maintenance interval should be observed, if possible.
Key factors in selecting a lubricant
Several factors determine the selection of a lubricant. The most important ones are:
| Spindle speed | Spindle speed |
|---|---|
| Operating temperature | Operating temperature |
| Ballscrew load | Ballscrew load |
Assembly specifications
Assembly specifications
Radial or eccentric forces should not act on the nut system during assembly. Parallel and right-angle deviations must not exceed 0.02 mm.
Wiper
Wiper
Various types of wipers, made of felt or plastic, for example, are available for protecting ballscrews from dirt and contamination.
Operating temperature
Operating temperature
The permissible operating temperature of ballscrews is in the range of -20°C to +80°C.