Design of optimal truss components for fabrication via multi-axis additive manufacturing

Additive manufacturing (AM) has developed rapidly in recent years and has the potential to enable fabrication of structurally optimized components that have hitherto been impossible to manufacture. When the degree of design freedom is high it can be observed that structurally optimized components are often truss-like in form, such that truss topology (or 'layout') optimization methods can be used to rapidly and directly identify optimal forms. However, these forms are often geometrically complex, and the presence of overhanging elements means that they generally need to be manufactured with support structures when traditional 3-axis AM machines are employed. To reduce, or even completely eliminate, the need for support structures, multi-axis AM machines with 5 or more axes can instead be used. In this contribution a novel process-aware truss layout optimization strategy tailored for multi-axis AM machines is proposed, which involves combining curved printing surface identification with truss layout and geometry optimization. Due to the non-linear and non-convex nature of the resulting optimization formulation, two strategies are proposed: (i) performance-based, to obtain highly materially-efficient structures, though which have as little need for support structures as possible; (ii) printability-based, to obtain fully self-supportable structures, though which consume as little material as possible. Several examples are presented to demonstrate the effectiveness of the proposed approach. It is shown that fully self-supporting optimized structures can often be identified, with little or no sacrifice in terms of structural performance.