BMW Plant | Technology
BMW Production

Paint Shop.

Our State of the Art Paint Facility.

In 1998, over R250 million was invested in a new modern paint facility in Plant Rosslyn. In 2001 a further R300 million was approved for the construction of a new preparation plant which introduced the world's first ever state-of-the-art Vario-Shuttle technology. This has resulted in a Paint Shop that has exceeded all international standards, expectations and ranks amongst the most contemporary of its kind not only in the Southern Hemisphere but also in the globe.

Advanced Paint Technology
Paint technology is essential in creating the optimum visual impression. Applying the paint properly is acknowledged as one of the most difficult processes in modern car production. BMW is committed to using environmentally friendly and technologically advanced processes to enhance the quality of paintwork, both aesthetically and in terms of functionality.

The Paint Shop provides BMW with the flexibility to manufacture cars that are aligned with our customers' specific requests. Apart from the appearance however, a vehicle's paintwork has other just as important functions to fulfil, such as the sealing off of the inside of the car from external noise.

The Process
The Paint Shop consists of two major process areas: preparation and application with a third stage at Final Acceptance. Prior to paint completion, the body shell must go through approximately 20 processes before the final coat is applied.

Preparation
The process starts with the handover from Body-in-White to the Pre-Treatment facility. The main objective of the Pre-Treatment facility is to remove all residues, phosphate and E-coating of the body that could have been acquired in transit. The body is then analysed to ensure that all parts are fully automated and functional. A fully automated Jig checking control station is then installed. This is essential, as the body will be turned upside down throughout the process. The handover station to the Vario-Shuttle is again fully automated where the fixing of the bodies is crucial for the dip curves through the tanks.

The next step of the process is the "Body Wash Station", where 80% of all oily and dirt residues, which are carried over from the Body-in-White, are removed. To achieve this effectively, a spraying system similar to a tropical rain is utilised. The system is filtered with highly effective band filters and all oily substances are separated by centrifuges. This method of cleaning has minimised the amount of water wasted, especially compared to the much shorter bath exchange cycle used in previous systems.

The second cleaning station is a brush washing machine which covers the entire body. The third and fourth cleaning tanks include a full dipping degreasing process coined as the "dolphin jump" movement which ensures that the sections are thoroughly cleaned. The body then goes through two rinsing tanks after which it enters into the phosphate process. The phosphate process makes the first layer of paint more adhesive by growing crystals which create a rough surface that acts as a magnet to attract the E-Coat and also protects the car against rust, this happens in tank seven. Lastly the body shell is dipped in the eighth tank where a process called 'passivation' which prevents the crystals from growing any further.

Thereafter it moves on through an acid zinc phosphate solution (2mμ) crystal structure, which is the basic adhesion primer to make sure that the E-Coat (20mμ) can stick to the substrate inside and outside the body.

This solution reacts with the zinc body surface, forming a dense zinc-iron phosphate layer. The flow of current between the body and the electrodes at the edge of the bath cause the primer paint settle on the rest on the body of the vehicle. Extensive care is taken in ensuring that primer fills each portion and hollow on the car, before the excess paint is rinsed off.

Vario-Shuttle
The most impressive utility in the preparation plant is the Vario-Shuttle. One of the biggest benefits to the previously used chain conveyor systems is that the process time in the chemical bath and the transfer time to the next bath are separated and variable (various dipping curves are programmable). This gives ultimate flexibility to optimise the process for future models with different dimensions. The cleanliness of the E-Coat has improved considerably reducing the re-work (sanding before primer).

The next step is the seam sealer and UBS station. Due to the importance of ensuring consistent applications, the new robotic application is threefold. It provides protection against stone chips, it is a waterproofing layer, and it has sound deadening properties.

In order to reach the required quality levels it imperative for skilled associates to perform in an environment that best promotes efficiency while keeping quality as the main focus. Executive work decks and booths have therefore been installed for a pleasant, improved working environment and excellent lighting and wooden flooring that aim to improve productivity.

Application
The next step is to make sure that all openings on the body are sealed before a primer, which matches the ultimate colour of the car, is applied. The vehicle then passes through a furnace where the primer dries on to the frame and the car then moves to a storage area.

