Production of the New Audi A4 Cabriolet

The new Audi A4 Cabriolet, which will be launched this April, is being manufactured at what is to all intents and purposes a new plant: virtually all that remains of the production halls at the Rheine plant are the walls. The contents of halls measuring 30,000 square metres in area have been ripped out and the halls themselves renovated. Audi’s partner Wilhelm Karmann GmbH produces the third member of the A4 model family for Audi at its plant in Rheine, which employs a workforce of around 1,500. Rüdiger Burda, responsible at Audi for the project coordination of A4 Cabriolet production: “The plant was essentially built in accordance with the Audi Production System.” Over EUR 100 million were invested in state-of-the-art production facilities alone.

Audi took the decision to have the A4 Cabriolet built at Karmann at the beginning of 1999. Burda: “There was one main reason for this decision: a maximum of 105 of the new A4 Cabriolet will be built daily. Such a high volume can only be partly integrated into the production structures of a large plant such as Ingolstadt. Not only that, but due to the different production methods used, it would not have been possible to produce the A4 Cabriolet on the same line as the A4 Saloon and the A4 Avant. We would therefore have had to invest an enormous amount in the plant infrastructure.”

Audi therefore chose Karmann as its production partner. This decision was also based on the wealth of experience that Karmann, a company rich in tradition, has in the production of convertibles. The Karmann plant in Rheine already manufactured over 12,000 of the previous Audi Cabriolet between 1997 and 2000, when it went out of production. A total of around 72,000 of this classic open-top vehicle were built and sold.

Since the development of the new A4 Cabriolet had already taken place at Karmann, all Audi and Karmann departments worked together intensively in accordance with the principle of simultaneous engineering. Production of the new A4 Cabriolet at Rheine was subject to the same criteria that apply for all other production locations used by the Audi Group. Quality control loops, test methods, vehicle acceptance, auditing and the assembly structure all comply with Audi guidelines, in accordance with the Audi strategy: “One name, one standard, worldwide”.

Yet the production of the A4 Cabriolet is slightly different. This is noticeable above all in the area of body manufacturing: while the A4 bodyshop at the Ingolstadt plant is almost fully automated, the Cabriolet body is assembled at Rheine in a semi-automatic bodyshop.

Rüdiger Burda explains the reason for this: “Compared with the A4 Saloon or the A4 Avant, the volume is not high enough for full automation. Not only that, but the body of the A4 Cabriolet has numerous additional reinforcements to achieve its very high rigidity. These struts in particular are not welded by robots, but manually.” For instance, the A4 Cabriolet has in addition high-strength reinforcing tubes in the A-post, sills with an optimised thickness and cross-section, a cross reinforcement under the rear seat bench, a double rear wall and special impact absorbers in the doors.

Employees at the bodyshop in Rheine work in three shifts. A total of 40 robots there weld and bond together the main assemblies, such as the bottom section, side sections, windscreen frame and add-on parts like the doors or soft-top compartment, in semi-automatic production cells. Each of the bodyshells, which weigh 450 kilograms and are made up of 110 welded assemblies, comprise 6250 welding points, 35 metres of bonded seams and over eleven metres of seams formed by inert arc welding. Before the individual body parts are finally assembled on the finishing line, the main assemblies pass through an inline measuring station. If measuring results are outside the very tight tolerances, countermeasures can be taken immediately while the body is still on the assembly line.

The finished bodyshells are then sorted into colour blocks and transported by truck to the paintshop in nearby Osnabrück where Karmann has erected a new and modern paintshop at which the Audi A4 Cabriolet bodies are sprayed with environmentally friendly water-based paints. There are a total of 14 different standard colours and a number of special paint finishes to choose from.

Once they have been painted and body-cavity sealant applied, the bodies are taken back to Rheine where they are stored in the body warehouse. From here they are introduced in-sequence into the assembly process. This is divided into five individual areas in three production halls. Final assembly is virtually the same as at the other Audi plants. The only major difference is the assembly of the soft top. Karmann supplies the complete hoods in three different colours from its plant in Osnabrück to the assembly lines in Rheine. Assembly work is performed in two shifts.

From the initial process stage in the bodyshop to the quality inspection of the finished vehicle, it takes five days with a cycle time of about eight minutes to produce an Audi A4 Cabriolet. Rüdiger Burda: “Audi has specified a very flexible daily capacity. Since a convertible is a very seasonal vehicle in terms of sales, the maximum capacity of 105 vehicles will not be produced every working day in Rheine. A fluctuation of 30 percent has been accounted for in production.”

The new A4 Cabriolet went into production on 14 January. By the time it is launched in April, production will be running at full capacity. And this will be necessary: although not one example of the new Audi Cabriolet has been on display in dealers’ showrooms, over 2000 orders have already been received for the “emotional spearhead” of the Audi model series.