The German government stimulates automotive manufactures to produce and sale electric vehicles. Electrification of cars and aircrafts, with an aim to considerably lower emissions and noise, is placing even higher requirements on laser processing. Welding has to be faster, more precise, and more efficient. OCT, together with laser welding, is facing extensive new challenges in the e-mobility and aerospace industry, meeting the demands in welding of electric propulsion unit components. Electric vehicles and flying cars are among the greatest technological trends of the next decade.

Electric engines and batteries weight more than modern internal combustion engines, this requires other parts to be lighter to compensate for an overall acceptable weight of the vehicle by reducing the flange size or by using lighter materials. OCT allows larger tolerances in flange and gap size compared to other seam tracking techniques. Weight is also an essential factor in the aerospace industry.

The number of possible OCT applications increases with the emerging e-mobility market. Among them are welding of power storage and power train components. First attempts were made at OCT implementation for welding of hairpins in the stator of an electric motor. OCT can be successfully used for exact and fast localization of hairpins. The benefit of OCT over other inspection techniques is that it offers not only three-dimensional visualization of the hairpins but also direct real-time height measurements. The exact height of each pin is crucial for the adjustment of the focus and power density of the processing beam since welding of copper requires minimized heat input.

Demonstration of OCT application for the pre-process control of hairpins: a) Photo of the hairpins before welding; b) OCT scanning trajectory; c) OCT image serving for detection of vertical hairpins’ misalignment, shape and gap position;  d) OCT image showing lateral misalignment in a hairpin couple.

 

Copper wires (hairpins) for electric drive stators must be welded very rapidly. The processing laser beam must meet the hairpin’s surface in its focus. For this purpose, OCT rapidly scans along several lines, identifying gap locations between the pins and the pins’ misalignment to each other. The exact height of each pin, which is crucial for the adjustment of the focus and power of the processing beam, is not a problem for the height-sensing OCT system. The overall measurement time is approximately 10 ms.

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