Concurrent optimization of truss structures and build directions for multi-axis additive manufacturing

Additive manufacturing (AM) has undergone rapid development over the past decade, yet printing parts with overhangs still poses a critical challenge, restricting the fabrication of components with arbitrary geometries. In structural optimization, incorporating overhang constraints can mitigate this issue. However, prior research has predominantly focused on 3-axis machines, leaving multi-axis capabilities insufficiently explored. These conventional 3-axis approaches often necessitate considerable trade-offs in structural material consumption. To overcome this, our study introduces a novel two-step optimization method tailored for multi-axis AM, which uses an optimized structure from traditional layout optimization as the starting point. The first step involves decomposing the design domain into multiple zones and solving a novel optimization problem to identify optimal local build directions for each zone, aiming to maximize the structure's printability. If the printability is still not satisfactory, we proceed to a second step, which refines the structure and build directions to minimize overhanging elements. Our examples validate the effectiveness of the proposed method, showing that the substantial performance sacrifices typically associated with 3-axis approaches are reduced to less than 7 % with our multi-axis AM-based approach.