<p>Inter-bead underfill is a prevalent defect in aluminum alloy wire-arc directed energy deposition, caused by high surface tension and rapid solidification. This study establishes a circular-arc bead geometry model that distinguishes the nominal bead width (<i>w</i>) from the effective fusion width (<i>w</i>′), revealing the intrinsic limitation of conventional flat-top overlap criteria in compensating underfill in aluminum deposition. To address this issue, a torch-orientation-based overlapping strategy is proposed, in which the torch is inclined by a small angle (<i>θ</i>) during second-bead deposition while maintaining the nominal overlap distance. Experiments conducted with inclination angles ranging from 0° to 20° demonstrate that moderate inclination (<i>θ</i> = 4°–6°) effectively redirects molten metal flow into the inter-bead gap, eliminating underfill defects and enhancing metallurgical bonding. Consequently, the overlap width decreases from 12 to 10.5&#xa0;mm, corresponding to a reduction of approximately 12.5%, while the bead height increases from 4.4 to 5.1&#xa0;mm, representing an improvement of about 16% due to mass redistribution. Excessive inclination (&gt; 10°) induces melt overflow and degrades dimensional accuracy. This simple and robust strategy provides an effective process control approach for achieving dense, defect-free multi-bead overlapping in aluminum alloy wire-arc DED.</p>