Directed energy deposition-arc of thin-walled aerobat shell with structures of internal ribs and overhanging gaps

Abstract

The thin-walled aerobat shell has the common characteristic structures of staggered internal ribs and curved overhanging gaps, which are prone to the unstable flow of the molten pool during directed energy deposition-arc (DED-Arc), causing a significant decline in the forming accuracy of the components. To avoid this, DED-Arc strategies and process technologies for the characteristic structures were investigated. For the internal circumferential transverse ribs, the deflection deposition process was adopted to transform the molten pool from an overhanging state to a horizontal state to avoid the unstable flow, and a model of the depositional path point set was established based on aerobat shell feature points to ensure the forming accuracy. For internal longitudinal ribs extending in the direction of the inner-wall generatrix, a new hybrid path planning method was proposed, in which the rib contour was deposited first, followed by continuous filling via chamfering scanning or a single pass. This approach avoids the generation of protrusions and depressions when filling longitudinal ribs with irregular cross-section and improves the depositional flatness. For curved overhanging gaps, a novel process method of deflection deposition with a separation path was established. The partial separation path was deposited point by point at the boundary of gaps by adjusting the component deflection angle, which effectively inhibited the molten pool’s unstable flow and avoided deposition collapse. Ultimately, an aluminum-alloy aerobat shell was manufactured through DED-Arc using the established process technologies. The average overall size deviation was about ± 0.8 mm, and the average horizontal and vertical ultimate tensile strengths were 323.9 and 309.3 MPa, respectively, which met the component delivery requirements.