High-quality additive manufacturing of complex thin-walled rotary parts via a variable-diameter helical path and vector-orthogonal multi-axis method

Conventional fixed-axis zigzag scanning paths in additive manufacturing (AM) of thin-walled rotational components often induce melt pool instability due to abrupt scanning speed variations, leading to geometrical inaccuracies. To address this limitation, this study proposes a multi-axis AM strategy that integrates a variable-diameter helical path with dynamic vector control. This approach enables constant-velocity deposition by constructing a first-order geometrically continuous (C 1 ) path, while simultaneously adjusting the print head orientation to ensure self-supporting and stable formation. Comparative experiments demonstrate that the new strategy significantly outperforms the conventional method, yielding remarkable improvements in dimensional accuracy (cylindrical cross-sectional deviation: 0.078 mm vs. 0.768 mm) and surface quality (Ra: 8.30 μm vs. 110.75 μm), while effectively eliminating feature loss in overhang regions. Mechanical property assessments reveal an enhanced consistency in interlayer tensile strength (with a reduced range of 47.9 %), a 62.1 % increase in microhardness, and a 0.41 % increase in the average density. This study confirms that the variable-diameter helical path with dynamic vector control is an effective and robust strategy for high-quality AM of complex thin-walled rotary parts. • A variable-diameter helical path using vector-orthogonal multi-axis AM delivers constant-velocity deposition and adaptive support, tackling molten pool instability and overhang failure. • The method delivers a 10x improvement in dimensional accuracy (0.078 mm cylindricity) with 92% lower roughness (Ra=8.30μm), 62.1% higher microhardness, and 0.41% greater density. • The curvature-clad thickness coupling mechanism is revealed, clarifying the cause of over-deposition on concave surfaces and laying a theoretical foundation for high-precision forming.