Four-cylinder diesel engine (OM 651), Part 2

Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engineMercedes-Benz OM 651, new generation of four-cylinder diesel engines

Stuttgart, October 13, 2008 – When it comes to the production of the new four-cylinder diesel engine generation, Mercedes-Benz has taken significant steps to extend its own production facilities and installed state-of-the-art production processes. The close relationship with development and intensive cooperation have enabled the set-up of the plant and production processes to be optimised significantly. Mercedes-Benz is expected to produce more than half a million engines per year featuring the best power output, consumption and emissions values among the diesel engines of their class. The four-cylinder engines will be produced entirely in Germany in the Mercedes-Benz Powertrain co-ordinated production system – the basic engine originates in Untertürkheim, while final assembly takes place in Kölleda/Thuringia. Components are supplied from additional Powertrain sites in Germany. Mercedes-Benz has invested a total of around half a billion euros in new plant and technology for the production of the new diesel generation.

Crankcases and cylinder heads are machined in a new, approx. 17,000 square metre building

Crankcases and cylinder heads are machined in a new, approx. 17,000 square metre building

To achieve the best possible efficiency using state-of-the-art technology – this is the ambitious aim which both engine developers and production experts have set themselves for the new generation of four-cylinder diesel engines. Producing 150 kW / 204 hp and 500 Nm (368 lb-ft) of torque, the 2.2 litre engine occupies the number one position in its segment. The C 250 CDI BlueEFFICIENCY Prime Edition premiere model can accelerate from a standstill to 100 km/h (62 mph) in just 7.0 seconds, on the way to its top speed of 250 km/h (155 mph), and consumes 5.2 l/100 km (45.23 mpg/US, 19.23 km/l), with CO2 emissions of 138 g/km. For production of the new generation of engines, Mercedes-Benz has developed new production technologies combining a high degree of flexibility with precision and quality at the highest level. 

Production-compatible engine-design from the outsetMercedes-Benz Powertrain co-ordinated production system

An optimum production strategy can only be achieved through intensive cooperation between development, the production divisions and parts suppliers. No fewer than 1,000 processes were jointly developed in the workshops and implemented together with colleagues from development. These included, among other things, materials processing in an optimally structured process and improvement of ergonomics at the workstations. One of the results of this intensive cooperation is the elimination of blind and overhead work during engine assembly. Another example: the engine has timing windows and brackets which allow checks to be made at a glance as to whether the gaskets have been correctly installed. Moreover, all of the assembly steps were put through their paces in advance in a so-called prototype plant.

Significant site investment for engine production

The engine is produced exclusively in the Mercedes-Benz Powertrain co-ordinated production system in Germany. The crankcase, crankshaft, cylinder head, connecting rods and fuel components are manufactured in Untertürkheim, where the basic engine is also assembled. The oil pump and camshafts are produced in Berlin. Final assembly, testing and shipment of the engines to the vehicle plants take place at MDC Power GmbH, a wholly-owned subsidiary of Daimler AG in Kölleda, Thuringia.

Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engine

Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engine

For production of the powerful yet economical CDI engines, Mercedes-Benz has set up its own special production facilities in Untertürkheim. A new two-storey extension building has been added to the existing production buildings specifically for this purpose. The newly constructed building stands on huge reinforced concrete pillars and beams weighing up to 120 tonnes. Investment in this building alone amounted to more 20 million euros.Mercedes-Benz Powertrain co-ordinated production system

With an area of around 17,000 square metres, the new building is where the crankcases and cylinder heads are machined, and the cylinder heads also assembled. For logistical reasons, the building complex is ideally placed for the basic assembly of the engine, which takes place in an available area located in the opposite building.

MDC Power GmbH, engine plant in Kölleda

MDC Power GmbH, engine plant in Kölleda

In addition to Untertürkheim, Mercedes-Benz has also invested in MDC Power GmbH in Kölleda for production of the new engine generation. A new assembly shop has been set up there for final assembly. From the autumn of 2008, more than half a million units of the new high-tech engine are expected to roll off the production line of the Powertrain co-ordinated production system.

Modular production plants for increased flexibility

The aim during production is comprehensive quality assurance

The aim during production is comprehensive quality assurance

The production plants for the new four-cylinder diesel engine have been set up primarily as modular units within the individual installations, which makes for flexible levels of configuration. For example, initially a production line with a capacity of 250,000 units per year (expandable to higher units) was installed for crankcase production. Six months later, this was followed by a second identical production line, set up in parallel – the time difference enabled the experience gained from setting up the first production line to be put to good use. The benefits of the lessons learned include a high degree of flexibility in terms of unit quantities and also demand-led use.

New production technologies developed in-house

With its innovative machine systems for production of the new four-cylinder diesel engine generation, Mercedes-Benz is pioneering new production technologies. When machining the connecting rods for example, the tools no longer go to the workpiece, but rather a workpiece pallet brings four connecting rods per work cycle to the tool, which is installed in a fixed location.

