Planning for the new bodyshop and cathodic dip priming installation was based on achieving a daily capacity of up to eleven vehicles with two shifts per day. At the Hoşdere plant, the full assembly process is completed to the very highest quality standards in record time, whether urban buses, rural-service buses or luxury touring coaches, thanks in part to advanced production methods such as sequenced final assembly and preassembly areas organised based on kaizen principles. These methods help to ensure industrially efficient organisation of the highly-skilled bus and coach production teams. The faster and higher-quality bus and coach production at the Hoşdere plant is also down to the ergonomically designed workstations based on the latest research findings, the introduction of team-based work, an on-going programme of advanced staff training and the implementation of quality gates at the end of each stage of production to ensure consistently high quality standards.

In addition, the Hoşdere plant is a prime example of an ecologically aware production facility in terms of the range of technologies and systems employed as well as the implemented environmental safety measures. By way of example, the waste water from the phosphating plant and cathodic dip priming installation is treated and purified in a separate sewage plant before being fed back into the production cycle, with Western European standards being adhered to at all times.

Body panels are prefabricated on CNC stamping and laser machines at the Davutpaşa plant before being delivered to the bus and coach bodyshop in Hoşdere. In the new bodyshop here, the parts required for constructing the vehicle skeleton are sourced directly from the integrated pipe/tube store. To start with, the pipes and tubes pass through the phosphating plant before being assembled to make the individual vehicle segments at a series of production stations. The individual sections of the vehicle skeleton are subsequently welded together to produce the finished vehicle skeleton at a bodyshell welding station called the „dome“ before being fitted with the necessary panelling. After leaving the bodyshop, the fully clad skeleton is forwarded directly to the cathodic dip priming installation where it immersed completely in the cathodic dip priming bath. After the primer has been applied, the base coat and top coat are added in three separate paint booths.

In the next stage of the production process, the painted vehicle body is forwarded to the final assembly area. In the final assembly hall, the bodyshells are equipped with the suspension system, axles and engine as well as electrical and electronic components. This is also the point at which the interior equipment and appointments are installed. The bus and coach seats are sourced from the in-house seat production facility which is also located in Hoşdere. The buses and coaches are then checked thoroughly to ensure that all of the equipment (engine, electrics etc.) functions correctly and meets the required quality standards. Subsequently the exterior design is customised in the finishing area of the assembly hall. All that then remains is for the vehicle to be put through its paces on the demanding in-house test track. Here the new buses and coaches have to contend with simulated wet-weather conditions as well as negotiate the torture track and other similar stations. Only once a vehicle has successfully passed through all of the quality gates with flying colours can it be handed over to the customer in the delivery hall at the nearby central sales and distribution point.

New structures for optimising production quality

The production structures and processes in the new bodyshop and final assembly area were defined in full accordance with kaizen principles: from the very beginning, production at the Hoşdere plant, like production at all DaimlerChrysler Buses and Coaches plants in Europe, has been based on standardised processes, component pre-assembly near the installation station concerned, assembly-line production, immediate forwarding of all produced parts to the next assembly station once work is complete (one-piece flow) and just-in-time (JiT) buffers near the assembly line.

The new bus and coach bodyshop in Hoşdere

The new bodyshop in Hoşdere now houses pipe/tube parts production for all bus models produced by Mercedes-Benz Türk A.Ş. and the phosphating plant, as well as a frame, flap and seat frame production area, not to mention the bodyshell production line with the „dome“ welding shop, including facilities for all urban bus, rural-service bus and touring coach chassis components. Every sequence in the body-shop is strictly geared towards optimising the overall production process and avoiding unproductive transport or time, all of which has enabled the plant to slash the time it takes to produce each bus or touring coach. Furthermore, in order to ensure highly flexible production processes, new jig and fixture concepts were devised to enable large jigs and fixtures to be manufactured and assembled on site.

To optimise the flow of material at the Hoşdere plant, the JiT buffers have been in-tegrated into the individual production halls. Inside the bodyshop, the individual parts required to pre-assemble the modules are now delivered directly to the relevant assembly line just in time or in kanban container quantities. There are „production islands“ for pre-assembling the individual parts and assemblies right next to the relevant assembly lines. Each individual production station runs on an 80 minute cycle.

This approach has enabled the company to achieve its planned targets with respect to quality (by minimising welding warpage and straightening work), ergonomic design and costs. And the bodyshop can build any Mercedes Benz bus or coach variant it desires (regardless of length, height etc.).

New: phosphating plant and cathodic dip priming installation

In order to ensure optimal corrosion protection for the buses and coaches produced, the Hoşdere plant has introduced the same phosphating and cathodic dip priming methods as those that are already successfully employed at the Mannheim bus and coach plant. The cathodic dip priming installation in Hoşdere – the newest of its kind in Europe and also the first ever to be used for bus and coach production in Turkey – is a sophisticated system incorporating pre-treatment booths for degreasing and phosphating, a cathodic dip priming tank, a rinsing basin, a spray rinsing booth, a manual rinsing booth and a dryer. Measuring 16.5 metres in length, the cathodic dip priming tank is six metres deep and holds 400 m³. Entire vehicle bodies measuring up to 15 metres in length can be immersed in the tank.

All buses and coaches produced at the Hoşdere plant undergo cathodic dip priming as standard. To date the new cathodic dip priming installation has already been used to give around 1,250 bus and coach bodies a flawless corrosion-protection coating. Around two thirds of the new cathodic dip priming installation’s capacity is utilised for entire bus bodies whilst the other third is set aside for luggage compartment flaps and other attachments. These parts are then coated in the powder-coating facility, another new addition to the Hoşdere plant. All of the square tubes and the panels made from steel, as well as the aluminium panels and sections, are coated in the new dip phosphating plant.

New final assembly methods

By implementing efficient production processes and quality controls, the company has been able to further improve its quality standards and adherence to delivery dates. All of the assembly and finishing sequences are based on streamlined, transparent and quality-oriented production processes. Major new developments here include cyclic logistics processes based on the „pull principle“. Logistics experts have succeeded in substantially shortening supply routes, reducing processing times and minimising throughput times by integrating the pre-assembly stations near the installation points, transferring certain assembly tasks from the assembly line to the pre-assembly stations and implementing a raft of additional measures.

Employee encouragement and quality gates after each production stage

The primary aim of the measures implemented to further improve product quality is to eliminate errors in each stage of production, assembly, initial operation and finishing. More than ever before, employees are encouraged to obtain qualifications and identify with the products. The members of the assembly teams organise their work tasks themselves and also receive on-going training. Offices for the foremen, planners and work progress controllers are located right next to the assembly line, meaning that any questions or problems can be resolved more or less on the spot to save time. The introduction of quality gates at the end of each individual production station, coupled with a transparent controlling system, improves the flow of information within and between the individual assembly teams. Defects are detected at an early stage and can be eliminated at source without interrupting the on-going production process. This system has enabled the Hoşdere plant to become a true „learning factory“. And its success is clear to see, since the error rate is falling fast.