Robust additive manufacturing of components with thin walls and narrow

On one hand, the industry must utilize flexible manufacturing processes to increase production agility and resilience. On the other hand, to be able to meet stringent customer requirements the industry can only adopt manufacturing methods which are robust and can render predictable product quality.

Investigates the robustness of LPBF

This project investigated the robustness of the Laser Powder Bed Fusion (LPBF) process with a focus on the integrity of thin walls and narrow channels produced with this technology. For parts where the performance is heavily reliant on thin walls (e.g., for heat transfer) and narrow channels (e.g., for fluid transfer) a robust LPBF production that can guarantee fluid tightness, high mechanical strength and dimensional accuracy is critical.

With respect to process flexibility, the LPBF technology offers unique opportunities. With this manufacturing method parts with various designs can be produced simultaneously, with different orientations, and without the need for moulds. In addition, the LPBF technology offers unparalleled possibilities for production of light weight components by enabling fabrication of hollow cavities, thin sections and conformal channels which can be designed to meet customer specific requirements on weight reduction and function.

Represents the complete value chain

The project consortium constructed the complete value chain and benefits from collaboration of key national and international companies. Two end-users (i.e. Alfa Laval, Siemens Energy) with a range of products with functions derived from thin walls and narrow channels were present and set the process requirements.

In addition, the team benefitted from the presence of a material provider (i.e. Höganäs) and three important technology providers in the field of process simulation (MSC Software), production systems (SLM Solutions) and post processing (RENA Technologies). Two service providers with expertise in the field of quality assurance (Nikon Metrology) and product design and process simulation (Etteplan) supported the project.

The industrial team worked closely with RISE Research Institutes of Sweden and Chalmers University of Technology. RISE and Chalmers provided the project with their latest equipment for powder analyses, mechanical testing, AM machinery, monitoring tools, and production related hardware and software. Collectively, the project consortium had access to all equipment, know-how and competence needed to carry-out this project successfully.

The ProThin project was carried out within the strategic innovation program Produktion2030, a joint venture of Vinnova, Energimyndigheten and Formas.

Project results

The ProThin project aimed to develop a novel methodology for evaluating process robustness that is both cost-effective and less reliant on extensive physical testing. This innovative approach utilized predictions from LPBF process simulations, non-destructive quality assessments, and advanced surface refinement treatments.

The fluid separator use case demonstrated three key outcomes: 

1. Process Stability: Combining design for additive manufacturing with process simulations significantly improved LPBF process stability. 
2. Weight Reduction: Optimized designs reduced component weight while maintaining structural strength. 
3. Cost Savings: Strategic component stacking and structures shortened printing time, maximizing yield and reducing costs.

For the guide vanes use case, key insights include: 

1. Deformation Prediction: Commercial simulation tools effectively predicted deformations, aligning with 3D scanning results.
2. Internal Channel Quality: CT scans confirmed homogeneity in internal channel walls. 
3. Airflow Test Results: Airflow tests revealed deviations in sub-1 mm channels, which is likely due to relatively high surface roughness.

Main conclusions

The project demonstrated that simulation tools effectively reduce print failures, therefore, some user groups have adopted these methods in daily process. Simulation tools can also highlight the impact of structure on LPBF costs, aiding in identifying suitable use cases. 

CT scanning proved to be efficient for assessing wall thickness in narrow channels, therefore was considered valuable to be integrated into quality control. 

Improving LPBF reproducibility remains critical. Gas flow significantly affects defect distribution and needs optimization, while powder characteristics impact the process, which require more efficient characterization methods. On-site simulation and quality assessment are key to increasing LPBF adoption, along with robust post-processing tailored to specific materials and features. Powder removal showed little effect on airflow in components with narrow channels, and future work is needed to develop suitable post-processing methods for a range of Ni-based super alloys.

This project offered insights into long-term development with end-users by tackling technical challenges and identifying suitable use cases to accelerate the adoption of LPBF technology.

Published articles

Influence of microstructure and surface topography on material removal by the Hirtisation® process, Rasmus Gunnerek, Gowtham Soundarapandiyan, Michael Christoph Doppler, Eduard Hryha & Uta Klement