RASTATT, Germany - After more than three months of building practice A-class models, the Daimler-Benz plant here is ready for the real thing.
On 9 February, Rastatt will receive production quantities of the vital electronic stability program that makes the A-class stable in the lane-changing moose avoidance test.
At first, ESP supplies from Bosch will be insufficient to allow Rastatt to achieve its full capacity. However, Daimler-Benz will be able to build cars for public sale. The first deliveries to customers are expected mid- to late February.
It will take most of the year to catch up with orders that have piled up since the car was introduced late last summer. More than 100,000 orders have already been received, said Ursula Schnabl, Daimler-Benz spokeswoman at Rastatt.
During 1998 output is expected to be 150,000 cars. But in a full year, Rastatt can build more than 200,000.
When the moose test problem revealed itself on 23 October, ramp-up of the A-class was in full swing. Production had reached about 300 cars a day. And, apart from a long New Year break, it never stopped. Production was, however, reduced to 150-200 cars a day. Employees' basic hours were not cut, though the company did not take the pre-arranged option of weekend and night shifts.
As availability of the ESP control unit increases, production will rise and more shifts will be worked. By June or July, the Rastatt plant should reach full production, operating a total of 91 hours a week. It does not operate on Sundays or public holidays.
'Morale was, of course, hit when the moose test failure occurred,' said Schnabl. 'It was not pleasant to find journalists waiting at the factory gate at the end of every shift asking workers if they'd been paid recently. However, the employees were fully behind the A-class. Most had been given the opportunity to drive the car and they had been impressed by it. They really had confidence in it.'
The production facility has had to undergo only a few changes as a result of the modifications, said Thomas Will, logistics engineer.
'The ESP had, in any case, been planned as an option due for introduction later in the year. We just had to speed up its integration into the vehicle,' he said.
An additional robotic cell had to be introduced to weld on a new support that was required for an ESP sensor, and operators had to be trained to mount the sensors and the additional wiring involved.
Rastatt keeps manufacturing costs to a minimum by emphasizing a lean production organization. Many features are new to Mercedes production.
A first for the Daimler-Benz group is the supplier park on the Rastatt site.
Seven suppliers are located there, and three others rent space within the body shop, which is the former assembly shop of the E-class.
'By building up the physical volume of parts such as seats on the site, we can reduce transport costs,' said Will. 'We have reduced the volume of transport required by 60 percent and the distance traveled by 6.1 million km per year. The number of deliveries to the suppliers on the site is only 40 per day whereas otherwise 110 would have been needed.'
Companies at the supplier park have contracts for the life of the A-class, which is likely to be about six years.
'The site is big enough to take another model,' said Schnabl. 'We are hopeful it will happen though no decision has yet been made. Both Daimler-Benz's other facilities in Bremen and Sindelfingen make more than one model.'
All 175 A-class suppliers are single-source suppliers, which is a strategy spreading through the Daimler-Benz group. The higher volumes involved bring cost benefits.
The supplier park concept is already spreading to other plants. According to Will, Sindelfingen started a similar initiative last year, though the park there has to be outside the site because of lack of space.
At Rastatt, the supplier park is linked to the A-class assembly hall by an 80-meter-long tunnel. Automatic transfer systems move parts in sequence directly from the suppliers' production lines to the place on the assembly line where they are to be mounted on the vehicle.
The A-class production sequencing system is also a pilot for Daimler. It aims to freeze customer orders 10 days before a vehicle is built. Knowing what customers have chosen, the suppliers and sub-suppliers can plan their own manufacturing activity. It gives them the best chance of achieving lean production.
'We are trying to eliminate the wasteful stocking of parts both in our production facility as well as at our suppliers' plants,' said Will.
From start to finish, A-class production takes about two days. Each car is made to a customer order. Once the order backlog has been cleared, European customers should be able to receive their car just three weeks after ordering.
The new sequencing system is a dramatic change for Daimler-Benz.
'Mercedes customers expect their cars to be built exactly to their wishes, and they are used to being able to change their mind up until the last minute,' said Schnabl.
At the Bremen and Sindelfingen plants, where the same sequencing strategy is to be adopted, production personnel will also have to adjust their patterns of thinking. 'They are used to working with the output date for a particular customer's order,' said Will. 'Now they will have to work the other way round.'
