Variations and Clearance Computation in Overconstrained Mechanisms

Abstract

Due to manufacturing deviations, introducing clearance is needed to meet both assembly and mobility requirements of the mechanism and make it actually work. However, large clearance influences the mechanism’s accuracy. A wise clearance computation is then crucial. In the present paper, we propose to explicitly determine the minimum clearance values necessary for both assembly and mobility of the system. Compatibility relations will first be determined based on a vectorial modelling of a mechanism and will be used in tolerances and clearance computation. Two concepts will also be defined to help minimising clearance values, ideal mechanism concept and associated mechanism concept. These concepts will be illustrated on a 3D case study: the Bennett linkage.