Safer and less expensive cars
The automobile assembly process relies heavily on welding to join two components together. Current techniques for quality and safety control of laser welds rely largely on offline inspection, meaning that the part is completed and removed from the production line in order to be tested. Thus, inspection incurs additional operational costs that are then incorporated into final product cost. Perhaps more importantly, regarding safety, current inspection and tear-down by putting a finished car through a crash test means that only samples of all parts produced are actually tested. The ‘Development and validation of on line monitoring and NDT inspection of laser welded thin sheet automotive components’ (Oliwam) project was designed to minimise the safety and financial costs incurred by offline weld testing. Specifically, the researchers set out to develop a new fully automated online monitoring and non-destructive testing (NDT) inspection system enabling 100 % inspection rates for laser-welded thin sheet automotive parts. The system was designed to produce real-time evaluation of results and immediate remedial actions to further reduce repair costs and scrap rates. The research consortium chose two automotive applications for prototyping the Oliwam system: a tailor-welded blank (TWB) that is part of the Seat 3-door frame and a body-in-white (BiW) assembly that is part of a VW door inner. For both applications, the investigators selected the five most critical imperfections typically encountered and determined their acceptance levels in terms of imperfection pass/fail. The Oliwam system successfully detected lack of fusion in the TWB joint application. In addition, the system successfully detected the most critical of imperfections in the BiW joint application, namely lack of fusion at the second interface, which until now was very difficult, labour intensive and costly to detect. In summary, implementation of the Oliwam system should provide fully automated online inspection of 100 % of laser-welded automotive parts. This promises to significantly reduce manufacturing costs and safety hazards and thus increase the competitiveness of the European automotive industry.