Finally, the top coat, which gives the vehicle its actual colour, is applied. Application of the top coat also involves a number of processes and several layers of paint. The automation of these processes results in extremely smooth, high quality paint work. Prior to the application of the clear coat, the vehicle enters the infrared flash-off zone where the water in the paint evaporates. The vehicle is then polished and waxed using 42 computerised nozzles. This ensures that the wax reaches all parts of the vehicle and as well as prevent rust.

When necessary, electrostatically supported paint application systems are used. This means that the paint is electrostatically charged and the individual paint particles are pulled onto the car like a magnet pull. This procedure guarantees the optimum use of materials, making it possible to reduce overspray by 30%. Plant Rosslyn uses water-based paint which contains 80 percent less solvents than found in conventional paint recipes.

Final Acceptance
The Paint Shop's Final Acceptance area consists of two operations: Finishing and Paint Repair. The Finishing area is responsible for the final finishing on the outer surface, a process that includes the normal flatting, touching-up and polishing that takes place just before the vehicle exits the plant. Contrasting, Paint Repair is an off-line area used in the event of actual paint defects which cannot be attended to on-line.

Protecting the Environment
The Paint Shop Preparation and Application Plant have been carefully structured and designed to take all environmentally aspects into account. The Preparation plant makes use of considerably less water, eliminated chrome 6, as well as lead pollution. Air pollution in this plant is virtually nonexistent, as all exhaust gases are incinerated. About 30% Aluminium can be treated in the process in substrate mix due to the automated membrane filter press which reduces the amount of phosphate and aluminium sludge.

While traditionally environmentally unfriendly organic solvents have been the number one ingredient in conventional paint recipes, the paint and cavity wax used at Plant Rosslyn's Paint Shop are water-based which means that four-fifths of the solvent is replaced by water. This means that when the bodies dry out, the water that goes back into the atmosphere contains a minimum amount of solvent emissions. Using the water-based paint provides just the right conditions for applying the two-component clear paint just before the car is polished. The clear paint not only results in better gloss and brilliance, but because it causes greater surface hardness, it also enhances the vehicle's resistance to environmental factors such as acid rain or bird droppings.

However, it does increase the risk of corrosion on the equipment used in the process because the paint is water-based. Consequently, the materials and machinery used in the Paint Shop have been carefully selected, with most parts made of plastic or stainless steel, in order to avoid this risk. Climate control is also very important when using this type of paint and care must be taken in ensuring that the air fed into the paint booths, as well as the temperature of the paint and body, are kept within the correct specifications.

Aside from water-based paint, a range of other technically advanced features have been introduced to enhance both environmental compatibility and quality: The "clean room", this area includes the primer, top coat and clear coat application areas, as well as the paint mix area. The "clean room" concept serves to eliminate the most common deficiency in any Paint Shop: dust particles falling on and sticking to wet paint. Ultra-fine filters in the air-feed systems over-pressure in the paint application booths, air showers at all entrances, and fluff-free paint suits are all features of an efficient "clean room", and prevent the intrusion of dust particles into this sensitive area.

Sludge Treatment System
The total volume of water in the application plant is 400 cubic meters and this water is only replaced twice a year. Floor water is also recycled: sludge is separated from the water on the floor and the water is then pumped back on to the floor. The water in the spray booths collects the paint overspray, and this water is collected in the skimmer sump. Chemicals are added to coagulate the paint. The denatured sludge then floats to compliment the sludge removal facility. This skimmer water is also treated to insure that the paint does not stick or settle out in the pumps, pipes of flumes of the spray booths and in any of the plant equipment.

Air Filtration
A massive air rectification plant, situated on top of the 16 meter high building, supplies 520 000 cubic meters of air per hour. This air is filtered through five filtering stages and supplied at a temperature of between 24 and 27 Celsius, with the humidity controlled at between 60 and 65%.

Fact Sheet
The total conveyor length inside the Paint Shop is 3 273m.
The Paint Shop is 16 meters high and covers an area of 54 282 m2
Paint shop staff work on two eight-hour shifts, providing 16 hours of operational time.
The Paint Shop can accommodate 210 units per day, and during a 16-hour shift the shop can paint 13 units per hour.
There are 14 Vario Shuttles, each having a maximum carrying capacity of 1 ton, and each weighing 3800 kg.
The maximum speed of the line is 60 meters per minute.

 

 

 

 

Technology
Quality