Aluminium and steel are joined both mechanically and by bonding

The A8 flagship makes extensive use of the ASF concept, saving weight substantially

Since Audi opened its Aluminium Centre in 1994, thus concentrating its experience in lightweight design and the expertise of the Development, Production Planning and Quality Assurance departments, the innovative body design concepts from the Neckarsulm factory in Germany have been instrumental to the success of the brand.

1994 was also the year the first Audi A8 left the production line ? the first vehicle built on the basis of the Audi Space Frame (ASF) concept ? a high-strength aluminium frame structure whose supporting structure is made of extruded aluminium sections and die castings. Aluminium sheet panels form a positive connection and perform a load-bearing role within this structure. The components of the ASF space frame vary in shape and cross-section depending on their function ? like the bones of the human skeleton, they are made to fulfill their task as well as possible, while having the minimum possible weight.

This new design also called for new production technologies. Improved light alloys and process techniques were thus developed by the specialists in Neckarsulm. Along with welding and bonding, punch-riveting was incorporated for the first time into joining techniques in the car manufacturing process.

The A2 model, the first high-volume car to feature ASF technology, followed the A8 in 1999; more than 176,000 units of this car were produced, of which 6,450 were Audi A2 1.2 TDI models with an incredible fuel consumption rate of?33.4 kms/litre (94.5 mpg).

The bodies of the new TT? and R8 were also developed at the plant in Neckarsulm and the Lamborghini Gallardo and the Gallardo Spyder also have their roots here. More than 378,000 vehicles with aluminium body construction have now left Neckarsulm.

Aluminium frames for the A2

In the meantime, the development centre represents more than purely the use of aluminium alone: high-strength steels, tailored blanks, fibre-reinforced plastics and magnesium are increasingly used at Audi. This was the reason Audi renamed the centre “Aluminium and Lightweight Design Centre” (ALZ) four years ago.

?Although aluminium remains the key material in lightweight design, we are continuing to step up our efforts to investigate the potential of other materials,? explained Heinrich Timm, Head of the Aluminium and Lightweight Design Centre in Neckarsulm.

?Our goal is to exploit the potential of materials for lightweight vehicles as effectively as possible and thus to use the right materials in the right place. The systematic implementation of lightweight design in body manufacturing helps to achieve a noticeable reduction in fuel consumption and thus makes a significant contribution towards reducing CO2 emissions without compromising comfort, performance or safety. Reducing weight by 100 kilogrammes saves 0.3 litres of fuel over 100 kilometres, or in other words, reduces CO2 emissions by 7.5 to 12.5 grammes per kilometre driven,? he said.

Latest TT has aluminium structure and accounts for as much as 69% of body weight

Developing lightweight bodies on the basis of intelligent hybrid construction is therefore the driving force behind the high-tech plant.? This is evidenced by the body of the new TT which represents the first of the Audi Space Frame with a hybrid construction. Aluminium and steel are joined both mechanically and by bonding. Aluminium accounts for 69% of the total body weight. Fully galvanised steel components are located at the rear of the floor panel; the doors and the luggage compartment lid are also made of steel. This provides an optimum distribution of axle loads, making for superior handling.

Assembly of the A2 at the Neckarsulm factory which has produced more than 378,000 cars with aluminium construction

Joining is performed in a variety of ways too within the scope of this technology ? by punch-riveting, clinching and bonding. A fourth joining technique has now been added to the list: self-tapping screws, developed by Audi, are inserted by robots and melt the surface of the aluminium component as a result of the friction they cause at the beginning of the screwing-in process, thus penetrating fully into the material, forming a positive connection with it.

Another innovative concept used on the new TT is the aluminium zero joint that is produced between the roof and the side section during laser-welding. ?Our many years of experience with laser technology have resulted in a further highlight being implemented ? the ?laser clean? process in the join zones. This saves us the effort of having to wash large components and render them passive,? added Timm.

These features of Vorsprung durch Technik have certainly paid off: at the end of 2006, the Automotive Circle International presented Audi the Euro Car Body Award for the new Audi TT body concept developed at the Neckarsulm plant. As far back as 2003, Audi had already received this award for the A8 Audi Space Frame body concept. The Audi TT sports coup? beat 13 renowned competitors from around the world to take the award.

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