Comparison of dimensional accuracy and tolerances of powder bed based and nozzle based additive manufacturing processes

Additive Manufacturing (AM) processes have the potential to produce near-net shaped complex final parts in various industries such as aerospace, medicine or automotive. Powder bed based and nozzle based processes like Laser Metal Deposition (LMD), Laser Powder Bed Fusion (LPBF) and Electron Beam Melting (EBM) are commercially available, but selecting the most suitable process for a specific application remains difficult and mainly depends on the individual know-how within in a certain company. Factors such as the material used, part dimension, geometrical features as well as tolerance requirements contribute to the overall manufacturing costs which need to be economically reasonable compared to conventional processes. Within this contribution the quantitative analysis of basic geometrical features such as cylinders, thin walls, holes and cooling channels of a special designed benchmark demonstrator manufactured by LMD; LPBF and EBM is presented to compare the geometrical accuracy within and between these processes to verify existing guidelines, connect the part quality to the process parameters and demonstrate process-specific limitations. The fabricated specimens are investigated in a comprehensive manner with 3D laser scanning and CT scanning with regard to dimensional and geometrical accuracy of outer and inner features. The obtained results will be discussed and achievable as built tolerances for assessed demonstrator parts will be classified according to general tolerance classes described in [1, 2].