Mercedes-Benz minibuses, model year 2012
Mar 29, 2012
Top quality as the basis for success: production of Mercedes-Benz minibuses
  • The crucial difference: seamless quality
  • Body-in-white: stripped down to the bare essentials
  • Paintwork: individual colours applied with great care
  • Assembly: custom-made buses on four lines
  • Finishing: meticulous inspection prior to extensive test drive
  • Exhaustive quality control extends beyond delivery; top qualified staff, high standard of training
Four model series, 14 models, 26 variants, market-leading position in Europe, deliveries to 40 countries on four continents – the minibuses from Mercedes-Benz are an ongoing success story. The production output of Mercedes-Benz Minibus GmbH in Dortmund ranges from indivi­dual units to large-scale orders. A recent example is 45 buses for the Eurovision Song Contest which is to take place in Baku/Azerbaijan at the end of May. The success of the Mercedes minibuses is founded on top quality from the plant in Dortmund.
The crucial difference: seamless quality
Fitting out panel vans, modifications to the body-in-white such as the incorporation of large entrances and extended rear ends, add-on equipment produced in-house and even low-frame chassis designed specifically for the spectacular three-axle Sprinter City 77 – production operations in Dortmund match diversity with professionalism.
The professional approach includes close coordination with the development team at Mercedes-Benz Vans in Stuttgart and the van factories in Düsseldorf and Ludwigsfelde. This ongoing collaboration ensures that the specialists at Minibus GmbH are informed of changes in good time. Necessary modifications to bodies and chassis for bus production are coordinated in detail, along with corresponding increases in load capacities.
Extensive tests such as braking trials with laden vehicles at the test site in Papenburg in connection with load uprating projects provide a reliable basis for modification measures. The entire scope of procurement and production operations and the complete order process are carried out in accordance with Mercedes-Benz's stringent guidelines and procedures. Guaranteed seamless quality is one of the special merits of minibuses from Mercedes.
This clearly sets Minibus GmbH apart from other fitting and bodybuilding companies. The resultant quality is keenly appreciated by customers, assuring minibuses from Mercedes-Benz of market-leading status in Europe. This position is to be consolidated by the current expansion of production capacity from 1100 to 1300 minibuses annually.
Body-in-white: stripped down to the bare essentials
The basic vehicles for minibuses arrive by truck from the plants in Düsseldorf (Sprinter panel van) and Ludwigsfelde (chassis). Prior to beginning production operations, they are first of all dismantled: attached parts such as bumpers, radiator grille, headlamps, tail lights, and the Mercedes star are removed along with doors, cab seats, side windows and tanks. On chassis, the focus is on removing rear axles and drive shafts.
All parts are stored on order-picking trolleys on a vehicle-specific basis in the logistics area and subsequently returned to the assembly line as and when they are required. The cockpit remains in the vehicle, but is carefully covered up and reliably protected against damage and soiling.
Going to great lengths for panel vans
Production operations in the area of the body-in-white are carried out on three lines. A typical item of work on the body-in-white when converting panel vans entails producing larger cutouts for doors. To this end, the sheet metal of the side wall is cut out and replaced by a mounting frame made of glass-fibre reinforced plastic. Reinforcements and cutouts for air conditioning systems, roof fans, roof hatches or destination indicators are also produced here, along with lowered wheel arches to provide increased legroom in the passenger compartment.
Another prominent area of work entails rear extensions in glass-fibre reinforced plastic incorporating a tubular frame for reinforce­ment purposes. These extensions are bolted to the rear of the longest panel van variant, after removing the rear wall. These models are additionally provided with enlarged window cutouts towards the rear. The rear extensions take up the Sprinter's exterior stylistic features and are perfectly integrated into the overall design.
Framework-body vehicles: cathodic dip priming stops corrosion
For framework-body vehicles, the entire structure of the bodywork to be attached is prefabricated and supplied ready for assembly. As on the large buses from Mercedes-Benz, cathodic dip priming provides the framework with reliable protection from corrosion. Conversion measures for larger passenger entrances are carried out on the cab in a similar manner to on the panel vans.
A special vehicle is the Sprinter City 77. This three-axle bus accommodating up to 40 passengers is provided with its own low-frame chassis. It is supplied as a complete framework body, including the mounts for the independent wheel suspension on the rear axles.
The next step for framework-body vehicles entails attaching the rear end and roof and fitting the glass fibre-reinforced plastic side panelling. These parts are fitted by means of a bonding process. Cutouts for roof hatches and air conditioning are produced as on panel vans.
Paintwork: individual colours applied with great care
Only the necessary parts are painted – on panel vans with rear extension, for example, only the rear end is painted, rather than the entire body. Parts where the existing body has been modified, such as the passenger entrance, are also painted. Window openings in the body are carefully masked off before painting. Seams and framework are also primed and painted.
