Kinematic Couplings For Rapid and Repeatable Positioning

Who to contact for more information:
Martin L. Culpepper Prof. Alex Slocum
617-258-8541 617-253-0012

Related U.S. Patents:

5678944 : Flexural mount kinematic couplings and method
5769554 : Kinematic coupling method and system for aligning sand mold cores and the like and other soft objects and surfaces

See a presentation on kinematic coupling research

What are they? A kinematic coupling is a device used to repeatably position components often with sub-micron repeatability.  A traditional kinematic coupling consists of three "sphere" shaped members mounted to one component and three corresponding "v-shaped" grooves attached to, or machined into the other component.

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Traditional Kinematic Coupling

How they work. To deterministically locate two components, 6 relative degrees of freedom (3 translation & 3 rotation) must be constrained.  To do so, exactly 6 points of contact between the two components are needed.  In a traditional kinematic coupling, this is accomplished through 2 points of contact at each sphere - groove joint.

KC_DOF.gif (9232 bytes)

6 Relative DOF

Performance It is difficult to give a concrete number for the repeatability of a kinematic coupling as this is dependant upon many factors:
  • Application
  • Applied pre-load
  • Working load(s)
  • Sphere dimensions
  • Sphere material
  • Groove dimensions
  • Groove material
  • Others

However, the repeatability of kinematic couplings has been measured as low as 0.02 micronsThis is less than the wavelength of visible light!

Applications Kinematic couplings can be used in most applications which require repeatable location.  Examples include:
  • Product Fixturing
  • Machine/Robot Alignment
  • Pallet Stacking
  • Casting/Molding (see flexural kinematic couplings)
  • Tooling Location/Fixture
  • Alignment in Assembly Processes (see flexural kinematic couplings)
  • Location of CMM Parts
  • Others....