Manufacturing the new Audi A8

Press Release

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This is brought about among other things by innovative manufacturing processes. There is thus a combination, for example, of the conventional laser and arc welding process in the laser beam-MIG-hybrid welding process (MIG stands for Metal Inert Gas) which is completely new in vehicle construction with aluminum. "We achieve diverse synergy effects by combining both joining processes. We are thus extending the limits of current thermal joining processes with regard to productivity, efficiency, seam quality and process reliability,” points out Stephan Helten, responsible for laser beam technology in the Aluminum Centre in Neckarsulm and very much involved in the development of the hybrid welding process for Audi's new top model. A welding seam length of 4.5 metres is thus achieved per vehicle. The laser-MIG-hybrid welding is used in the area of the lateral roof frame, which is fitted with various functional panels. As well as the amount of hybrid welding seam, there are also 2,600 punch rivets (1,100 on the predecessor), 64 metres of MIG welding seams and 20 metres of laser welding seams on every A8 body. The greater use of punch riveting on the successor model means that 500 spot welds and 178 clinch connections that joined the body of the previous A8 together are no longer required. Another innovative joining technique is roller-type hemming. Here rollers secured to a robot arm bend the outer panel over the inner panel and create a powerful connection by the application of a hem-bonding adhesive. The add-on components on the new A8 (doors, bonnet and tailgate) and the connection of the wheel arch with the side-panel frame are processed in this way. Inductive gelling is also a production first. In this process, the hem-bonding zones on the add-on components are heated through targeted induction (electric field) that hardens the hem-bonding adhesive. The component is thus stabilised and any slipping of the outer panel to the inner panel is avoided. The dimensional accuracy is monitored at 14 stations during the production process by the inline measuring concept using laser measuring sensors. A laser beam from a pre-defined position is projected on to a point on the component. The distance to the laser head and thus the dimension of the component is defined through the reflection of the beam. Any deviations can thus be recognised and resolved immediately. A single-piece side-panel frame in aluminum is installed on the new A8 for the first time in the large vehicle class. The over 3.45-meter long frame weighs less than seven kilograms. The side panel still consisted of eight parts on the previous model. This single-piece aluminum frame has been in volume production at Audi since the year 2000 on the A2. This is also pioneering work in vehicle construction with the alloy. above photo caption:
The use of robots in the production of the new Audi A8: the level of automation for the new top model is 80 percent