A CAD method for tolerance allocation considering manufacturing difficulty based on FMECA tool

In a product life cycle, the tolerances present major impacts on the quality and cost of mechanisms. This paper presents an innovative methodology for tolerance allocation. The proposed approach allows tolerance integration in a computer-aided design (CAD) model, while considering functional and manufacturing requirements in an early phase of digital mock-up (DMU). The purpose is to consider the manufacturing process in the tolerance allocation using tools for the study and analysis of reliability of the design or the process, as the Failure Mode, Effects and Criticality Analysis (FMECA) and Ishikawa diagram. The results lead to the broadening tolerance values of difficult machined dimensions while respecting the functional requirements. Thus, the total cost of assembly decreases. The model is validated through a case study of tolerance allocation using various approaches.