There is a delicate interplay between process flexibility and process robustness. As the flexibility of a manufacturing process increases, the identification and control of the sources of variation become more challenging. On one hand, the industry must utilize flexible manufacturing processes in order 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.
This project investigates 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.
Despite the unquestionable flexibility of the LPBF process, uncertainty about its robustness has been the major obstacle for industrialization of this technology for serial production. The latest research has identified 175 sources of variation in this technology2. The impact of a number of these sources on the quality of bulk samples has been previously investigated. However, a comprehensive assessment of the impact of the sources of variation on the integrity of thin walls and narrow channels with respect to product realisation is lacking. Consequently, the unique capabilities of the LPBF process have so far been limited to prototypes and have not yet proliferated the industry for serial production of parts for high-performance applications where the full flexibility of LPBF can add considerable value.
A full-scale robustness study is costly and requires numerous print runs and extensive empirical testing. Hence, findings from these investigations are commonly kept proprietary by companies. The objective of this project is to circumvent this issue by developing a new methodology for evaluation of process robustness which is cost effective and less test intensive. This new methodology is based on predictions from LPBF process simulation. The recently commercialized process simulation tools can incorporate material properties, machine data, laser settings, and part design, and are capable of predicting build failure, distortion, porosity, and microstructure. Therefore, by utilizing process simulation it is possible to carry out numerous virtual print runs in order to perform a comprehensive repeatability/reproducibility assessment and a thorough parameter stability investigation. In this approach, printing failures (and scrap) can be avoided, and physical mechanical testing will only be needed for validation of the simulation results.
The predictions from the process simulations will then be coupled with the data generated with the real-time process monitoring tools (e.g. digital imaging and optical tomography), and the post-production quality assurance methods (e.g. 3D scanning and X-ray CT scans). In essence, data from each step of the manufacturing process will be collected and analysed, and a digital thread along the whole value chain will be created. Ultimately, the qualification process for manufacturing of parts with thin walls and narrow channels can be significantly accelerated.
The project consortium constructs 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 are present and will set the process requirements. In addition, the team benefits 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) will support the project. The industrial team will work closely with RISE IVF (i.e. a research institute) and Chalmers University of Technology. RISE and Chalmers will provide 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 has access to all equipment, know-how and competence needed to carry-out this project successfully.