The single-screw extrusion process is used to produce plastic films. Therefore, the polymer melt is transferred from a round cross-section at the end of the single-screw extruder to a flat shaped rectangular cross-section by a special sheet die. For high product quality, the engineering design of sheet dies is of crucial matter. Today, the design process and the prediction of flow are done by the use of Computational Fluid Dynamics (CFD). The design process itself is in general quite complex. In addition to that, different software is used for geometry creation, meshing and execution of simulations, which increases the necessary process steps and numerous software interfaces. To achieve a higher performance and less risk of errors, a novel method was developed in this study, to optimize the so-called coat-hanger die. The new method eliminates the step of geometry creation and directly generates the CFD-mesh by parameterization. For comparing reasons, CFD-simulations based on the common and new method were performed and evaluated to optimize a coat-hanger die by means of fluid dynamics. The efficiency of the design process significantly increased compared to nowadays common methods. Even in comparison to a parameterized CAD-file, the time for tool design could be substantially reduced.