Recently, satellite roller screws were required to replace recirculating ball screws within an pharmaceutical application involving the high pressure extrusion of a substrate material. The application involved the enhanced manufacture of tablet form medication, but required precision axial accuracy as well as greatly increased axial thrust requirement. The existing design was limited by physical space in which the product could operate, which had meant that a larger ball screw design could not be used to overcome the high axial thrust requirement.
Using the standard Rollvis RV series, meant that the physical roller screw's nut diameter could in fact be significantly smaller than the original ball nut design, which translated into less unit cost.
The satellite roller screw product has precision rollers instead of ball bearings in the nut housing. The rollers transmit the load between the nut and the screw and since the rollers are constantly engaged with the threads of the screw, results in a high number of contact points, which ultimately, allows the satellite roller screw to support heavier axial loads.
Interestingly, when the screw turns, the satellite rollers move as the lead on the screw and the rollers do not move axially relative to the nut and are not recycled. Additionally, roller screws have much greater longevity and can enable up to 4 times the axial thrust capacity for the equivalent sized ball nut screw design.
Applications to date have included flight critical aerospace apparatus, medical operating equipment and advanced machine tool operations, in some cases complete hydraulic systems have been replaced with intelligent motor control and roller screw linear movement. A satellite roller screw employs matched rollers to rotate (or satellite as the product name suggests) around the screw thread during actuation instead of ball bearings. By design, there is an immediate increase in the physical amount of contact points on the screw that can support a load compared with that of the same diameter ball screw. The satellite roller screw is therefore primarily chosen as part of a transition within a new or existing design to achieve greater load capacity and greater linear positional accuracy, in the smallest envelope space. A roller screw design will always transmit more load than a ball screw nut assembly size for size.
ABSSAC has been the UK distributor for Rollvis satellite roller screws for many years and over that time they have successfully placed the product in numerous applications. The ability to take a standard part and totally customise the design to suit the application is a key advantage to the product.
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