Analysis of the near flatness phenomenon for multi-loop closed manufacturing systems

With the recent development of the electrical vehicle (EV) industry, the study of manufacturing systems producing key components in this sector is becoming increasingly important. Multi-loop closed manufacturing systems (MCMS), whose operation and control are rarely studied in the literature, are widely used in the EV industry. This work provides innovative guidelines for MCMS operation also valid in a general context and not necessarily limited to the EV field. The main focus is on a specific topic of MCMS operation, namely the near flatness phenomenon. The near flatness indicates how system throughput is influenced by its population, i.e. the number of items circulating in the MCMS, especially in high-throughput conditions. The study of near flatness aims at enhancing MCMS flexibility in terms of population control and handling while guaranteeing high system throughput. In this work, a new indicator quantitatively describing the near flatness is provided. Numerical studies are conducted to analyze the effect of machine efficiency in isolation, mean times to repair and buffer capacities on the near flatness. Experiments are also carried out on a real case of MCMS in the EV field. Based on the experimental results, practical specifications to improve MCMS design and management are provided.