Simulation-based capacity analysis of a battery foil production facility – A study at Gränges in Finspång

Sammanfattning

The green electrification boom within the automotive industry has led to a significant increase in demand for materials used in battery manufacturing, where aluminum foil is a key component in lithium-ion batteries. Gränges is a Swedish industrial company operating globally within the aluminum industry, producing rolled aluminum for various industrial applications, primarily within the automotive sector. To meet the growing demand, the company has built a new production facility in Finspång focused on the production of battery cathode foil. The purpose of this study has been to investigate how the production capacity of the battery foil plant is affected by different investment alternatives and experimental factors. The objective has been to provide decision support for future investments during the ongoing ramp-up phase, where processes and workflows are not yet fully stabilized. To analyze the system, a simulation study was conducted in which the current production system. Simulation was chosen as the method due to the system’s complexity, consisting of multiple interconnected subsystems, and the need to analyze future scenarios involving changes in machinery and process parameters. The simulation model was initially validated against the current production by using existing parameters and shift schedules to ensure that it produced realistic material flows and throughput. The model was then used to analyze the system under stable operating conditions after ramp-up. These scenarios were evaluated across different levels of three experimental factors: proportion of half coils, mother coil change time, and yield. The results show that, in the base scenario, the plant can produce approximately 217 tons of approved material per week out of a total of 281 tons produced, assuming a mother coil change time of 1 hour, a yield of 77%, and a half coil proportion of 5%. This aligns well with the company’s internal estimates. Several investment scenarios were also analyzed, where additional cold rolling mills and slitting lines were introduced into the system. The results showed that the system could produce approximately 249 tons of approved material per week out of a total of 323 tons produced. The conducted effect analysis revealed that mother coil change time and the proportion of half coils had the greatest impact on overall system capacity and throughput, while yield primarily affected the amount of approved material rather than total production volume. This implies that improvements in yield increase the volume of sellable products without increasing system capacity in terms of tons per week. The study also shows that investments in new machinery do not automatically lead to increased production capacity. In some scenarios, investments initially resulted in lower capacity for battery foil production compared to the base system. This can partly be explained by the current use of a simplified model of cold rolling mill 2712 from another part of the facility, meaning that battery foil production currently draws capacity from existing production flows. By investing in dedicated resources for battery foil production, the dependency on mill 2712 can be reduced, thereby freeing up capacity for other production flows at the site and potentially improving the overall production capacity of the entire facility. The results also indicate that system balancing, such as adding buffer capacity and improving the distribution of workload between machines, is crucial for investments to achieve the desired effect. In summary, the study shows that investments in additional machinery, combined with improved system balancing, can increase the capacity of the battery foil plant while reducing dependency on existing production flows. The results also highlight that mother coil change time and the proportion of half coils are the most influential factors affecting system capacity and should therefore be carefully considered in future investment decisions. Yield mainly affects the amount of approved material and not the overall throughput.