Roller screw vs ball screw
Both convert rotary motion to linear motion. The difference is in the contact geometry — and that difference decides load, life and precision.
A ball screw carries load through recirculating balls that make point contact with the raceways. A planetary roller screw replaces those balls with threaded rollers that make line contact across many turns. The result is far more contact area in the same envelope.
| Criterion | Planetary roller screw | Ball screw |
|---|---|---|
| Load capacity | Higher — line contact across many rollers | Lower — point contact at recirculating balls |
| Service life | Longer under high load and high duty cycle | Shorter under equivalent heavy load |
| Achievable lead | Very fine leads possible | Limited by ball diameter |
| Stiffness | High — many simultaneous contacts | Moderate |
| Shock resistance | High — load shared across rollers | Risk of brinelling under shock |
| Max speed at fine lead | High | Limited by recirculation |
| Initial cost | Higher | Lower |
| Best fit | Heavy load, high cycles, precision, long life | Cost-sensitive, moderate load |
When to choose a roller screw
- Continuous, high duty-cycle operation where downtime is costly.
- Heavy thrust in a limited diameter.
- Fine leads a ball screw cannot be manufactured to.
- Shock and vibration that would damage ball raceways.
- Applications needing long, predictable service life.
When a ball screw may suffice
For light-to-moderate loads, lower cycle counts and cost-sensitive designs, a ball screw can be the economical choice. Our engineers can help you make the call for your duty profile.