Roller Screw (Satellite) [3.55MB]

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Satellite roller screws

Satellite roller screws, an upgrade on ball screws?

"I need more performance from my existing linear device." !

"My hydraulic linear actuation system is a major part of my maintenance schedule"

"My ball screw is failing prematurely due to high duty cycle". !

"I have reached the boundary of performance from my existing ball screw but have no way of increasing its dimensions within the current design" !

Sound familiar ? These are some of the questions being asked by designer engineers or maintenance engineers when coming to ABSSAC in search of a linear technical assistance.

The satellite roller screw program, exclusively available from ABSSAC limited, is proving to be a formidable advantage in the linear technology sector. With a traditional ball screw design, the captivated ball bearings transfer the load between the screw and nut as they recirculate in the ball nut housing. To increase the load capacity of the ball screw you have to either increase the amount of ball bearings in the nut housing, for example by doubling the actual ball returns or alternatively you have to increase the amount of times the ball bearings recirculate within the ball nut housing . Of course the final option is to choose a larger, more expensive ball screw !. All these options ultimately increase the load capacity, but in every case there is still a limitation of the actual load bearing surface area per ball bearing.

This is where the satellite roller screw has large an legitimate advantage. As shown in the cut away photo; A satellite roller screw employs, matched rollers to rotate (or satellite as the product name suggests) around the screw during actuation instead of ball bearings. By its inherent design, there is an immediate increase in the physical amount of contact points on the screw that can support the load compared with that of the same diameter ball screw.

The admissible static and dynamic load capacities are therefore considerably higher than that of ball screw for the same diameter. In fact the static load can be 3 times greater than that of ball screws and their lifespan is 15 times longer.

The many points of contact also give a satellite roller screw greater rigidity and shock tolerance than a ball screw without a compromise to friction or efficiency.

Another key feature of Satellite roller screws is that they can rotate significantly faster and support much greater accelerations than ball screws as there is no recycling of the ball bearings. In fact, a roller screw mechanism can handle twice the rotation speed of a ball screw.

Taking the product to another level, it is possible to supply planetary roller screws with smaller leads compared to ball screws. As the lead is a function of the pitch of the planetary roller screw, the lead can be very small (0.5mm and even less). The lead can be chosen and supplied without any geometrical changes of both the screw shaft and the nut body. In a ball screw the lead is limited by the dimension (Outside Diameter) of the bearing ball, which is a standard feature.

The ABSSAC satellite screw product has two standard designs directly aimed at replacing less effective ball screw designs. There is also a full design capability of the standard satellite screw program which continues to "upgrade" linear designs around the world.

Applications to date have included aerospace, medical, exploration and machine tool.

As standard satellite screws can be supplied with outside diameters as small as 10mm up to 200mm. Leads can be as fine as 0.25mm. The product can be finitely accurate and capable of being adapted into very specialist and demanding linear applications. (specialist satellite roller screw web page)

There are two main satellite roller screw nut designs;

Type - RV AND BRV
When the screw turns, the satellite rollers move as the lead on the screw. In this execution the rollers are in constant contact with the thread of the screw and the thread of the nut. The rollers do not move axially relative to the nut and are not recycled. Due to its design this execution is particulary suitable for applications where high axial loads, high speed, and high feed speeds are requested. RV and BRV may be distinguished from each other by the execution of the screw. The RV screw has a ground thread whereas the BRV has a precision rolled one.

Type - RVR
The RVR execution is designed for small leads and is used where a high positioning precision is required in association with high stiffness and heavier axial loads. As the rollers are recycled after each of their revolutions, this design is not suitable for high speeds.

The key product advantages are:

  • Heavy axial loads for a small diameter screw
  • Nut designs with extreme long life
  • High efficiency
  • No-backlash standard high stiffness linear precision up to 6 µm / 300 mm
  • Can accept a high rotary speed (system RV and BRV without roller return type)
  • Extremely small leads can be supplied on large diameter screws (system RVR with roller return design)

If you require further technical information, please do not hesitate to contact our sales engineers who will be more than happy to help you with your selection. Alternatively download the relevant linear catalogue from the download button at the top of this page or use the following link to request a printed catalogue or a CD version. CD/Catalogue

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