Planetary Roller Screws

Planetary roller screws convert rotary motion into linear motion. The drive unit is a roller between the screw and the nut, the main difference with ball screws is that the load transfer unit uses a threaded roller instead of a ball. Planetary roller screws have multiple contact points and can withstand large loads with very high resolution.

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Roller Screw VS Ball Screw

Planetary roller screws are able to withstand higher static and dynamic loads due to the high number of contact points, with static loads up to 3 times that of ball screws and a life expectancy up to 15 times that of ball screws.

The large number of contact points and the geometry of the contact points make planetary screws more rigid and shock resistant than ball screws, while also providing higher speeds and greater acceleration.

Planetary roller screws are threaded, with a wider range of pitches, and planetary roller screws can be designed with smaller leads than ball screws.

Classification And Application Of Planetary Roller Screws

Standard type planetary roller screws are a high precision, high load design that provides very stable drive torque. Screws are mostly used in high load, high speed and high acceleration applications. Special gears on the rollers and nuts allow the screws to maintain good motion even under the harshest conditions.

Recirculating planetary roller screws are a cyclic roller design in which the rollers are guided in a carrier whose movement is controlled by a set of cams.This design combines very high positioning accuracy resolution and stiffness and at the same time guarantees very high loading forces.This design is suitable for high precision, low to medium speed operation.

Standard Planetary Roller Screws

Recirculating Planetary Roller Screws

Reverse planetary roller screws, where the rollers do not move axially along the screw, but their travelling motion is in the internal threads of the nut. This design achieves a higher minus rating through smaller lead distance, which reduces drive torque. The more compact dimensions make direct guidance possible. Gears are designed between the roller and the screw to provide a smoother and more stable synchronised rotary motion.

Reverse Planetary Roller Screws

Differential Planetary Roller Screws

Differential planetary roller screws are characterised by their differential motion, which allows them to have a smaller lead than general planetary roller screws. When applied to electromechanical actuators, they can obtain a larger reduction ratio while other conditions remain unchanged, and their compact structure allows electromechanical actuators to have a higher power-to-volume ratio and power-to-mass ratio, which is more suitable for high-speed and heavy-duty applications.

Application Scenarios

Mechanical Presses	Automotive Actuator	Welding Robot
Injection Moulding		Nuclear Industry
Aerospace	Steel Industry	Stamping Machines
Oil Industry
	Electric Cylinders	Precision Ground Machines
Military Equipment
	Precision Instruments
Medical Equipment

RSS/RSM Planetary Roller Screws

Planetary Roller Screws with centrally located nut flange and no axial preload.

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RS Planetary Roller Screws

Highest efficiency rolling motion (even in shallow lead designs).

Multiple contact points that carry large loads with very high resolution.

Small axial movement (even with very shallow leads).

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RS Planetary Roller Screws

High rotational speeds with faster acceleration (no adverse effects).

The most reliable screw solution available.

Higher cost option with highest performance.

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RSR Planetary Roller Screws

Maximum backlash of single nuts: 0.03mm (can be less on request).

Nuts with lubrication holes available if required.

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RSI Inverted Planetary Roller Screws

An inverted roller screw works on same principle as a planetary roller screw. In order to reduce the overall actuator dimensions, either the nut or screw can be directly used as a push tube.

An inverted roller screw has a high speed capability similar to a planetary roller screw, but the load acts directly on the translating push tube.

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