The efficiency of a centrifugal pump for mechanical pump fluid loops, apart from the design, relies on the performance of the closed impeller which is linked to the manufacturing process in terms of dimensional accuracy and the surface quality. Therefore, the activities of this paper were focused on defining the manufacturing process of a closed impeller using the additive manufacturing technology for mechanically pumped fluid loop (MPFL) systems in space applications. Different building orientations were studied to fabricate three closed impellers using selective laser melting technology and were subjected to dimensional accuracy and surface quality evaluations in order to identify the optimal building orientation. The material used for the closed impeller is Inconel 625. The results showed that both geometrical stability and roughness were improved as the building orientation increased, however, the blade thickness presented small deviations, close to imposed values. Finishing processes for inaccessible areas presented significant results in terms of roughness, nevertheless, the process can be further improved. Abrasive flow machining (AFM) post-processing operations have been considered and the results show major improvements in surface quality. Thus, important steps were made towards the development of complex structural components, consequently increasing the technological readiness level of the additive manufacturing process for space applications.
In the space industry, the market demand for high-pressure mechanically pumped fluid loop (MPFL) systems has increased the interest for integrating advanced technologies in the manufacturing process of critical components with complex geometries. The conventional manufacturing process of a closed impeller encounters different technical challenges, but using additive manufacturing (AM) technology, the small component is printed, fulfilling the quality requirements. This paper presents the Laser Powder Bed Fusion (LPBF) process of a closed impeller designed for a centrifugal pump integrated in an MPFL system with the objective of defining a complete manufacturing process. A set of three closed impellers was manufactured, and each closed impeller was subjected to dimensional accuracy analysis, before and after applying an iterative finishing process for the internal surface area. One of the impellers was validated through non-destructive testing (NDT) activities, and finally, a preliminary balancing was performed for the G2.5 class. The process setup (building orientation and support structure) defined in the current study for a pre-existing geometry of the closed impeller takes full advantages of LPBF technology and represents an important step in the development of complex structural components, increasing the technological readiness level of the AM process for space applications.
The main objective of this study was to investigate thermoplastic materials design and fabrication processes for manufacturing composite impeller blades. Polyurethane (Necuron) and ABS (3D printed) thermoplastics were chosen due to their good mechanical properties, tooling applications, easy manufacturing and lifetime. For both thermoplastics, workability and hardness tests were performed, as well as microstructural and mechanical characterization evaluating their physical and mechanical properties. A 1:2.5 scale mould was designed and milled from Necuron N651 and N1001 and used for manufacturing of 1:2.5 scale composite impeller blades. Also, 1:1 scale ABS mould components were 3D printed and used to manufacture full scale composite impeller blades. All composite impeller presented good surface quality and tolerances with respect to CAD design, thus answering to requirements related to composite processing
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