Computer aided system for tolerance allocation and verification CASTAV

Tolerancing appears in every phase of the product life-cycle from design through manufacture to inspection. The objective of this work is to design and develop a tool to help designers evaluate alternative design, manufacturing and assembly solutions from the tolerance standpoint, at an early stage of product design. This paper describes the structure of the computer aided system for tolerance allocation and verification (CASTAV) system. CASTAV integrates a CAD system, a knowledge based system (KBS) and mathematical procedures. The CAD system is used to extract geometric information at both assembly and part layout levels and construct tolerance elements such as dimension chains for length fit analysis. The KBS, based on an object-oriented approach, embeds the tolerance knowledge and a user interface. The mathematical procedures are used for the tolerance determination based on optimisation models. The integrated tolerance system aims to help designers enhance their tolerance knowledge and perform tolerance tasks efficiently. The tool represents a step towards concurrent engineering