An experimental study of combined spiral-elliptical scanning trajectories for blue laser welding of copper hairpin wires in electric motor stators

Blue laser welding at a wavelength of 450 nm overcomes the limited infrared absorptivity of copper but still requires a suitable scanning trajectory to compensate for hairpin assembly misalignment. This study experimentally evaluates a combined Spiral–Elliptical scanning strategy for blue laser welding of Cu-ETP copper hairpins with a cross-section of 2.0 × 2.2 mm across twelve conditions of laser power ranging from 600 to 760 W and scanning speed ranging from 25 to 35 mm/s. The results show that penetration depth, rather than weld width, governs weld quality: the weld width remains stable at 4.3 to 4.9 mm, while the penetration depth increases with power, and the welds meet both quality criteria only at 680 W. Four samples welded at 680 W achieved failure loads of 323 to 450 N and contact resistances of 30 to 60 µΩ, with elliptical scanning speed governing the trade-off between tensile strength and contact resistance.