Exploring the inclined angle limit of fabricating unsupported rods structures by pulse hot-wire arc additive manufacturing

Low angle rod (especially 0° rod) is a common component of truss structure (such as lattice structure) but it is difficult to realize the fabrication and morphology control. Compared with the traditional manufacturing technology, wire arc additive manufacturing (WAAM) technology has a great advantage in the fabrication of large size lattice structures and truss structures. However, the fabrication of low angle rod is always a difficult problem in WAAM, and the morphology control ability of multi-angle rods of lattice structure is not clear. Therefore, in this study, the fabrication of low angle rod is the ultimate goal. In particular, 0° (horizontal) rods are fabricated by pulse hot-wire arc additive manufacturing (PHWAAM). The shape control of the rod, ranging from straight rod (90°) to low angle rod (0°∼ 45°). PHWAAM process is systematically studied. The fabrication process of the straight rod (90°) is analyzed and optimized in order to guide the fabrication of the low angle rod. Heat input, frequency and layer thickness are found to be three dominated factors in the fabrication process. The corresponding kinetics of molten pool, and the evolution of surface defects are disclosed, to understand the structure collapse mechanism of the 0° rod. Based on these insights, a truss structure (composed of 0° rods), a composite structure sample and a lattice structure are successfully fabricated by the PHWAAM optimized process.