BMW M6 - In Depth (Part II)

Press Release

Production of the BMW M6

High-Tech and Individual Style in One

The new BMW M6 is built exclusively at BMW’s Dingolfing Plant, the largest of the 22 BMW Group production plants worldwide. Here some 22,000 associates build more than 1,000 BMW 5, 6, and 7 Series a day, using the most flexible operating structures and large-scale production technology for the production of highly customised cars tailored individually to each purchaser.

Bodyshop

The body-in-white of the new BMW M6 is built on the same facilities as the body of the BMW 6 Series Coupé and the BMW 6 Series Convertible, highly flexible robots and intelligent control systems serving to assemble and complete the individual body variants one-by-one in any random order. In the process the BMW M6 benefits from innovative bonding and joining technologies used in regular production of the BMW 6 Series.

Specific components exclusive to the M6 are fitted indirectly in the production process, additional mounting points and bolts, for example, being provided on the body structure in order to take up the output of the M6’s power unit. The roof bracket made of carbon-fibre-reinforced plastic (CFP) is bonded into position manually without extending the production process or the assembly time required. This provides the foundation for the roof made of carbon, the same material used in Formula 1 and, of course, on the already legendary M3 CSL. Each kilo saved in this way has a positive effect on the car’s driving dynamics and fuel economy, at the same time raising that sheer driving pleasure so typical of BMW to an even higher level.

The body structure with its combination of steel, aluminium, and plastics also makes a significant contribution to the supreme agility offered by the new BMW M6. The low-weight aluminium front section, for example, connected directly to the steel bodyshell of the car, is made of aluminium panels, extrusion pressure profiles, internal high-pressure-moulded tubes, and aluminium castings, together with some 600 rivets and several metres of protective gas welding seams. The doors and the engine compartment lid are also made of aluminium, the front side panels come in a special thermo­plastic material, and the rear lid is made of SMC sheet moulding compound. The result is a car body which, through its ideal distribution and axle loads, enhances the dynamic features of the BMW M6 in every respect.

Paintshop: seducing your senses

The BMW M6, despite its wide range of different body materials, goes through all the usual processes in applying the paintwork. The first step is to remove grease from the body by pre-treatment in a rotation dip bath, after which the body is cleaned and covered by a layer of zinc phosphate forming the foundation for the paint layers to follow next. Then the phosphated body- shells are covered by a layer of anti-corrosive paint in the cathodic dip bath (CDP) and are dried at 180 °C. The second layer of paint, a filler already matching the subsequent topcoat, is subsequently applied by high-speed rotation sprayers. This forms the foundation for the next layer of water-based paint applied on a special paint line in order to give the car its actual body colour. In this process a highly flexible paint supply system able to work with very small quantities of paint serves to apply the four exclusive M colours as well as the overall range of approximately 250 individual colours, ensuring excellent quality throughout the entire process. After the body has been dried in an intermediate dryer at a temperature of 70 °C the clear powder paint applied in conclusion gives the surface a beautiful glossy finish and adds the right kind of protection.

The Paintshop in Dingolfing uses a number of innovative concepts for the specific combination of materials on the BMW 6 Series. Thanks to flexible production management, for example, the SMC components – such as the rear lid – can be fitted right from the start in the Bodyshop and remain on the car throughout the entire painting process. The thermoplastic side panels, in turn, are the first skin segments of the body which go through the entire process of applying the paint right from the start, thus setting off the varying degree of thermal elongation of plastics and the aluminium front section during the subsequent drying process, since automatic recognition of materials enables the topcoat dryers to adjust their temperature within a few seconds.

An efficient and highly innovative process of colour-matching measures the colours on the body work online, ensuring perfect harmony of colours on both the body and on individual add-on parts such as the bumpers, side-sills or rear-view mirrors.

Assembly: a dream becomes reality

While job processes in the Pressing Shop, at the Bodyshop, and at the Paintshop are largely automated, the human “touch” still comes first in the Assembly Area. Here, therefore, appropriate qualification and motivation of the associates working on the line provide the foundation for perfect production of customised cars of the highest quality. In their work these associates are supported by the latest technologies and particularly ergonomic job conditions: Depending on the work to be done, car bodies can be turned and swivelled to the best position for optimum access, and may also be raised and lowered as required. With associates being able to “ride along” on the production line and use hydraulic handling units for effortless transportation of heavy components such as seats, doors, or batteries, working conditions are again facilitated to the greatest possible extent.

Like all other components on the BMW 6 Series, special parts and com­ponents exclusive to the M6 – such as the engine, the seats, the steering wheel, and the rear axle – are delivered to the assembly line just in sequence. Only the roof proudly showing that it is made of reinforced carbon-fibre is bonded on to the ready-painted body of the car in a separate process prior to assembly as such. At the same time the BMW M6 comes with an extra-thin rear window helping to reduce weight to a minimum, while not in any way detracting from the car’s body stiffness, its structural safety, or its noise and temperature insulation.

Various function tests and fine-tuning routines are conducted in the last stage of assembly, the finish process, before the car is cleared for delivery to the customer.

Innovative carbon-fibre technology with proven benefits in series production

BMW builds the carbon-fibre roof of the M6 in-house, using special facilities at the Landshut Plant, where lightweight technology experts make the roof out of several layers of this expensive material first pre-moulded in a dry state, then moistened with resin in the RTM (resin transfer moulding) pro­cess, and finally finished.

BMW already featured a reinforced carbon-fibre roof for the first time in a limited edition on the M3 CSL. Now, introducing the M6, BMW has gone one step further, for the first time integrating CFP technology in the production of a larger number of models.

The front and rear bumpers are also made of CFP for the first time in a spe­cial process developed specifically for this purpose at BMW’s Landshut Plant and remaining unique the world over to this day. In this process the individual segments of CFP are woven layer-by-layer around a core, cast in resin, and subsequently hardened before the core material is removed. The result is an extremely light, but nevertheless extra-strong hollow profile substrate reducing weight by 20 per cent at the front and 40 per cent at the rear in the interest of significantly enhanced agility and handling.

The Customer-Oriented Sales and Production Process: punctual, quick, dependable

The BMW Group has set new standards with its Customer-Oriented Sales and Production Process, a unique concept ensuring simple ordering modal­ities for the customer, a high level of flexibility in making changes up to six days before the start of assembly, precise deadlines maintained in all cases, short delivery periods and much shorter flow times at the Plant. In this case the process is determined not by the vehicle as such planned by BMW in a general production cycle, but rather by the car the customer himself wishes to have and specifies precisely in his order.

Instead of a rigid, pre-determined sequence of production from the Body­shop via the Paintshop to Assembly, the ready-painted body is treated like a component supplied from outside, being kept on hold in buffer areas and delivered to the assembly line just-in-sequence. The customer’s order is therefore only allocated specifically to a certain body upon the beginning of assembly.