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3D-finishing of metal components manufactured by the powder bed fusion process
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School of Engineering |
G5 Artikkeliväitöskirja
| Defence date: 2025-09-19
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en
Pages
69 + app. 85
Series
Aalto University publication series Doctoral Theses, 163/2025
Abstract
Laser-based Powder Bed Fusion (PBF-LB) is a promising additive manufacturing process for producing high-performance industrial components. However, achieving strict geometric product specifications (GPS) with dimensional tolerances of 10–50 μm remains a challenge, particularly for demanding applications such as injection molds, combustion engine pistons, and paper rolling machines. The absence of standardized machining allowances for PBF-LB components and the limited understanding of geometric deviations during post-processing further hinder its industrial adoption. To address these challenges, this study investigates machining allowances for 3Dfinishing of metal components manufactured via PBF-LB and examines the influence of process parameters on geometric deviations.
A mixed-method approach is employed, integrating case studies, laboratory experiments, and finite element method (FEM) simulations. Full factorial testing is conducted for AlSi10Mg and maraging steel, examining anisotropy in mechanical thread strength and surface characteristics. Additionally, a previously unexplored thermo-mechanical FEM simulation model is developed and validated to predict cumulative geometric deviations during the PBF-LB process and after support removal process.
The study reveals that AlSi10Mg exhibits higher warpage and anisotropy than maraging steel. However regardless of material, factors such as variations in energy input, staircase effect, and transition of melt pool stripe overlap to layer overlap impact the physical properties of end-products. Product orientation significantly impacts mechanical thread strength and surface properties. Machining allowances of at least 0.3 mm for linear features and 0.7 mm for curved surfaces are recommended. Additionally, the study finds that manufacturing setup misalignment contributes to geometric deviations alongside residual stresses. The validated FEM model predicts geometric deviations with an error margin of less than 30%, with further improvements possible through optimized mechanical contraction parameters. These findings inform comprehensive design guidelines that integrate machining allowances and predictive modeling for 3D finishing of PBF-LB metal components.
A key limitation of this study is the need for a more robust method to accurately determine mechanical contractions induced during the PBF-LB process. Future research should explore material removal simulations, including side milling, to assess machining-induced deformations. Furthermore, incorporating setup misalignment and heat treatment simulations into FEM models could refine geometric deviation predictions for enhanced accuracy.
Description
Supervising professor
Niemi, Esko, Prof., Aalto University, Department of Energy and Mechanical Engineering, FinlandThesis advisor
Laakso, Sampsa, Assoc. Prof., University of Turku, FinlandAkmal, Jan, Asst. Prof., Aalto University, Department of Energy and Mechanical Engineering, Finland
Other note
Parts
- [Publication 1]: Ullah, R., Akmal, J.S., Laakso, S.V.A., & Niemi, E. (2020b). Anisotropy of additively manufactured AlSi10Mg: Threads and surface integrity. International Journal of Advanced Manu-facturing Technology, 107(9–10), 3645–3662. Scopus.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202004282927DOI: 10.1007/s00170-020-05243-8 View at publisher
- [Publication 2]: Ullah, R., Akmal, J.S., Laakso, S.V.A., & Niemi, E. (2020a). Anisotropy of additively manufactured 18Ni-300 maraging steel: Threads and surface characteristics. Procedia CIRP, 93, 68–78.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202010025771DOI: 10.1016/j.procir.2020.04.059 View at publisher
- [Publication 3]: Ullah, R., Lian, J., Akmal, J., Wu, j., & Niemi, E. (2023). Prediction and validation of melt pool dimensions and geometric distortions of additively manufactured AlSi10Mg. International Journal of Advanced Manufacturing Technology, 126(7), 3593–3613.
Full text in Acris/Aaltodoc: https://urn.fi/URN:NBN:fi:aalto-202304122720DOI: 10.1007/s00170-023-11264-w View at publisher
- [Publication 4]: Ullah, R., Akmal, J.S., Laakso, S.V.A., & Niemi, E. (2025). Part-scale finite element simulation and investigation of machining allowances for complex products manufactured by laser-based powder bed fusion. Submitted to International Journal of Computer Integrated Manufacturing (2025)