Kinematic Couplings.
Analysis of repeatability metrics and the physics of cone-and-groove location interfaces.
Exact Constraint Design
A rigid body in space has exactly six degrees of freedom (DOF): translation along X, Y, Z, and rotation around those axes (pitch, yaw, roll). A kinematic coupling utilizes "exact constraint" design, establishing exactly six points of contact to perfectly arrest all six DOFs.
Because there is no over-constraint (no fighting between redundant locating pins), thermal expansion or minor manufacturing deviations in the mating pallets do not induce stress or distortion. The pallet simply settles perfectly into place.
Zero-Point Workholding
Modern zero-point systems (e.g., Schunk, Lang) rely on these principles combined with hydraulic or pneumatic drawbars. They allow a vise or fixture plate to be removed from a machine and re-installed with a positional repeatability often exceeding 0.0002" (5 microns).
The economic impact of this is profound: setup time is moved offline. The machine spindle is never waiting for an operator to indicate a vise. Spindle utilization increases from a typical 30% to over 70%.