A roller screw works by using multiple threaded rollers as rolling elements to convert rotary motion into precise linear motion with high efficiency.
A roller screw is a type of linear actuator that operates much like a ball screw, but instead of using ball bearings circulating within threads, it utilizes multiple threaded rollers positioned between the screw shaft and the nut. This design allows for greater contact area and higher load capacity compared to ball screws.
Core Components
The system typically consists of three main parts:
- Screw Shaft: A threaded shaft, often referred to as the screw.
- Nut: A cylindrical component with internal threads that mate with the screw shaft.
- Rollers: Multiple threaded rollers arranged helically between the screw shaft and the nut.
The Mechanism in Action
The rollers spin in contact with, and serve as low-friction transmission elements between, screw and nut. As the screw or nut rotates, the rollers revolve around the screw shaft and simultaneously rotate on their own axes. This rolling contact significantly reduces friction compared to traditional lead screws, where surfaces slide against each other.
- Thread Matching: The thread of the screw is typically identical to the internal thread of the nut.
- Roller Design: The rollers typically have a single-start thread with convex flanks that limit friction at the rollers' contacts with screw and nut. This convex profile minimizes the contact stress and further enhances efficiency.
This rolling action provides smooth, precise linear movement when rotational force is applied to either the screw or the nut.
Key Advantages
Roller screws offer several advantages due to their design:
- High Load Capacity: The increased contact area provided by the rollers distributes the load effectively.
- High Stiffness: The large number of contact points provides greater rigidity.
- Long Service Life: Reduced friction leads to less wear.
- High Efficiency: Minimizing friction results in less energy loss.
- Precision: Capable of achieving very accurate positioning.
Typical Applications
Roller screws are used in applications requiring high force, speed, duty cycle, or precision.
- Aerospace (flight control surfaces)
- Industrial Automation (robotics, press machines)
- Machine Tools (actuators, feed axes)
- Medical Equipment (imaging systems, surgical robots)
