Comprehensive benchmarking of laser welding technologies including novel beam shapes and wavelengths for e-drive copper hairpins

Abstract

Laser welding is the industrially accepted method for the joining of Cu hairpin windings in the production of electric drives. High brilliance laser beams are scanned over the bare ends of the Cu wires producing a rapid connection through deep penetration remote welding. Despite being an accepted manufacturing method, laser welding of Cu hairpins still requires detailed studies concerning manufacturing productivity and quality. As the availability of novel laser sources with higher power levels, new wavelengths, and beam shaping capabilities increase, the need for benchmarking studies emerges. In this work, six different laser welding systems were compared in terms of process productivity and quality during the welding of Cu hairpins used for automotive traction. The different solutions presented power levels from 3 to 6 kW, with wavelengths from near infrared (NIR) to visible, including in source dynamic beam shaping. The weld bead formation was observed through high-speed imaging. The welds were analyzed in terms of their geometry, internal defects, and most relevantly for their mechanical strength. The results showed advantages of each of the employed system while the laser systems providing the highest irradiance profile produced the fastest weld with more elevated mechanical strength independently from the wavelength.