A tri-objective model for the manual assembly line design integrating economic, technical and ergonomic aspects

Smart assembly lines are a milestone of Industry 4.0 allowing the efficient and effective production of complex products with an acceptable time-to-market. According to the literature and the standard practice, these lines are made of a set of equipped stations with a worker for each of them. Products flow the stations in sequence to perform their assembly cycle. Nowadays, the best design of assembly lines deals with the joint inclusion and best mix of multiple dimensions, often in conflict and requiring good trade-off solutions. This paper proposes and preliminary applies a tri-objective linear programming model to design a single-model smart assembly line aiming at optimizing the system annual equivalent cost, the time balance among the stations and, finally, the level of fatigue each worker is exposed. Details on the model boundaries are given together with its full mathematical formulation and linearization, to reduce its complexity. Finally, a preliminary case study links the model to practice showing its feasibility and potential benefit for the modern smart industries.