Quantifying Automated Tooling Wear and Kinematic Registration Tolerance Stack-Up
Quantifying automated tooling wear requires integrating Archard degradation rates into 6-DOF kinematic vector loops to predict dimensional stack drift.
Kelvin Mount
Meaning
Precision mechanical interfaces employ a three-point kinematic configuration consisting of a sphere in a cone, a sphere in a v-groove, and a sphere on a flat surface to constrain all six degrees of freedom. In optical and metrology instruments, using a kelvin mount provides a highly stable and repeatable interface that allows components to be removed and replaced without losing alignment. This configuration isolates the mounted component from thermal expansion and stress in the supporting frame.
Constraint Scheme
The cone provides three points of contact, the v-groove provides two, and the flat surface provides one, summing to the exact six constraints required. When assembling a kelvin mount, the forces holding the spheres against their seats must be carefully controlled to prevent slippage. This arrangement ensures that there is no over-constraint of the mounted plate.
Load Sensitivity
High contact stresses occur at the interfaces due to the very small contact areas of the spherical surfaces. Utilizing hardened materials for both the balls and the seats prevents the local yielding that would destroy the precision of the mount.
Practical Application
The asymmetry of the three seats means that the mount is highly sensitive to the direction of applied forces.