Integration of tolerances in the mechanical product process: Assembly with defects modelling.

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Title: Integration of tolerances in the mechanical product process: Assembly with defects modelling.
Author: TLIJA, Mehdi; LOUHICHI, Borhen; BENAMARA, Abdelmajid
Abstract: In the digital mock-up, parts and assemblies are used in ideal configurations. In fact, tolerances are represented as annotation on the CAD model and tolerances stack-up is not considered during the optimization of mechanical system assemblability and F.E Analysis. Then, the improving of the numerical model requires consideration of tolerances in the CAD model. An approach to incorporate dimensional and geometrical tolerance in CAD model is developed. Indeed, models, that allow obtaining assemblies with defects, are realized. In a bottom-up design process (component-to-assembly), the proposed model founds components with defects allowed by tolerances. Components with defects are deduced from the combination of two model sets which are obtained by using two sub-algorithms. A first sub-algorithm incorporates dimensional tolerances in CAD model. This model founds relationships between component dimensions (driving and driven dimensions) and performs a three dimension tolerancing chain by a technique based on connected graphs. The second sub-algorithm tacks into account geometrical tolerances in CAD model. Tolerance zone is discretized by parameters deduced from deviation torsor of toleranced element. This discretization allows obtaining possible realistic configuration of the toleranced element. Then, face movements are realized to obtain components with defects. Thus, assemblies with defects can be obtained by performing various combinations between components with defects. Nevertheless, the assembly regeneration, with realistic components, requires redefining assembly mates which are initially assigned to nominal assembly. Then, a new approach to defining realistic assembly mates in the case of rigid assembly is presented.
Subject: Tolerancing; CAD model; Assembly with defects; Assembly mates; Conception robuste (S9)
Publisher: AFM, Maison de la Mécanique, 39/41 rue Louis Blanc, 92400 Courbevoie, France(FR)
Date: 2013-12-20

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