The production of seats exemplified.

In the development of the new 7 Series model it was a matter of concern that the driver and the passengers feel well and enjoy the individual and luxurious comfort the car offers. That is why we developed all-new seats that perfectly adjust to the individual seating requirements. In their complexity the electrically adjustable multifunction comfort seats rank unique in the market due to the vast number of adjusting possibilities and additional equipment such as the infinitely electrically adjustable backrest width of the front seats or the multivariable adjustable rear seats.

A driver or passenger seat can be compared to a good piece of clothing: It must be very well finished, suit well, fit perfectly and must neither pinch nor scratch. Due to in-house development and production it was possible to exclusively produce the 7 Series model’s seats featuring innovative elements in accordance with the customer requests and to follow the aim of "offering maximum comfort at maximum functionality". Thanks to pathbreaking production methods and the BMW specialists’ long-standing know-how these comfortable seats with their different production variants currently amounting to 6,000 became a reality. The use of virtual tools helped at an early stage to considerably reduce by up to 30 percent the time needed for the development of features such as seat covers through the quick and accurate creation of prototypes. Production methods have been redeveloped and innovative technologies have been used to pay tribute to the demands of flexibility, a wide range of options, sustained production and, last but not least, profitability.

The vast array of high-tech features of the new 7 Series model’s seats, whose full equipment includes up to 34 electromotors and 6 electronic control units, made necessary the integration of new methods of testing. The electrically adjustable backrest width, a feature never seen before in automobile construction, and the climate seat featuring active ventilation, could only be realized through the use of revolutionary sewing methods and innovative materials (climate-controlled leather).

At the BMW Plant in Dingolfing around 700 employees are currently working on the production of seats, being responsible for the manufacture of complete seats for 5 and 7 Series cars as well as for sewing high-quality leather for small-lot and individual production.

Robots perform three-dimensional sewing operations – an industry first.

Three-dimensional sewing operations made possible by state-of-theart control technology has become a reality. A robot-controlled sewing system, a BMW in-house development, produces the components for the 7 Series model’s exclusive leather upholstery.

When the BMW product and process engineers designed the system they were, for example, initially faced with the apparently easy task of joining the varicoloured threads necessary for the different leather colours to a filament yarn that automatically goes through a needle’s eye in case of a colour change. It was not possible to simply knot the two ends of the threads together in case of a colour change as even the world’s smallest knot does not go through a needle’s eye that is only 0.5–0.7 mm wide. Another method had to be found to tie the threads together. The answer was "splicing", which is a method and a technical term better known from sailing. What does "splicing" mean in this respect? In an air chamber the ends of the threads are disentangled into individual threads and twisted together at the same time. The spliced joint has a tensile strength of about 90 percent, which is enough for the old thread to pull the new thread through the needle’s eye, the advantage being that the spliced joint is not thicker than the thread itself, which allows an all-automatic change of colours.

The method of "splicing" forms an important yet small part of the complex robotized sewing system that was launched in the middle of 2001.

The system is a closed, square conveyor system that is masterminded by two interbus systems. It is currently made up of six and in future of eight workpiece carriers, two all-automatic colour yarn changers for 15 colours, a colour recognition sensor and pleating tool, three docking stations that connect the travelling workpiece carriers with the bus lines and a robot, which is the actual highlight, that, in addition to two- and three-dimensional sewing operations, is responsible for changing the upper thread and the under-thread in case of a colour change.

The following is to give you an example of the sewing operations that have to be performed on the centre section of the BMW 7 Series model’s backrest’s rear side: The required leather components are put on the appropriate workpiece carrier – three leather pieces are placed in the middle and two leather strips respectively to the left and to the right of them. The colour of the leather is determined by means of sensors. The respective information is transmitted to the workpiece carrier’s data storage medium, the former advancing to and stopping at the first docking station. The data are read out from the storage medium, evaluated and passed on. The changer of the upper- and under-thread is told which colour is to be used. The pleating tool receives information on the position of the transverse seams and the robot is told which program must be selected for two-dimensional and three-dimensional seams.

Then the actual production process starts. In case of a colour change a transport slide takes the bobbin out of the magazine. After that, the old bobbin is replaced by the new one by a robot. A grappler grips the upperthread spool and takes it out of the changer system equipped with 16 different colour variants and threads the yarn through the needle eye of the sewing arm. The following commands are received by the workpiece carrier via the bus system: Raise middle part, press side parts to the middle parts, sew transverse seams. After that, the middle piece is stretched by means of air intake in order to ensure precise longitudinal seams (three-dimensional seams). The enormous advantage of this high-precision system lies in its flexibility and high degree of automation, allowing the processing of different pieces of leather and the repositioning of seams. The system can even be used for the processing of other parts. A second robot that will be responsible for the production of the front and rear seats of other models is planned to be commissioned in 2003.

Pathbreaking technology:

The use of the vacuum foaming method in the production of seats. Back in 1995 the BMW Plant in Dingolfing launched the conventional production of foam parts for front seats, rear seats and center armrests. Three years later the vacuum foaming technology was developed within the company, which was further advanced since then and finally made ready for use in series production. With this technology the engineers achieved a weight reduction by 20 percent while maintaining the quality standard and realizing a high level of fatigue strength and superior comfort at the same time. A further effect of this technology is a reduction of costs exceeding 1 million Euros each year as less material is needed.

Hidden perfection: the reaction process.

Innovation: Vacuum hardening process.

During the conventional non-vacuum hardening process millions of foam cells "battle with" the atmospheric pressure when rising up within the tool and are thus prevented from adopting their ideal form. Due to the pressure exerted on them the cell structure becomes more compact and therefore heavier.

During the new production process the tool’s top side and bottom side are tightly pressed together by air cushions after the mould carrier has been closed. The air in the tool is sucked out at the annular gap via a closed-circuit pipeline. Thanks to the vacuum state the foam develops an ideal cell structure, even though 20 percent less material is used in the process. During the hardening process the vacuum is removed, the tool is automatically opened and the finished foam part is taken out of the tool. To open the cell walls that are still closed and to make the seat component elastic, the former is subsequently processed by a vacuum press. Finally, the component is made available to the upholsterers after it has cooled down and undergone examination.

The new vacuum process is consistent with the environment and complies with the high BMW safety and quality standards. At the moment the technology is exclusively used at the Dingolfing Plant. Plans to extend it to the Munich Plant’s production are currently being examined.

Camera-controlled industrial robots assemble vendor parts.

A myriad of different components such as the seat’s and backrest’s frame structure, belt tensioners or panels contribute to the perfection of the finished seat. Whilst in the past these components were manually assembled, this job was taken over by two camera-controlled industrial robots when the production of the new 7 Series model was taken up in 2001. One of the robots is responsible for riveting panels on the seat frame while the other is in charge of bolting on the components which make up the seat’s and the backrest’s frame as well as the belt tensioners.

Simulation technology reduces development time.

The computer program Wrapstyler used in the production of seats is the first and only application within the BMW Group to enable at an early stage of development the fast production of a prototype on the basis of a three-dimensional CAD model and two-dimensional profiles. The seat covers and the foam parts are designed simultaneously. Time-consuming co-ordination processes are avoided. State-of-the-art cutter technology for cutting the materials of the covers is used in these processes, thus complementing the constant virtual description of the entire seat.

Perfect interaction between man and technology.

Despite most progressive technologies and methods the employees will always play a vital role in successful production. It is them who effectively use the tools and facilities, check them for correct operation, constantly improve them and develop and finally realize progressive conceptions.