Continuous research and development ensure the production of high-quality steel which is a key component in society and people’s everyday lives. Computational fluid dynamics is used in R&D to optimize the flow control during production. Generating a high-quality mesh while maintaining a reasonable cell count has significant impact on the equilibrium between computational cost (i.e., time and memory) and accuracy. The traditional approach when meshing the nozzle and mould is using a combination of hexahedral elements for the simple mould geometry and tetrahedral elements for the complex nozzle. However, building the coupling between these cell types is challenging and inefficient. The present study examines the possibility of using a hexahedral-polyhedral combination or a full polyhedral mesh instead of tetrahedral cells to decrease the amount of elements and improve accuracy (e.g. improved skewness, smoothness, orthogonality, etc.) with less computational cost. Finally, the resulting mesh is tested as part of a state-of-the-art digital model of a real industrial caster with the aim of facilitating the flow optimization.