Production capacity enhancements through production line simulations

Abstract: The thesis project described in this report was conducted at Scania CV (Scania), which is a global company that delivers transport solutions to customers all around the globe. The project was conducted as a simulation study of the production flow of the output shaft manufacturing line UGA (Utgående Axel), located at the transmission department (DX) in Södertälje. The main objectives for the simulation study was to identify possible enhancements to increase the line-capacity and -OPE, and based on the findings provide a set of recommended actions Scania can take to increase the performance of the production line. To conduct the project was a simulation model developed in another master’s thesis back in 2019 provided to the authors. But since both the production line and the products manufactured at UGA line have been subjected to changes since 2019 was this model outdated and the validity of the model had to be confirmed. Therefore was a thorough current state description developed that was utilized to identify the gap between the simulation model from 2019 and the current state at the productionline. Based on the gap-analysis was it decided that the model from 2019 did not reflect UGA line in its current state to a satisfying degree. Therefore was a new simulation model developed, which then was updated with new input data. During the development of the new simulation model was the old model used as a template where the features that still accurately described UGA line was retained. The new simulation model was validated by a comparison between simulated throughput from the simulation model and historical throughput from UGA line. The validation showed a difference in mean weekly throughput of 0,3 %. It was therefore concluded that the simulation model accurately describe UGA line in its current state. The validated model was then used to simulate a number of different scenarios, and the result was analysed to find different areas for improvements. Finally was the result from the analysis compiled as recommended actions, that in turn was divided into short- and long-term actions. Where the actions categorised as short term concerns actions that could bring improvements to the existing production line, while the long-term actions require reconfigurations of the layout to be realized. The result showed that continue working on decreasing cycle times to achieve the defined goal cycletimes will have a positive effect on the lines capacity, but not on the overall line OPE. The reason for this is that the effect from other losses in the production line will increase when the cycle times become more uniform. But since the capacity will be significantly improved as the goal cycle time is reached, is Scania still recommended to continue their work with cycle time reduction, and if possible reduce the cycle times in some specific machines below the current goal. In addition is Scania in short-term recommended to identify and reduce the undefined stop time that frequently occur, reduce quality losses and improve machine availability. Regarding the long-term actions is Scania recommended to investigate the possibility to reconfigure UGA line. The simulations showed that both increasing buffer sizes at strategic positions to improve bottleneck utilization, or decouple the line to make it less sensitive will positively affect the capacity and OPE. In addition did the simulations of the combination of these two configurations show the greatest improvement among all simulations. Scania is therefore recommended to investigate the business case around either of these configurations or a combination of both.