Additive manufacturing defects in polymeric lattice structures: a comprehensive analysis of morphology, distribution, and printing orientation influence

Abstract Despite the advantages of additive manufacturing technologies, such as fabricating highly complex workpieces, including lattice structures at low costs, they might result in various defects and imperfections in final products. Process-induced defects can compromise the mechanical performance of printed components. To investigate the effects of process-induced defects on the mechanical performance of lattice structures, detailed characterisation of manufacturing-induced defects is necessary. This also helps optimise the printing parameters, especially printing orientation—a key printing parameter—for obtaining structures with minimum imperfections. To achieve this, the polymeric FBCCXYZ lattice structure, comprising struts fabricated in various printing orientations, was created via the powder bed fusion process. X-ray computed tomography (CT) and custom-developed image processing techniques were employed to comprehensively analyse the structural elements, including struts and nodes, and characterise the morphology and distribution of defects. The analysis identified the presence of geometry-related defects, including under-sizing and thickness variation defects, as well as internal voids of various sizes and shapes within the struts oriented in all directions, and structural nodes. The correlation between the void geometry and powder particles and the irregular geometry of voids suggests that lack of fusion is the primary cause of void formation, with voids primarily oriented along the printing direction. The novelty of this study lies in its advanced image-processing methodology, which accurately captures the geometry, size, orientation, and distribution of internal voids in lattice structures. In addition, this approach is applicable to any lattice topology, independent of the additive manufacturing method or material.