Ingolstadt: 2,000 new Audi's per day....
The attached photo was taken in the courtyard of the Castle in the center of Ingolstadt. Photography is not permitted on Audi's nearby business premises. For those interested; the attached link will take you to an Audi webpage where you can take a virtual tour through the various process steps.
http://www.audi.com/com/brand/en/company/locations/ingolstadt.html
An Audi body is assembled from 300 to 350 pressed parts made from sheet metal (0.6 to 2.5 mm) on coil. Galvanized steel (both Sendzimir/thermal and electrolytic), high-strength steel and aluminum are used. For some components, high strength is achieved through special pressing treatment with accelerated cooling. The material is then so strong that it can only be finished with (laser) cutting operations. Which materials are used and where varies by model. For example, the A3 consists mainly of steel, while the A8 consists mainly of aluminum.
Source:
Audi Website
In the photo, gentlemen Wehlan, Eurocopter (l) and Trykoz, Knorr-Bremse
Joining techniques and adhesive applications
Audi uses all common joining techniques for sheet metal: spot welding, laser welding, clinching, fully threaded riveting and hemming, often in combination with adhesive.
The adhesive is applied to:
a) achieve more uniform stress distribution in structural bonding. This allows thinner material to be used, with simultaneously improved fatigue properties of the joint. Structural bonding is done, among other things, when joining the inner and outer sections of the car's side walls.
b) reduce vibrations, such as the rubber-like adhesive mounted stiffening edges in roof panels and hood.
c) provide an electrically insulating layer between different sheet materials to prevent stress corrosion. In fully threaded riveting, specially coated specimens are used so that the risk of stress corrosion is also reduced at the connection points.
d) seal gaps, such as for example at hemming edges. Incidentally, the body at Audi is finally finished with PVC tracks on the edges and a wax dip treatment on the underside of the vehicle.
e) make it possible to join different materials together, such as for example the windows (1K PU with moisture booster), insulation materials and many internal and external trim parts.
f) influence deformation behavior in a crash situation.
Discussion 1K or 2K Epoxy for highly rigid, structural bonding
An important development is the application of 1K Epoxy, which cures in the muffle oven at a temperature of approximately 190 degrees Celsius and is capable of absorbing small amounts of oil and grease residues from the sheet surface without adversely affecting adhesive strength. The fact that this curing only occurs at elevated temperature is also a limitation. After cooling, material stresses develop in the adhesive layer, which can deform the sheet material and/or cause dimensional deviations. A 2K Epoxy normally cures at room temperature, so these material stresses would not occur when using it. However, the adhesion of a 2K Epoxy is severely negatively affected by oils and greases on the bonding surface. This can be improved by allowing the 2K Epoxy to cure at elevated temperature. This is done by placing an oven in the assembly line. However, this reduces the positive aspect (fewer material stresses), while an additional (cost-increasing) oven step must be built into the process. Another aspect working against the use of a 2K Epoxy is that time-dependent processes in production are to be avoided as much as possible. For now, the 1K Epoxy with high oil and grease tolerance and a defined curing time remains the most logical choice. Where necessary, the consequences of material stresses are anticipated by taking this aspect into account when dimensioning and designing the sheet parts.
Adhesive Department
The adhesive department is located in the building where painting takes place. The office and laboratory section for adhesive bonding and painting are therefore in close proximity to each other. Considerable research effort is devoted to qualifying (all different) adhesive types and primer treatments. Research is also conducted into the bondability on paint layers in connection with other paint types or changes in the painting process. This knowledge is disseminated throughout the entire group from the Ingolstadt facility.
Photo left: Audi navigation system