Novel design of a kinematic coupling precision fixture for repeatable multiple-inclined repositioning

In precision manufacturing, the demand for positioning solutions that enable accurate and precise positioning and repositioning of one object relative to another is critical. Current state-of-the-art solutions employ expensive motorized chucks or stages that provide near-continuous variation in position or rotation with a final resolution and precision that largely depends on the accuracy of the control of said motorized units. Other less versatile, but simpler solutions make use of basic kinematic coupling principles taking advantage of the deterministic nature of the positioning they provide. The work presented here combines the rotational flexibility of a motorized chuck while maintaining the high precision of a deterministically defined positioning concept obtained through kinematic coupling principles. By using multiple sets of radially distributed three vee-grooves paired with three spheres on two different wedge-shaped bodies, it is possible to change the inclination of the top plane of the upper wedge with regards to the bottom plane of the lower wedge solely by rotation of the two wedge-shaped bodies relative to one another. The developed apparatus has been manufactured in stainless steel 316L and evaluated using a tactile coordinate measurement machine showing xyz single-digit micrometer range repositioning repeatability, as well as an inclination angle with average of the variances of 10 μrad for 10 repeated measurements of seven different angles respectively. Lastly, the apparatus has been tested in a measurement setup for a laser scanning confocal microscope showing little need for training of the user, while providing a degree of flexibility and repeatability usually only achievable with complex goniometer systems.