Aluminium fixtures hold Audi A2 bodies for checks

Audi relies on flexibility for measuring fixtures by using Alufix fixtures to suport and clamp Audi A2 body-in-white during measuring procedures.

Audi relies on flexibility for measuring fixtures by using Alufix fixtures to suport and clamp Audi A2 body-in-white during measuring procedures.

Audi AG has brought the first premium class automobile with a complete aluminium body onto the market, the A8.

But not only in manufacturing of car bodies like the new A2 is aluminium racing ahead.

This material is also being used in quality control in the form of a fixturing system.

The new Audi measuring centre in Neckarsulm is impressive.

The Audi A2, which has been on the market since June 2000, undergoes through technical and measuring procedures from pre-series through to series production there.

The equipment, in extremely modern measuring areas, comprises of 2 Zeiss 3D horizontal (arm) measuring machines and Witte Alufix fixtures for holding body parts during measuring.

The measure of flexibility was decisive as far as choosing a fixturing system was concerned: "The possibility to undertake changes at any time on finished fixtures is extremely important for us," said Dipl.-Ing Thomas Junghanns, manager of Quality Control Body Shop A2, when underlining the use of Alufix.

The automobile manufacturer looked back on previous good experience with the modular fixturing system, so using it in Neckarsulm seemed the obvious choice.

Experience has shown that only during the actual fixation of the workpiece, stability or instability of a workpiece and therefore the need for additional support becomes apparent.

There must be a possibility to carry out immediate changes or extend with further adaptations.

The modular basic concept of the Alufix system allows users freedom of flexibility, which caters for situations or changes in planning.

The system made of high-tensile aluminium comprises of more than 1500 single components, which can be assembled individually for any application.

For complicated designs there is a parts library, Fixmes, as well as Alufix-Expert software available.

The fixtures can be disassembled after use and single elements can be used for new projects.

In the measuring room at Neckarsulm a match metal fixture for holding and measuring the A2 floor sheet metal parts as well as several sandwich plates for sidepanels are in operation.

The match metal fixture for measuring the floor parts of the A2 constitutes a complicated looking structure.

It was built on the basis of the data control model, which portrays the result of the car designer in a ration of 1:1.

The technical data of the approved control model is the pre-requisite for the following analysis measurements for fine adjustment parts and assembly groups which follow.

This master cube accompanied the A2 floor from the pre-series to series production.

All parts within the floor group are analysed on this fixture regarding their position and fit to one another.

The match metal fixture in the A2 measuring room comprises of three fixture segments for holding separate floor parts.

Each sheet metal floor part is held on a separate Alufix fixture.

Other fixtures, that is, for cowl and wheelhouses are added.

The single fixture segments are mounted on to horizontal sandwich plates.

For actual mounting on to the master cube the sandwich plates are separated.

The fixtures for cowl and wheelhouses are on the same sandwich plate as the front floor.

The middle part holds the floorpan.

The rear wheelhouse is mounted as part of the rear car.

After the workpieces for front, middle and rear car parts have been mounted on to the fixtures, measuring of the single parts/fixtures takes place.

After that the sandwich plates are moved together over a distance of approx.

25mm on a smooth-running linear guide.

Requirements regarding flexibility and stability were high on this master cubing.

In order to carry out short-term changes and to be able to use the fixtures for future models, flexibility was in the foreground for the Audi users.

Not least for economic reasons they chose a system, which offers the possibility to hold several parts using only one fixture.

Sandwich plate is used for fixing side panels and doors.

Sandwich plates are mostly used vertically for fixing body parts in car line.

In Audi's Neckarsulm measuring room three vertical sandwich plates are holding A2 sidepanels and doors.

The rigid, anodized sandwich plates are characterized by lightweight and high stability, whereby they are especially suitable as a base for large measuring fixtures.

The standard size of sandwich plates corresponds to European pallet format 1200x800x150mm.

They are made of aluminium surface plates and a sandwich middle in the form of alu pipes.

A continuous grid allows connection with workpiece adaptations.

The vertical sandwich plates used here are equipped with a special quick connecting system developed by Audi.

This system, together with a vertical or horizontal scale, allows fast positioning of supports for different workpieces.

Because of the possibility to exchange supports quickly, a sandwich plate can be re-equipped for several workpieces in a short time.

Audi's measuring technicians underline the fast exchange possibility of supports.

" Several workpiece changeovers take place every day.

The measuring cycles stipulated in quality planning require this flexibility, further it must be possible to change quickly when quality problems arise", says Dipl.-Ing Thomas Junghanns.

The possibility to hold unknown parts and make changes at any time is also emphasized.

As the plates are extendable, that is several plates can be joined together, they can be used for different applications, i.e for very large workpieces, as a basis for cubings (see above).

In order to do this the sandwich plates are connected on the face ends using special couplings.

Using similar materials for workpiece and fixture is an invaluable plus.

That the workpiece and fixture are both in aluminium means that slight temperature changes are less noticeable because of the same temperature expansion coefficient.

This aspect becomes especially obvious during projects with large surface areas.

The best results for the A2 aluminium body were achieved using aluminium fixtures.

The high degree of flexibility, which allows changes to finished fixtures, is also a recommendation for using the Alufix system at Audi.

In addition there is the possiblilty to use master cubings and sandwich plates for future models and totally different workpieces.

This aspect renders a considerable contribution towards fast achievement of quality goals and reduction of quality costs.

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