Computing clearances and deviations in over-constrained mechanisms

Abstract A manufactured over-constrained mechanism can’t be assembled and can’t be mobile without clearance in its joints. During the conceptual design phase, designers must specify the degree precision for the parts without proper quantitative decision-making tools. Those decisions have a great impact on the product’s quality and cost. In this paper, clearance and deviation are defined for an assembly of rigid parts. A geometric model is presented to measure those values in a given mechanism using the TTRS model. Optimum values are computed by minimizing a weighted function of both clearance and deviation.