Unpleasant yet necessary: Heat straightening of thin sheet metal in railway vehicle construction

Did you ever weld something onto a thin sheet metal? Within the moment, there are fascinating shapes evolving, when the sheet metal distorts in all directions. If it is a welding seam all around a square field of sheet metal, there will be bulging up and down involved, and that state can even be bistable, when you can make a bulge jump the other way just pressing with your finger. Further down the production chain towards a ready-to-use product, you have to straighten this, to “tense“ it, to be more precise. Sounds very complicated. The research visit for this report brought us to the maintenance works of the Swiss Federal Railway (SBB) in Bellinzona, in the picturesque surroundings of the Ticino valley.