The electrification of cars and aircraft with the aim of significantly reducing emissions and noise places increasing demands on laser processing. Welding has to be faster, more precise and more efficient. In connection with e-mobility, Lessmüller Lasertechnik’s optical coherence tomography (OCT) is at the forefront as a technology for quality assurance in order to meet the high requirements when welding components for electric drive units.
For this purpose, OCT offers precision tools in all process sequences (pre-, in-and post-process), which are indispensable, e.g. B. when assembling components for lightweight body constructions (where precise seam tracking is required) or components for motors and batteries – such as when welding copper wires, so-called hairpins, in electric drives.
Example – Welding quality assurance for hairpins
Hairpins for electric drive stators must be welded very quickly and without pores and spatter to ensure good electrical contact. OCT can be successfully implemented for fast quantitative quality assessment of the weld. In order to avoid welding errors, the quality of the welding beads on EVERY pair of hairpins is evaluated online using an OCT measuring beam that scans the surface of the opaque welding bead. In order to speed up the cycle time, scans are carried out along the contour within approx. 10 ms. Transverse or longitudinal measurements are possible. Height, shape and reflectivity of the weld bead obtained with OCT in combination with a previous height measurement provide information about the weld quality. Such real-time quantitative quality assessment cannot be achieved with camera-based quality control systems.
Hairpins quality check with three OCT –scans: top row – nearly identical OCT surface profiles on the same weld indicate good weld quality; bottom row – different shapes of OCT surface profiles on the same weld indicate poor weld quality.
The difference in height of the pair of hairpins before and after welding gives an insight into the volume of the molten metal. This together with the other measured surface profile parameters of the weld bead, are decisive factors for the weld quality of the hairpins. Weld quality is critical to proper electrical efficiency and mechanical strength.
For quality assurance when welding components of electric aircraft, continuous and very precise monitoring of the manufacturing process must be guaranteed. OCT can ensure fully controlled and autonomous operation of the processing laser.
Seam tracking on a battery cell