Sustainable operations have high priority at Audi. That’s why we are continually further developing our production technologies. This is the only way for us to live up to our high demands in terms of quality, environmental compatibility and energy efficiency. With the construction of the new paint shop, we placed great importance on high standards of resource efficiency and ecology.

—Prof. Dr. Hubert Waltl, Member of the Board of Management of AUDI AG for Production and Logistics

With the bell‑bell method, paint is applied only electrostatically, thus achieving higher efficiency. In combination with dry separation, this also benefits the environment. Five‑percent less waste (paint sludge) is created for each car that is painted.

“Bells”—rotary atomizers—have a significantly higher transfer efficiency rate than conventional spray guns (non-electrostatic and electrostatic). Until recently, a standard process was to use a bell-gun approach, with the rotary atomizer applying the first base coat; the spray gun applying the second base coat; and resurfacing with a spray gun.

The bell-bell approach, by contrast, uses the rotary atomizers to apply metallic paints for base coating AND resurfacing. This process matches the colorimetry of applied colors with far greater deposition efficiency than spray guns (transfer efficiency of approximately 65%, as opposed to 30% with a spray gun), according to SAMES, a provider of spraying and finishing systems.

In addition to the material cost savings resulting from a bell-bell process, manufacturers will also see savings due to reduced hazardous emissions as well as reduced spray booth cleaning frequency, according to robotic systems provider Fanuc. Dirt related defects can be reduced because higher transfer-efficient bells generate less overspray than spray guns and consequently less paint buildup on equipment.

Quality improvements can also be expected with a bell-bell process, Fanuc said. This is due to the improved ability of a bell to atomize the paint compared to a spray gun. The bell-bell process can improve overall paint film uniformity, especially if robots are used as the automation equipment transporting the bells.

Electrostatic painting of the car body with the bell-bell method. Click to enlarge.

The complete topcoat painting process for an Audi model lasts about three hours. The car bodies pass through three stations for the application of filler, basecoat and clear paint. After each step of the process, the painted car bodies pass through a drier.

Audi places great emphasis on efficiency also with this equipment: The energy required for a constant temperature in the drier cabins is optimally adjusted to the number of car bodies to be dried. Hot air passes through special air vents pointing towards the car bodies.

The new topcoat line is also a further component of the fully connected intelligent factory of the future. For example, a big‑data robot measures the painted automobiles at more than 100 measuring points. Employees use the data on quality collected in this way to compare with existing process data. This comparison helps to prevent possible production flaws in the electronic quality process, with support from an electronic quality inspection.

For this purpose, touchscreen clients are used that work like tablets and provide the employees with the collated data in direct and indirect areas. This means that all of the departments involved in the production process are connected and can work with the latest data.

Audi places great importance on the ergonomic design of workplaces. For example, height‑adjustable platforms in the new paint shop allow an optimal working environment. Handling devices such as lifting aids for the car hood and tailgate assist the employees in the working process. Another new feature is the worker conveyor belt, which carries the employees when they are working directly on the car bodies. Instead of using stationary tool stations, items such as polishing machines and paste are always within reach in the trolley carried next to them.

Up to 900 car bodies a day can be painted on the three floors of the 12,000 square meter building (129,000 sq. ft.). Approximately 200 employees work in the new paint shop in three‑shift operation, supported by 54 painting robots, 36 handling robots and eight cleaning robots.

Start of construction of the new hall, which is 324 meters long, 36 meters wide and 32 meters high (1,063 x 118 x 105 ft.), was in April 2014. Installation of equipment started in March 2015 and the topping‑out ceremony was in July. Series operation began in spring 2016 after a construction period of just two years.

At present, 650 car bodies are painted there each day; the maximum daily capacity of approximately 900 cars per day is to be achieved by the end of the year. The models Audi A4 and A5 are currently painted in the new paint shop, later to be followed by the Audi A3 and Q2.