Audi is expanding its leading role in lightweight design even further with the Audi R8 sports car. The new model with its multi-material bodyshells, leave the production facilities close to Neckarsulm.
Bodyshell manufacturing for the new Audi R8 is a very special low-volume production operation. The facility at Audi Böllinger Höfe close to Neckarsulm, opened in fall 2014, is set up for small production runs and broad diversity – and for high-end expertise in lightweight engineering. The high-performance sports car’s multi-material Audi Space Frame (ASF) weighs just 200 kilograms, yet is extremely stiff and impact safe. It is made 70 percent from aluminum and 13 percent from carbon-fiber reinforced plastic (CFRP) – in accordance with the Audi motto “The right material in the right amounts in the right place.”
“At full capacity, we will produce 40 bodyshells per day in two-shift operation,” explains Jochen Wagner, Head of Production Quattro GmbH. “We have divided bodyshell production into two main areas – Bodyshell Production 1 is for the aluminum elements, and Bodyshell Production 2 is for adding the CFRP parts. In Bodyshell Production 1, we also differentiate between the zone for welding work and the area for bolt-on parts and finish. The flexibility we gain through this helps us when it comes to building derivatives such as the R8 LMS GT3 race car.
The bodyshell of the new Audi R8 is created in a production rhythm of about 30 minutes, with people and robots alternating tasks. In the first step, specialists weld together the front end of the car, the central floor and the rear end from aluminum castings and extruded profile. They then connect the three modules to create the substructure. Robots handle the cold jointing processes – the complete ASF consists of 270 semi-hollow punch rivets, 270 blind rivets, 241 metric and 270 self-tapping screws; the welded seams are a good 89 meters long.
The bodyshell grows further with the greenhouse and the roof. In a cell, a five-axis machine precision cuts the connecting points for the CFRP components, the suspension and the steering to within hundredths of a millimeter. Inline laser measuring equipment checks the dimensional accuracy of the ASF. At a geometry station, technicians attach doors, lids, fenders and side parts – made from aluminum – with the aid of precision-guided fixtures.
Once the bodyshell has been through the Finish area – the final station in Bodyshell Production 1 – it is driven on a truck to the Paint Shop at the Neckarsulm plant. After cathodic dip coating, it cures in an oven at 200 degrees Celsius, where the aluminum alloys reach their final strength. “The CFRP parts are still missing at this point, because, unlike aluminum, they wouldn’t expand,” explains Jochen Wagner. “We don’t assemble them until the bodyshell is back here in the workshop. We do that in Bodyshell Production 2.”
The CFRP components form the high-strength spine of the bodyshell. Their structure varies substantially depending on where they are used. For the rear bulkhead’s transverse beams, for instance, where the primary function is maximum lateral strength, the layers of webbing are laid largely unidirectionally. Up to 14 of them are arranged one on top of the other in a layer five millimeters thick.
People and machines work closely together when it comes to fitting the CFRP parts. Robots apply finely measured quantities of structural adhesive and carry out precise jointing procedures. One of them inserts the rear bulkhead into the ASF, for which it is turned around its longitudinal axis; another positions the center tunnel on a carrier, onto which the bodyshell is then lowered. The employees of quattro GmbH install what is known as the integral B-pillar and its outer shell, then carry out the fastening and riveting processes
At the sealant station, robots apply sealing compound to all those areas where CFRP and aluminum parts meet in order to prevent contact corrosion. Finally, the bodyshell is put through another oven, this time at 80 degrees Celsius, where the adhesive and sealant cure. The new R8’s ASF is now finished – 200 kilograms of concentrated hi-tech. Audi lightweight design to a new level of perfection.
Fuel consumption of the models named above:
Audi R8 Coupé V10 plus 5.2 TFSI quattro (449 kW): Combined fuel consuption in l/100 km: 12,3** (19.1 US mpg); Combined CO2-emissions in q/km: 287** (461.9 g/mi)
Audi R8 Coupé V10 5.2 TFSI quattro (397 kW): Combined fuel consuption in l/100 km: 11,4** (20.6 US mpg); Combined CO2-emissions in q/km: 272** (437.7 g/mi)
** Fuel consumption and CO2 emissions data as well as the efficiency classes are dependent on the choice of wheels and tyres.
Further information about the official fuel consumption figures and official, specific CO2 emissions of new passenger cars can be found in the “Guide to fuel consumption, CO2 emissions and electricity consumption of new cars,” which is available free of charge from all sales outlets and from DAT (Deutsche Automobil Treuhand GmbH), Hellmuth-Hirth-Strasse 1, 73760 Ostfildern-Scharnhausen, Germany (http://www.dat.de).