The rapidly growing e-mobility market requires precisely welded functional components. Laser welding, together with precision sensing systems like OCT, makes a great contribution to the development of vehicles powered by electric batteries — the joining of components for body-in-white lightweight designs,  where precise seam tracking is required, or components for the motors and batteries. Welding of e-powertrain hairpins is one of them.

Copper wires (hairpins) for electric drive stators must be welded very rapidly, without pores and spatters, to ensure good electrical contact. OCT can be successfully implemented for fast quantitative quality assessment of the weld bead. To avoid risk, the quality of welding beads at each hairpin couple is assessed online with the help of a measuring OCT beam scanning the surface of the opaque welding bead. To speed up the cycle time, some scans along the hairpin contour are done within approximately 10 ms each. Crosswise or alongside measurement is possible. Height, shape, and opacity of the bead, obtained with OCT, in combination with prior height

measurement, sheds light on the weld quality. Such online numerical quality expression cannot be achieved using camera-based quality-control systems.

Hairpins’ quality inspection with three OCT scans: upper line -nearly identical OCT surface profiles on the same weld bead indicating premium quality weld; bottom line - different shapes of the OCT surface profiles on the same weld bead revealing poor weld quality.

 

The height difference of the hairpin couple before and after welding gives an insight into the volume of molten metal. This together with the other measured surface profile parameters of the bond are determining factors for the hairpins weld quality essential to ensure proper electrical efficiency and mechanical strength.

In the case of quality assurance during welding of electro aircraft components, continuous and extremely close monitoring of the manufacturing process must be guaranteed. OCT can ensure a fully controlled and autonomous operation of the processing laser.

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