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The University of Southampton
Rifi An Enterprise Consultancy Unit

Case Study: Tribological investigation of worm gears in actuators

Objective: To enhance the performance of worm gear lubrication in order to increase the efficiency of actuator systems.

Situation

  • Rotork Controls Ltd manufacture actuators that uses worm and wheels gears for its operations.
  • Worm gears are used to reduce speed and increase power when large gear reductions are needed.
  • The efficiency of worm gears is known to be severely compromised by the high friction generated within the sliding contact due to poor lubrication.
  • Rotork realised that to improve the design and hence efficiency of next generation actuators, an understanding of the lubrication parameters that define the elastohydrodynamic characteristics within the worm/wheel sliding contact was required.
  • What we did

  • The major challenge of this project was to produce a mathematical model that identify the lubrication regimes of the worm gears used in the design of Rotork's actuators.
  • This required an in-depth understanding of the contacting gear surfaces and properties of the lubricants employed by Rotork.
  • To investigate the surface profile of the gear teeth, state-of-the-art, non contact, surface profilometary (TAAICAN) was employed (developed at University of Southampton).
  • The properties of the lubricants and gear materials were measured in our Tribology Laboratory, in the national Centre for Advanced Tribology at Southampton (nCATS), using the latest facilities available.
  • Impact

  • The laboratory test results were fed into the elastohydrodynamic  equation, which clearly defined a range of bespoke lubrication regimes for Rotork worm/wheel gear contacts.
  • The outputs of the model were validated using a pin on disc experiment that simulates the gear contacts.
  • The outcome of the project has helped Rotork to understand, in more detail, the impact of lubrication type and lubrication regimes on the performance of the worm gears within their actuators.
  • At the conclusion of the project, Rotork is now initiating design improvement strategies that will significantly improve the efficiency of their actuators.  The outcome of this project has also helped to inform the design of new generation high speed actuators that will give Rotork an edge over their competitors.
  • Actuator
    Actuator
    Worm & wheel gear
    Worm & wheel gear

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