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

Abstract

Additive manufacturing 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 a certain company. Factors such as the material used, part dimension, geometrical features, as well as tolerance requirements contribute to the overall manufacturing costs that 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 are 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 [DIN ISO 2768-1, Allgemeintoleranzen—Teil 1: Toleranzen für Längen- und Winkelmaße ohne einzelne Toleranzeintragung (1991). Accessed 26 February 2018; DIN ISO 2768-2, Allgemeintoleranzen—Teil 2: Toleranzen für Form und Lage ohne einzelne Toleranzeintragung (1991). Accessed 26 February 2018].

Physical and Geometrical Properties of Additively Manufactured Pure Copper Samples Using a Green Laser Source

“…To analyze the dimensional accuracy for certain features such as cylinders, overhangs, and walls, a benchmark geometry developed by the Fraunhofer Institute for Material and Beam Technology IWS within the AGENT-3D program was built and analyzed via 3D scanning using an ATOS Core GOM 135 (GOM GmbH, Braunschweig, To analyze the dimensional accuracy for certain features such as cylinders, overhangs, and walls, a benchmark geometry developed by the Fraunhofer Institute for Material and Beam Technology IWS within the AGENT-3D program was built and analyzed via 3D scanning using an ATOS Core GOM 135 (GOM GmbH, Braunschweig, Germany) which can be seen in Figure 2. The geometry and previous measurements with 3D scanning and computed tomography (CT) were described in detail by Lopez et al [24] and Gruber et al [25]. To analyze the dimensional accuracy for certain features such as cylinders, overhangs, and walls, a benchmark geometry developed by the Fraunhofer Institute for Material and Beam Technology IWS within the AGENT-3D program was built and analyzed via 3D scanning using an ATOS Core GOM 135 (GOM GmbH, Braunschweig, Germany) which can be seen in Figure 2.…”

“…To analyze the dimensional accuracy for certain features such as cylinders, overhangs, and walls, a benchmark geometry developed by the Fraunhofer Institute for Material and Beam Technology IWS within the AGENT-3D program was built and analyzed via 3D scanning using an ATOS Core GOM 135 (GOM GmbH, Braunschweig, Germany) which can be seen in Figure 2. The geometry and previous measurements with 3D scanning and computed tomography (CT) were described in detail by Lopez et al [24] and Gruber et al [25].…”

Diffraction-Based Residual Stress Characterization in Laser Additive Manufacturing of Metals

“…One of the main advantages of the LMD process is that in contrast to other processes the excess material is minimized, even though material loss can still be a problem due to overspray of the nozzle [65]. In addition, the deposition rates are higher during LMD, but the overall part quality typically suffers compared to LPBF [66]. The most relevant process parameters for process optimization are powder or wire feed rate, laser power, gas flow and scanning velocity [67].…”

Electron-Optical In Situ Imaging for the Assessment of Accuracy in Electron Beam Powder Bed Fusion

“…The accuracy of AM processes is usually assessed by manufacturing of benchmark artifacts [ 1 , 2 , 3 ] with standardized and differently sized geometrical features. For metal powder bed fusion, Gruber et al [ 4 ] showed that the obtained accuracy of the manufactured artifacts could be related to basic process characteristics like beam diameter and layer height. However, also the feedstock material and the quality of the corresponding process parameters strongly affected the results [ 4 ].…”

“…For metal powder bed fusion, Gruber et al [ 4 ] showed that the obtained accuracy of the manufactured artifacts could be related to basic process characteristics like beam diameter and layer height. However, also the feedstock material and the quality of the corresponding process parameters strongly affected the results [ 4 ]. The strong influence of process parameters has also been shown by Smith et al [ 5 ] for the dimensional accuracy of truss structures manufactured by PBF-EB.…”