The cylinder heads are assembled and passed on by robots using a "pick and place" approach

The cylinder heads are assembled and passed on by robots using a “pick and place” approach

New ideas were also brought to the table when it came to transferring the workpieces. The production specialists at Mercedes-Benz developed a new work principle in which robots assemble the cylinder heads with simple and robust grippers using a “pick and place” approach – they retrieve their workpiece and then, after assembly, pass it on to the next step for further processing. In this way, individual stations no longer need to be linked to each other in terms of logistics, since the robots also handle the transport of the parts, all of which makes it possible to design a very compact assembly line. As such, it has been possible to save on a large amount of space which would otherwise have been taken up by a conventional daisy-chained system. 

Polished production logistics

MDC Power GmbH, engine plant in Kölleda

MDC Power GmbH, engine plant in Kölleda

Trouble-free assembly is taken care of thanks to a polished logistics system. Crankcases and cylinder heads are always available at precisely the required time for assembly (just in time); similarly, large-volume parts are fed through sequentially. Smaller components are provided in set boxes, appropriately placed directly on pallets so that they can be picked up. After assembly of the basic engine in the Untertürkheim plant, the unit is transported to Kölleda for final assembly and dispatch to the vehicle plants. Here, an 18,000 square metre assembly shop and a 16,000 square metre supplier logistics centre have sprung up just within the last six months.

Modern testing technology for quality at the highest level

Production is geared towards fulfilling the aim of maintaining quality at the highest level. To achieve this, the production specialists use the very latest methods for comprehensive quality assurance. This includes highly sensitive camera stations, for example, located downstream of the many work processes. Even if an employee should suffer a momentary lapse in concentration, the cameras automatically check whether all of the assembly steps have been carried out precisely as required and if necessary sound an alarm so that the issue can be immediately rectified.

The production specialists examine the components in detail

The production specialists examine the components in detail

The results of work carried out by automatic stations are also meticulously tested and all data relating to the assembly processes are normally retained for several decades in a product life cycle file (PLA).

The cylinder heads are assembled and passed on by robots using a "pick and place" approach

The cylinder heads are assembled and passed on by robots using a “pick and place” approach

The individual test procedures comprise, among other things:

  • Piston cooling unit test: cameras monitor the geometric contour of the oil injection nozzles in order to guarantee optimum cooling of the pistons. 
  • Monitoring of the torques and tightening angles of bolt connections when assembling the pistons and cylinder head using electronic wrenches. 
  • Oil and water jackets are checked for seal-tightness after assembly of the basic engine using compressed air. 
  • Cold test: Mechanics, oil pressure, air flow and leakage integrity of the entire engine are checked in a cold test at the end of the assembly line using the very latest technology. Each engine is subjected to this test before it can be released for dispatch. 
  • Acoustic test: The acoustic test measures the engine’s structure-borne noise using a laser vibrometer. 

Mercedes-Benz Powertrain coordinated production system, OM 651When it comes to quality tests, the specialists are not satisfied just with spot tests, but rather each individual engine must pass all tests. This helps to ensure that each unit meets the high quality standards. Thanks to these innovative production methods, the new generation of four-cylinder diesel engines is not only leading the way in terms of power output, consumption and emissions, but is also exemplary in the areas of production and quality. 

Integrated environmental protection

Since 2005, the Untertürkheim plant has also made extensive use of the award-winning principle of dry machining. Using micro-lubrication, the smallest quantities of lubricant are mixed with cold air and used instead of the usual cooling lubricants. The technology was developed in a cross-departmental process in Untertürkheim with the support of external specialists from universities and suppliers. After pilot tests carried out back in 1997, the project team implemented the process for the production of wheel carriers in 2001. Gradually it was possible to introduce the process into other production areas, almost completely replacing the role of cooling lubricant.

Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engine

Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engine

Previously the machining of complex components such as crankshafts or cylinder heads called for enormous quantities of cooling lubricant, which is produced from crude oil and has requires energy and cost-intensive recycling. Thanks to this new process, however, it has been possible to reduce the quantity of lubricant significantly. The quantity used in dry machining is a fraction of the amount of lubricant which would otherwise be needed. This saves valuable resources and also contributes to improving work safety. Another advantage is that dry machining does not need anywhere near as space in terms of production area, since costly recycling and colling equipment are no longer necessary.

Engine production: Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engine.

Engine production: Efficient and environmentally-acceptable production methods for the new four-cylinder diesel engine.

The process represents a significant contribution to the progress being made in the area of environmental protection and sustainability, and as such in 2005 it received the “Environmental Leadership Award.” This award is presented annually by the United Nations Environmental Programme (UNEP) and Daimler AG.

See also the new generation OM 654 diesel engine here.

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