Discrete event simulation tool for analysis of a manufacturing system : Observed from a context of sustainability and efficiency

Abstract: This report is a master thesis project done as a final project of Industrial design engineering with a master in production engineering, at Luleå University of Technology during the spring of 2021. The project was done as a collaboration with the company Nord-lock, based out of Mattmar, Sweden. The company produce wedge-locking washers that use tension instead of friction to secure critical bolted joints. The purpose of the project was to create a simulation model which can be used as a tool for improving production utilisation. The company do not currently use simulation within the organisation, requiring the model to be built up from scratch. The overall project structure has followed a cyclic process which divides it into three different laps. The first lap focused on mapping the production and gaining an understanding of the manufacturing and business systems. The second lap focused on the creation of the simulation model and further data collection. The third lap looked into validation and experimentation with the simulation model, creating cases to test the use and outputs of the model. The simulation model followed four key stages for conducting a simulation study, going from creating an understanding of the real world and the problems to the solutions.  The current state was mapped using different methods for data collection and further analysis of the findings. Direct observation with operators at the shop floor was used to gain an understanding of how a batch travels through the manufacturing system. Observing the human operations that are required for different activities was important for creating a map over the necessary steps in a process. The production is divided into two different flow groups, with machines and operations being placed into machine groups under these. The surface treatment is an important step in assuring the products quality and exists as a collection of machine groups under the first flow group. It became clear that the production planning of batches was separated between the two flow groups, creating a disconnection to how a batch travels through the entire manufacturing system. The simulation model would aim to allow batches to be planned from creation to finished product, observing how they behave through the system.  Due to limited experience of the simulation software within the company, the creation of the model into a tool required control of inputs being accessible to the intended users. The inputs and outputs of the system are therefore controlled using excel sheets which only requires a user to have experience with excel and the existing business systems. Data for activities within the simulation model is gathered from the business systems, which gets their data from the results of the actual manufacturing system. A user guide was created to assist users with adding new articles or change data into the simulation model. The excel sheet which displays the outputs of the system is connected to the simulation model and updates as the model is run.  The simulation model showed that the surface treatment is a big bottleneck for the throughput of the system. Subsequent cases that were created experimented with how this bottleneck react to different inputs. When increasing the throughput time of the machine groups before the surface treatment, no real increase in the throughput of the system was found. The queue time before the bottleneck decreased greatly when comparing the results to the regular model. The second case observed how the system reacts to changes in the surface treatment, comparing the results to the previous case. The final chapter discusses how the tool can be used within the company. A sustainable context is used to show how different results can affect the sustainability within the manufacturing system in all three aspects.