The duty cycle of a ball screw describes the proportion of time during which the spindle is operated under load relative to a defined operating cycle. It is usually specified as a percentage (%) and is an important parameter for the thermal load, lubrication, and service life of the system.
Significance for ball screws
- Thermal stress: During operation, the nut generates friction and heat, which is distributed over the duty cycle. Excessive or continuous loading can impair lubrication and reduce service life.
- Service life: Ball screws are designed for specific load and speed profiles. The duty cycle influences the dynamic load rating and the wear of the balls and raceways.
- Drive design: The motor, bearings, and sealing systems must be matched to the maximum permissible duty cycle to avoid overheating or premature wear.
Typical values
- Ball screws in CNC machines or precision applications: continuous operation with a high duty cycle is usually possible due to low friction.
- Ball screws in load-change or lifting applications: the duty cycle can be intermittent, e.g., 50–70%, to avoid thermal overload.
Einflussfaktoren
- Load profile: High axial forces increase heat generation.
- Speed: Higher feed rate → more friction → lower permissible duty cycle
- Lubrication and cooling: Optimal lubrication enables a higher duty cycle.
- Environment: Temperature, dust, and cooling influence the maximum duty cycle.