Due to a global increase in competitiveness in manufacturing,companies strive to increase the effectiveness of their manufacturing systems. The new industrial revolution, Industry 4.0, is a consequence inmotion to aid in creating improved manufacturing systems. A common tool within Industry 4.0 is simulation, where one could simulate changes in a virtual representation of a real world system. Discrete Event Simulation (DES) is a tool that has been widely adopted within industries to test manufacturing system changes virtually before implementing them physically. However, there is a need to discover the advantages, disadvantages and barriers to the application of simulation modeling in industry, as well as how to show the value with using the technique. A case study at the global manufacturing company Atlas Copco's plant In Tierp, Sweden has been undertaken with the purpose of using DES to aid a manufacturing plant in improving a manual manufacturing system, and how this could develop the current approach to a more long-term and sustainable one. Process mapping have been used to facilitate better understanding of the system prior to simulation modeling, as a manual system proved to be difficult to map otherwise. The results of this study points to that simulation can provide advantages of that decisions regarding implementation of system improvements could have better basis for being taken, simulation can be used to test system changes virtually to prevent eventual implementation problems, and simulation can be used as a tool to generate long-term solutions. However, disadvantages and barriers were identified as resistance from management in difficulties to convince the value of using simulation, extensive modeling competency required, and lack of the right prerequisites makes simulation modeling implementation more difficult. Further research should focus on uncovering the difficulties and barriers to the implementation of simulation modeling in industry, as this was not widely discussed in existing literature.