ABSSAC 2019 Satellite roller screws

  • Published: Wednesday 19th December 2018
  • Updated: Monday 16th December 2019

With a traditional recirculating ball screw design, the captivated ball bearings within the nut housing transfer the load (force) between the screw and nut. This ordinarily means that in order to increase the load capacity, but remain with the same sized screw; you have to change the ball nuts physical parameters. Firstly, an increase in the amount of ball bearings physically touching the load surface of screw and nut within the nut housing will increase its load capacity. This can be done by increasing the amount of times the ball bearings recirculate within the ball nut housing, but the playoff of this change normally means a larger diameter nut housing or a longer nut housing. To this effect, the ball nut size versus its load capacity will always be apposing each other. It is true to say that 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 a large advantage, which ultimately translates into a high load transfer capability.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.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 as a consequence, their lifespan can be up to 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.