Tolerancing is an important issue to boost the levels of circular economy such as the ecosystem. This study introduces a combined tolerance allocation optimization approach for mechanical assemblies with interrelated dimension chains. The proposed method is based on Genetic Algorithm (GA) and Difficulty Coefficients Computation (DCC) simultaneous. The proposed GA objective function is to minimize total cost constrained by the equations of functional requirements. These equations are the tolerance dimension chains considering difficulty coefficients. The computation of manufacturing difficulty is based on the Failure Mode, Effects and Criticality Analysis (FMECA) tool and Ishikawa diagram. The proposed optimization approach named (GADCC) is applied to mechanical assemblies with interrelated dimension chains taken from previous article and compared to their tolerance optimization methods. The suggested total cost comprises both the manufacturing cost and the cost associated with Taguchi quality loss. The analysis of obtained results demonstrates that the proposed approach leads to help the manufacturing of problematic dimensions by broadening their tolerances while respecting the functional requirements. Consequently, the defect rate of manufacturing parts is reduced. This is allowed to deduce that the GADCC model is an economic and efficient tool of tolerance allocation in a circular economy perspective.
