Relation of surface texture and surface finishing with design of additive manufacturing for aerospace applications

Metal additive manufacturing (AM) techniques and design for additive manufacturing (DfAM) enable fabrication of light-weight, complex and/or intricate geometries, with superior mechanical properties. However, the surface texture of an as-built AM part is extremely uneven when compared to parts manufactured with conventional methods. For example, the average roughness of an as-built part can range from 5µm to 40µm for powder bed AM techniques. Depending on the requirements of the end-use application - whether to increase fatigue strength by eliminating stress concentration points or to smooth surfaces to allows for consistent surface area for fluid flow, and/or cosmetic appearance - these surfaces must be subjected to post-built surface finishing. While hybrid surface finishing methods, developed especially for AM, enable efficient finishing with minimum material loss, they can be limited at geometrically complex and intricate edges. Additionally, inspection of the surface texture at various stages from build to end-use is challenging for complex geometries. This begs the question as to whether prior knowledge of geometric limitations of finishing and inspection can be implemented into the design to leverage improved timelines, cost and sustainability. This discussion will explore the various contributing factors and the current state of the relation between design and surface texture post fabrication.