Integrated tolerancing process for conceptual design

For car and aircraft industries, the management of geometrical variations has become an important issue in product design process and concurrent engineering. Indeed, designers need to manage dimensional and geometrical tolerances and to know information that contributed to their determination. The goal here is to put tolerancing in a concurrent engineering context. There are important questions that would need to be looked upon: How to integrate the tolerance synthesis in the design process? How to ensure the transition from function to geometrical specifications on parts? How to keep traceability of tolerances during the design process? Few answers exist today in academic works and there are few supports in CAD systems. Therefore, to build a coherent data model taken into account tolerances, we describe in this paper a multi-level approach that enables a tolerancing process integrated with conceptual design. The first level integrates information relating to functional aspects of an assembly. The second describes the structure of the assembly, and concerns the integration of functional needs and technological solutions. The last level translates functional requirements into geometrical requirements between/or on parts of the products, and provides the geometrical specifications on each part satisfying the geometrical requirements. This multi-level architecture is represented as an object oriented data model based on UML (Unified Modelling Language) that enable data management for functional tolerancing in design and keeping traces when querying about data.