The body is then cleaned and degreased before carrying out filling and grinding work. Priming and filling take place after a further cleaning process. Only then is the top coat applied. Metallic paints are additionally clearcoated. The painted body is subsequently polished to a high-sheen finish.
The choice of individual paint finishes is virtually unlimited: over a hundred paint finishes are available from the van factories in Düsseldorf and Ludwigsfelde, enabling Mercedes-Benz to fulfil virtually any colour wish. The same applies to the attached parts, which are painted separately by specialists in a manual process to produce a high-quality finish.
To ensure perfect protection against corrosion, the painted minibuses are subsequently transferred to vacuum chambers. Here cavity sealing takes place, the remaining underbody protection is applied and protected with a wax coat.
Assembly: custom-made buses on four lines
Fitting the interior equipment and appointments in the minibuses is a particularly labour-intensive matter. A staff of around 100 are employed in this area – almost half of the total workforce. Production is carried out on four lines, distinguished according to model series and the scope of work in hand.
Extensive pre-assembly work takes place in the same shop in parallel with the fitting work. Floor coverings are cut to size, windows are provided for the specific vehicles concerned, fittings are prepared for additional bus-specific switches and the vehicle electrical systems are prepared with individual cable harnesses. Ceilings, luggage racks, air conditioning channels and panelling are pre-assembled. Last but not least, modifications are carried out to the drivetrain, doors, grab rails and partitions are prepared and seating is provided. Supply to the relevant points on the assembly line is carried out along short routes with order picking trolleys by means of a transverse delivery setup.
Extensive work breaks down into eight stages
The assembly process for each bus comprises eight stages, each entailing an extensive scope of work. The process is begun by applying the desired decor to the floor and fitting the windows and roof hatches. The electrics are then installed, after which the vehicle proceeds to a high-level station. Chassis-related work under the vehicle is carried out here, such as modifications to the drivetrain, fitting of the retarder along with the rear axle, fuel tank and exhaust. Above all, the components and parts which were initially removed upon delivery of the panel van or chassis are refitted here.
Back on floor level, work continues with the interior panelling, luggage racks and air conditioning channels, convectors, tunnels and the appurtenant drives. In the final two stages the interior fitting work is completed. This most obviously involves the seating, grab rails, partitions and curtains. Fluids are checked and batteries installed.
Finishing: meticulous inspection prior to extensive test drive
The assembly process is followed by finishing touches and final inspection. Markings are applied and if a destination indicator is on board the corresponding programming is carried out.
Each individual bus then undergoes meticulous inspection. This extends from checking that all items of equipment and appoint­ments are complete to verification of the seat spacing for licensing purposes. Staff also check the quality records for all stages of the production process. This does not yet mark the end of the process: every minibus is now sent out on an extensive test drive. This is carried out on public roads and lasts around half an hour. When modifications have been carried out to the roof, a leakage test is also obligatory. Only then is final inspection carried out and the bus finally approved. The new bus is delivered either directly to the customer or to the competent sales office. Depending on the model and scope of equipment and appoint­ments, between ten and 35 days elapse between the start of production and final approval.
Exhaustive quality control extends beyond delivery
Quality is accorded central priority in the production process. Production of the minibuses is subject to the same high quality standards as apply to Mercedes-Benz Vans. As at all plants throughout the group, the GPAS global product audit system provides the basis for quality assessment. Rather than being assessed solely in relation to individual cases, in this process quality is measured precisely by reference to comparable parameters.
All production processes are subject to quality controls. The last check on all manufactured minibuses takes place in the final inspection process. A staff of three is assigned to this work, ensuring quality assurance independent of the production department.
The quality of the minibuses from Dortmund is fully on a par with that of their big brothers bearing the Mercedes star. This is also confirmed by the customers, who are surveyed by an external service provider as to their satisfaction six weeks after delivery. The results of this survey are fed back to Dortmund, where they undergo in-depth evaluation in the fault tracking process.
All quality assessments from the production process, final inspection and subsequent surveys are fed back to the depart­ments concerned. In case of discrepancies, measures to eradicate the problems concerned are undertaken at once. Independently of such problems, awareness and information measures are carried out on the topic of quality, together with corresponding workshops.
Top qualified staff, high standard of training
Apart from the precision production process incorporating in-depth testing and inspection and employing high-quality and tested parts and components, top quality hinges first and foremost on motivated and well trained staff. Qualified specialists are employed throughout the minibus production process.
Against this background, Minibus GmbH is particularly concerned with fostering young blood – trainees account for around ten percent of the workforce. Dortmund offers apprenticeships in five occupations: assembler and bodywork specialist, mechatronic automotive engineer, vehicle painter, warehouse logistics specialist and office administrator.
Completion of the apprenticeship phase does not mark the end of the learning process at Mercedes-Benz, however: at annual performance review meetings, the qualification needs of each employee are determined and a corresponding training plan is drawn up. In this way it is ensured that the knowledge and skills of all members of the workforce are kept up to date.
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