The A-class has been cleverly designed for production.
Only four different bodies are currently made. They are symmetrical, so they can be used for either left-and right-hand drive versions, said Schnabl. The variations concern openings in the roof for a sunroof and a mobile phone antenna.
A fifth design exists, but is currently not produced.
'It was developed for the US market,' said Schnabl, 'but Mercedes dealerships there say the A-class is a car for crowded road conditions and not suitable to North America.'
Automated body shop
Most of the large stampings are delivered to the A-class body shop by rail from Daimler-Benz factories in Bremen and Sindelfingen.
The body shop is almost 100 percent automated, said Olaf Dunkler, manager of strategic projects. About 320 robots assemble the 290 panels required for one body using 3,700 spot welds. Robots perform both handling and welding tasks where possible, he adds.
Kuka supplied all the robots. Comau, the equipment subsidiary of Fiat, did much of the systems engineering.
Laser sensing is used for the precision mounting of cars on bodies. Sensors located around the door opening tell the robot where to mount the door hinge with a precision of 0.3mm, which eliminates manual adjustment later. 'Without the sensing system, we could not be sure of the precision achieved,' he said.
By using glue as well as welding, the passenger compartment is strengthened without added weight, said Dunkler. Kuka robots perform the gluing, while Renault Automation supplied the fully engineered cells.
Because subsequent welding operations destroy the sealing properties of the glue, sealant is applied when bodies pass through the paint shop.
New paint technology, developed jointly by Daimler-Benz, BASF and Duerr, has been employed for the first time on a large scale. The companies claim it reduces paint consumption by 20 percent and almost eliminates the need for solvents.
Whereas five coats are generally required, the A-class uses only four coatings. They are formulated to give the same resistance to UV light and to corrosion as the normal five.
The first coat, the primer, contains a secret ingredient which enables the paint to work without using lead. The base and top coats consist of water-based paint, which is sprayed on electrostatically.
The final clear coat, which is also sprayed on, is composed of a powder slurry which does not contain the solvents usually required by the widely used, more conventional two-component paints.
This is totally new painting technology. Other Daimler-Benz plants are waiting to evaluate Rastatt's experience. BASF and Duerr will not sell the technology outside Daimler-Benz for two years.
Interior painting and sealing tasks are carried out by robot before the bodies leave the paint shop.
The A-class is available in 10 colors. To minimize changeover time and paint waste, the optimized sequence through the paint shop allows for a minimum batch size of five and a maximum of 20.
Before and after painting, bodies pass through a fully automated buffer store with space for about 400 bodies. If problems have occurred in the body or paint shops, the original sequence can still be adhered to in the assembly shop.
'Realistically, we expect cars coming out of the body shop to adhere to the original sequence with an accuracy of 98 percent. Those from the paint shop will have an 85 percent accuracy,' says Dunkler.
Processes used in the assembly shop are mostly conventional. The level of automation is just 10 percent. 'We automate up to a certain point and then let the operator take over. A person has better sensitivity about how screws really fit than a robot,' says Dunkler.
Robots are used for mounting weather strips around door openings, which is one of the newest robotic applications to be developed by car manufacturers. They are also used for traditional tasks such as mounting seats, putting in windows, batteries, roof linings and sunroofs. The tailgate, which is supplied as a complete ready-painted module by Peguform, is also mounted on the body by robot.
A separate assembly loop adjacent to the main line is for the chassis. Daimler-Benz factories supply most of the chassis components. Once completed, the chassis and body are brought together and automatically assembled.
At each end of the assembly shop is a covered area where trucks drive in to deliver components. They are directed to the northern or southern receiving area depending on where their load is needed in the assembly process.
By volume, 70 percent of components are delivered in sequence and just-in-time. More than half come from the supplier park.
Later this year, a supplier monitoring system is to be introduced, said Dunkler.
'We'll start grading suppliers and develop a Top 10 list,' he said. 'Where there are problems we'll work together to find a solution.'
A continuous improvement program is also under development. The factory is organized into teams, with each shop floor manager supervising 12 operators.
'We plan to set up multidisciplinary teams on the shop floor and to give them time to discuss continuous improvement ideas,' said Dunkler. 'They'll be given efficiency goals to achieve.'