Fine Boring Tools Reduce Processing Costs By Around 40 Percent

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At the Nuremberg (Germany) plant of the commercial vehicle manufacturer MAN Truck & Bus, production of a highly efficient new 3.4 US gallons diesel engine has started. Fine boring tools from Mapal are used for the cylinder heads.

Practically at the same time, MAN has launched two important future projects at its Nuremberg site. Parallel to the start of production of the new diesel engine, a battery series production for the manufacturer's electrically powered vehicles has commenced. At more than 50 assembly stations, up to 50,000 batteries are set to be manufactured annually—with the option to increase this capacity to 100,000 high-voltage batteries by 2030. At over 115 feet in height, the new building is the tallest production facility at the site.

Directly opposite, on an area of 248,000 square feet, is the production of diesel engines. As a process planner, Marco Singer is responsible for the manufacturing of the cylinder heads for the completely newly developed D30 engine. Opposite Hall M17 is the newly established battery production. Marco Singer assesses the transformation to electric drive as follows: "For various applications such as urban traffic, the electric motor is the ideal drive. However, in other areas, diesel will remain for a long time." He cites agriculture, marine, and military use as examples. For the future, a mix of different drive technologies will therefore be necessary.

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One Engine for All Brands

The Traton Group, which includes MAN, Scania, Volkswagen Truck & Bus, and International Motors, relies on a modular system, the Traton Modular System (TMS), whose components are used across brands. True to the motto "You don't have to reinvent the wheel," the group efficiently pools its resources this way. The D30 engine serves as the common engine platform for the entire group. Everything from development to mechanical production, engine assembly, and delivery to the various vehicle manufacturers takes place at MAN in Nuremberg, Germany. Until three years ago, the site also housed its own foundry.

The D30 engine is based on a platform but is produced in six different performance levels ranging from 360 to 560 horsepower. It is the largest standard engine in the portfolio and is intended for use in various vehicles, with the focus being on 44 short tons trucks in the truck sector. The D30 replaces the previous D26 and D15 engine series. The innovative engine achieves a maximum efficiency of 50 percent and consumes five percent less fuel than its predecessors, which equally reduces CO₂ emissions.

MAN has invested around $257 million USD in the production of the new engine, for which up to 160 highly qualified employees will work in three-shift operations. The technical capacity allows for the production of approximately 50,000 engines per year.

The actual production volume is based on demand. Whether it is fully utilized ultimately depends on the customers.

Marco Singer, Process planner, MAN

In recent years, they have been somewhat reserved. As in the passenger car sector, discussions about the transition to electric drive have also caused uncertainty in commercial vehicles. Production ramp-up will initially operate in a single shift.

MAN has been working with Mapal for decades. When tenders were issued at the start of the D30 project in 2019, the Aalen-based tool manufacturer once again won the contract for the fine machining of the valve guide and valve seat pilot bore. The many years of shared experience contributed to this, as did a recommendation from the machine manufacturer Grob, which is responsible for the entire process and thus also for tool design.

The six cylinders of the engine each have two intake and exhaust valves, meaning 24 bores need to be made in the cylinder head bank. Since the diameters of the intake and exhaust vary, tools of different sizes are required for their machining. The machining takes place on a twin-spindle machine. It is integrated into a linked system with individual machines from Grob, which are loaded via linear gantries.

Stable Process Through Proven Technology

In the early phase of the project, another tool manufacturer was also entrusted with the fine machining. However, since their tools failed to deliver a stable and economical process, MAN ultimately focused entirely on collaboration with Mapal again. The company from Aalen initially entered the race with the fine machining system that had been running on many machines in two production halls at MAN for years. In close coordination with the customer, the partners further developed the system and achieved significant progress.

Singer acknowledges the achievements: "The machining process had fundamentally changed. For example, we eliminated a semi-cut and were able to dispense with pilot reaming. Instead, we only used the indexable insert tool on our pre-machined diameters, ensured a good bore entry for the reamer, and ultimately reamed through in one pass. Based on the experience, the process was optimized as best as possible."

The manufacturing concept achieved both good machining quality and the specified cycle time of approximately five minutes in total for the finishing of the valve seat and valve guide, ensuring the desired stable and economical process. "And this, despite the fact that the new engine increased the quality requirements in manufacturing," emphasizes Markus Meyer, who works closely with MAN as a technical consultant for Mapal.

For the valve and the two valve seat pilot bores, the tolerances are less than 20 micrometers (0.00079 inches). A precision of around 50 micrometers (0.0020 inches) must be maintained between the seat and the guide. There must be no misalignment between the valve seat and valve guide that could lead to unwanted shear forces. The required surface quality is an Rz of less than 20 micrometers (0.00079 inches). The cylinder head bank is made of GJV 450 cast iron, into which more wear-resistant materials in the form of a ring and a guide are pressed for the valves.

Modern Technology Further Reduces Unit Costs

A series of joint workshops focused on further optimizations, particularly regarding unit costs. These were to be further reduced before the start of series production, and through collaborative, professional teamwork, Mapal and MAN were able to achieve significant improvements.

The simplification of tool handling—specifically the reduction of setup time and thus an easier process for the operator—proved to be a lever for lower cost per part. Mapal introduced its EA system (EasyAdjust) for this purpose, which was implemented in the valve seat tool. In this system, the taper of the cutting edge is already integrated into the cassette that serves as the holder for the cutting insert. This eliminates the setup process for tapering the secondary cutting edge entirely, leaving only the diameter to be adjusted.

The operator no longer has to monitor two dial gauges. They focus on just one dial gauge to adjust the cutting edge protrusion relative to the guide pads. This is significantly faster.

Thomas Teuber, Head of Product and Application Management Fine Drilling at Mapal

The EA system also brings an improvement in the cutting edges: the TEC indexable inserts used in the EA system feature four cutting edges, twice as many as a conventional Mapal reaming insert. An optimized cutting material and an innovative coating increase the service life, ensuring an even more stable process.

The modifications had an effect: compared to the original machining concept, the costs for machining the valve seat and valve guide were reduced by around 40 percent. "I am very satisfied with the milestone achieved," says Marco Singer, explicitly praising the competent collaboration with Mapal. The ambitious process planner intends to continue driving the continuous improvement process forward.

MAN assumes that the D30 will be the company's last fully newly developed diesel commercial vehicle engine—after more than 100 years of diesel engine production at the Nuremberg site. By 2030, every second vehicle delivered to customers is expected to have an emission-free drive.

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