Lean and Agile Precision Manufacturing Systems

摘要

A quasi-kinematic coupling (QKC) is an alignment interface that can be used to make low-cost assemblies with sub-micron precision and/or sealing contact. Unlike kinematic couplings that rely on point contacts formed by mating balls in v-grooves, quasi-kinematic couplings are based on arc contacts formed by mating three balls with three axisymmetric grooves. Though a quasi-kinematic coupling is technically not an exact constraint coupling, proper design of the contacts can produce a weakly over constrained coupling that emulates an exact constraint coupling. This paper covers the practical design of quasi-kinematic couplings and derives the theory that predicts quasi-kinematic coupling stiffness. A metric of over constraint is presented and used to develop recommended practices for minimizing the over constraint in quasi-kinematic couplings. Experimental results are provided to show that quasi-kinematic couplings can provide repeatability (1/4 micron) that is comparable to exact constraint couplings.