Flexibility assessment in continuous manufacturing processes based on a physics-informed digitalisation strategy: A case study in the rubber industry

This study develops a physics-informed digitalisation strategy to assess potential flexibility from different perspectives in continuous manufacturing processes. As a case study, the co-extrusion process of sealing profiles for the automotive industry is chosen. This process operates continuously for 3–5 days to manufacture one sealing profile, consuming considerable energy, which is influenced by the process conditions set during the manufacturing line start-up. Increasing flexibility can contribute to a more sustainable and energy-efficient manufacturing industry. However, since process conditions directly affect the final quality and properties of the manufactured profile, any modifications must be preceded by a thorough analysis of their implications based on the sealing profile geometry, different line velocities and product quality tolerances. Computational Fluid Dynamics (CFD) techniques are used to model the co-extrusion process, while Finite Element Methods (FEM) are applied to model product quality and temperature dependencies. A Reduced Order Model (ROM) is developed for both FEM and CFD models, and the developed model enables the assessment of optimal process parameter adjustments to accommodate line velocity changes at different product quality tolerances. The results prove that the variation of the line velocity can provide process flexibility to the industry (around ± 30 % in total electrical power for ± 20 % variation in the line velocity). Besides, a 20 % increase in line velocity results in a 5.5 % reduction in total CO₂ emissions and a 5.2 % decrease in energy costs, suggesting that operating at higher line velocities is more energy efficient. The proposed strategy also analyses the potential flexibility depending on the product quality tolerance and the utility prices. The results show that increasing the allowable quality tolerance reduces the overall power consumption, with the largest potential in thermal power reduction. Beyond the analysis of one manufacturing line in operation, flexibility can be achieved by adequately scheduling several profiles with different electrical-to-thermal power ratios. In addition, a convenient redesign of profiles can also be used, as profiles with thinner walls and less rubber allow more flexibility, although they consume more electricity in the extruder.