BMW Werk München (Munich Plant) is the company’s main factory, with 10,000 workers producing ca. 800 3er Series autos and 1,200 engines each day.  The plant is located in the middle of Munich, adjacent to BMW’s Vierzylinder corporate headquarters building and the BMW Welt delivery and experience center.  Each car is built to customer specifications and, given the multitude of options, colors, and engines available, the Munich factory typically builds only two of the very same car each year.

My 335d’s production started on 2 December with a coil of steel that was unraveled

Press Shop

and cut into plates that were then pressed into the right shape.  The Press Shop handles 600 metric tons of steel plates each and every day and the steel is specifically selected for individual parts in order to meet BMW’s high standards.

Depending on the part, four to six production steps are required.

The parts formed for the 335d were then assembled in the Body Shop starting on 8 December until the car body was completed later that day.

The Mobi-Cell with handling and welding robots.

Large panels simultaneously converge into a central spot for spot and laser welding as well as other joining techniques such as gluing. Robots seem to magically  create the chassis by turning and rotating different parts.  The robots in the Mobi-Cell perform spot welding with exacting precision.

The remarkable “Mobi Cell” Body Shell Concept is a BMW manufacturing innovation.  Mobi Cell stands for “Mobile Standard Fertigungszelle” (mobile standard production booth). It makes it possible it to shift production stations within the body shop  quickly and economically. The individual station can be combined with and connected to larger and more complex manufacturing stations, thereby  improving the factory’s flexibility and ability to cope with changes in demand.

Paint Shop.

The next step in production is the Paint Shop. The 335d’s chassis was cleaned, dipped into a phosphate solution that serves as a foundation for additional layers of paint, and then four layers of color were applied in separate passes. First the primer was applied in the cathodic rotation dip, then filler, base, and clear coat were applied by robots and painting machines.

The cleaning stage was very thorough, using a blow cleaner with high speed airflow and rotating ostrich feathers. The 335d’s  finish could easily have been ruined by the tiniest piece of dust so BMW uses ostrich feathers, which are very efficient at gathering dust, before sending the car to the primer booth.

Robots began the priming process by spraying the body’s interior.  Then the car moved to another paint booth where mists of electrostatically charged primer were attracted to the body’s surface.

Afterwards, the car was transferred to an oven. This was followed by another dusting with ostrich feathers and finally the car received its base coat of color, Montegoblau metallic (Montego Blue metallic). After another trip to the oven, the 335d received its clear coat, which gives the car its sheen.

Tilt conveyor

As the 335d entered the assembly process, it received its Vehicle Identification Number (VIN) and several thousand parts, based on what we ordered, were fitted to form a complete vehicle.  In this case, options included leather seats, BMW Assist, Navigation, iPod integration, Style 195 wheels with performance tires, oyster leather sports seats, light burl walnut trim, sports suspension, Comfort Access keyless entry, rear and side shades, heated front seats and steering wheel, park distance control, High Beam Assist, and BMW ConnectedDrive.

The 335d continued along to the Tilt Conveyor which facilitated access to the underside of the car by tilting it on its side so that fuel and brake lines and gas tanks could be fitted.  Afterwards, the car’s doors were removed and assembled separately.  A sophisticated logistics process ensured that the same exact doors were refitted to the car later in the process.

At the wiring station, wiring harnesses were installed to support the hundreds of electrical connections in the 335d.  Workers then routed wires through the engine compartment, interior, and trunk as neeeded.  One team began to install interior parts including dashboard, seats, and headliner, while another team installed a variety of components including the master cylinder and heating and air conditioning systems.

The windshield was fitted by a robot, one of the few processes at this stage done by a robot, not by humans. First an adhesive is put on the glass. Then the robot installs the windshield with laser precision.

"Wedding"

Final assembly includes installing the six-cylinder diesel engine (built in Austria at BMW Werk Steyr), which was connected to the front suspension and transmission.  The complete powertrain was preassembled on a crossmember.  In what is referred to as the “Marriage” or “Wedding,” the chassis was joined with the power train. On the right side there were 4 robots that bolted the drivetrain to the chassis. It was a marriage ceremony that was completed in seconds.  The wedding was the beginning of the last production stage.  Workers then made all exhaust and under-hood connections.

The 335d’s front end (fenders, headlights, bumper, kidney grills) were fitted, Wheels and tires were mounted and the 335d touched the ground for the very first time.  Just before leaving the assembly line, the car was fueled, brake fluid and coolant were added, and the 335d’s keys were encoded.  Workers tested all electrical components and instrumentation and the fit and finish of the 335d’s hood, doors, and trunk were inspected.

The Roll Booth.

Finally, on 10 December, the assembly process was complete and the long-awaited moment came: the 335d was started for the first time.  There were, however, more tests: at the roll booth, a four-minute test simulated a variety of driving conditions such as stop-and-go traffic, acceleration to 160 km/h, and driving uphill and downhill.

As the 335d exited the roll booth, there were more tests and inspections.  Every BMW has to be visually, technically, and functionally perfect before it will be permitted to leave the plant.  As it was driven to the end of the assembly line, the 335d was checked by numerous workers for possible defects and allowed to continue on its way.  It was ready to be transported to the BMW Welt for delivery on 23 December.