Induction meets laser

Behind the protective doors of the laser welding station, the inductor surrounds the drive shaft without touching it. While power is flowing, nothing is visible to the naked eye. But if Zoran Bubic, responsible for process planning at GKN Driveline, were to touch the spot where tripod and tube will soon be joined by a laser beam, he would burn himself. The metal here – and only here – has reached a temperature of about 500 degrees Celsius. Mr. Bubic turns away from the manufacturing cell and explains: "The inductor provides a large amount of heat extremely quickly, to a very small volume of steel. The laser then works a welding point that has been perfectly pre-heated, resulting in ahighly reliable process."

Many successful welding processes today make use of induction, particularly in applications that call for pre-heating. The laser’s minimal heat input has a downside when it comes to deep penetration welding of high-carbon steels. The cold workpiece chills the welding seam, and this can lead to hardening and quality defects such as cracks in the zone affected by the heat. Conventionally, pre-warming has meant heating an entire component in a furnace. With the inductor, however, the heat is generated in a matter of seconds, on a very limited space. Moreover, "pre-heating takes place in the welding cell," says Zoran Bubic. "This lets us eliminate the preheating station and avoid handling hot components. What’s more, we can save quite a bit of heating energy, not to mention a lot of time.

Precise, fast, and contact-free

Even the most enthusiastic lecture on induction is likely to put a room-full of mechanical engineering students to sleep. Induction sounds a lot like high school physics and it’s everywhere — even in an IKEA cooktop. But induction’s low-tech nimbus soon dissipates when real know-how is involved. Every induction application is dedicated to a specific workpiece as a balanced system that combines an inductor and a high-frequency generator. Locally, its effect can be precisely controlled, to within one Kelvin. This controllability and the speed at which heat is generated make induction a wonder weapon of sorts. And induction really is easy to handle: induction systems can easily be integrated into manufacturing processes, interlinked automation systems, and production plant concepts.

Applications range from work at room temperatures to work at several thousand degrees Celsius. As of 200 degrees Celsius, things start to get interesting for metal processing and laser technology. Above this temperature, many non-metallic protective and functional coats evaporate. This means that the same inductor that pre-heats the weld spot can now also clean or decoat this spot — and this spot only. At temperatures exceeding 900 degrees Celsius, workpieces can be hardened or softened locally. When it comes to induction, the possibilities are just about endless.

Pearls on a string
“At first glance, using induction in laser processing isn’t always an obvious choice,” says Georg Schneider, induction sales representative, at the TRUMPF subsidiary HüTTINGER Elektronik. “But while user-programmable lasers remove the limitations of mechanical processes, the pyrometer-controlled induction systems replace conventional heating systems such as furnaces and put thermal processes exactly where they belong. In power trains, for instance, they are located directly at the welding joint.” At the same time, the inductors can be designed to handle a large number number of component variants. As a result, it no longer matters which transmission model is being welded, as Georg Schneider explains. In the hot-forming process sequence, too, induction offers more than one possibility for heating sheets prior to pressing. Locally induced heat can soften specific sections of hardened components.

The automotive industry is now IMNEAdiscovering this can be useful, bAir Max 95 20th Anniversary Flyknit