Kennametal Dodeka Milling Cutter Significantly Increases Productivity for Komatsu Mining Company

Problem:
It tops the list as the world's largest hydraulic excavators. Since its market launch in 1986, more than 60 have been sold. And no wonder, given the mighty attributes of the Komatsu PC8000 front shovel excavator. Weighing 720t and with a power output of around 4000 bhp, this colossus can shift up to 42m3or 75t of bulk material in a single shovel load.

The PC 8000 is built by Komatsu Mining Germany (KMG), Komatsu's European production facility for heavy hydraulic excavators. Here, in Düsseldorf, the emphasis is on the development, manufacture, and marketing of large hydraulic excavators with working weights ranging from 250 t to 720 t and with shovel capacities from 15m3 to 42m3 respectively. In addition to concentrating on product quality, the corporation pays
particular attention to continuous process optimization. This can be seen in a current example, taking the form of a new surface milling system which has proved capable of increasing productivity and processing reliability at the same time.

“Komatsu's heavy hydraulic excavators are built here, in this factory,” emphasizes Hermann Führer, head of Heavy Machine Construction at KMG. “From the initial sheet metal processing to the finished machine, we make almost everything ourselves. Thus, we produce the supporting parts of the excavator, which can weigh anything from 1t to 75t.”
 
Steel fabrications of this type include so-called “caterpillar” mountings and the center sections of the machines. Two caterpillar mountings, on which the crawler chains will subsequently run, and a center section, on which the machine swivels, form the chassis of the vehicle. Produced as individual parts, these are subsequently assembled by means of flanges at the future place of use of the machine. This entails moving caterpillar mountings weighing 23t and the center section weighing as much as 42t. Recently, a Kennametal Dodeka surface milling cutter was put into service in Düsseldorf to process the flange faces of the caterpillar mountings and center section.

“With this tool,” Führer reports, “we machine areas of around 2 m2 in size.” When dry machining St52, processing depths of 15 mm are achieved. He does, however, emphasize that this presents a problem. “Since the individual parts of the structure are burned out of a single steel sheet, the caterpillar mounting parts have burnt edges. In the past, these were difficult to mill because they are harder than the adjoining material.” This was made even more difficult by the fact that large, heavy welded fabrications often prove to be unstable systems during machining.

Solution:
“This machining problem was known to us,” says Fabian Henkel, a field engineer with Kennametal, discussing these aspects. “As a result, I presented the Dodeka milling machine to Jörg Arndt, the Komatsu Tools Manager. He realized immediately that this tool should be considered not only for this purpose but for others as well.” Soon afterward, Henkel demonstrated Dodeka together with Dieter Graunitz, a colleague from Kennametal's Applications Engineering Department, in the presence of Jörg Arndt and Detlef Bier, a CNC programmer with KMG. First and foremost, it was a great success. “But we soon realized that, with the indexable insert we were using, we could not achieve the optimum result from the standpoint of the burnt edges,” reports Henkel. “With our
product specialist, Andreas Wessel, we developed a new shape which produced excellent results and which is still in use today.”
 
The results, according to Henkel, provide an excellent illustration of how a tool manufacturer and user can work together in an exemplary way. Henkel himself has now been servicing the Düsseldorf-based corporation for four years. Among other things, this means at least one visit a week to the KMG site. “In this way, I not only keep the customer informed of new developments at Kennametal but also arrange early meetings to discuss application related problems. With this setup, new projects come up time and again, the milling project being only one such instance,” explains Henkel. At all events, it is typical of this case that not only did the tests on the tool cover every minute detail, but that they also gave rise to findings contributing to its optimization. In particular, it proved possible to develop a chip shaping step for
heavy-duty machining with the milling cutter.

As Osny Fabricio, Product Manager with Kennametal, recalls looking back on the early days of the tool, “The fundamental objective of our development work was to bring a user-friendly, multipurpose, surface milling cutter to the market. The design which ultimately emerged is in marked contrast to what one usually imagines a steel milling cutter to look like. Normally, people think of a positive arrangement for the inserts. In the case of the Dodeka milling cutter, all the cutters are arranged negatively, both axially and radially. “In combination with the indexable inserts, the geometry of the
milling cutter permits a very soft cut.
 
“For manufacturing operations, we recommend cutting depths up to 4.5mm and feed rates up to 0.6mm per tooth while, with slightly reduced cutting depths, feed rates can be increased to 0.8mm per tooth,” says Fabricio. Depending on the material concerned, cutting rates can reach up to 400m/min. Moreover, the tool, featuring 12-edged indexable inserts, is extremely economical. “Initially, we developed the milling cutter for certain customers as a special tool,” says Fabricio, “but it soon became clear that there was a far-reaching demand for this particular design. As a result, we eventually developed it further so that it became a standard product. “Following this additional development, the tool was tested in 84 corporations throughout the world. “The evaluation of the field tests
was particularly important for us,” emphasizes Fabricio. “The reason is revealed in the heavy-duty machining chipbreaker of our insert, which was developed in association with Komatsu. “Today, the milling cutter stands out as an all-round design with which machining operations can be carried out on numerous types of material. These range from steel and stainless steel to inconel, titanium and cast iron. As a result, the user has an exceptionally soft cutting tool at his disposal which can also be used under unstable conditions.

Results:
Since the introduction of the Dodeka milling cutter, the people at KMG have come a long way. “To date, we have already milled a number of caterpillar mountings,” reports Führer on the current state of affairs. “Accordingly, we have adequately tested this particular application. As we have also succeeded in machining the center section satisfactorily, we are now trying to extend our experience to other processes.” Thus, the intention is al-
so to machine excavators' drive wheels with the Dodeka tool in the future. The casting allowances on cast parts must be milled off, which in turn means a high proportion of metal removal, as machining depths of 60-70mm must be achieved. “Since, in the case of castings, a considerably harder material must be milled than that used for caterpillar mountings or center sections. We are in the process of further developments, enhancing the Dodeka range to achieve even greater results on machining traditionally challenging processes.” Arndt admits. In addition to this application, it is also intended to machine the supporting surfaces of the excavator ring mount with the Dodeka milling cutter in the future. In this case, the milling process must encompass circles up to four meters in diameter.

Meanwhile, how far have they got with extending the use of the Dodeka tool? In Arndt's opinion, it has already been introduced in areas amounting to one-third of the planned applications. As regards the extent of the spectrum of uses, the successes achieved so far with milling the center sections and caterpillar mountings speak volumes.” Today, we are operating at the same cutting rate as before but, due to the unique Dodeka design we were able to increase the depth of cut from 3 mm to 4mm,” reports Bier. Since the cutter has two more tool inserts than the cutter previously used, it can be operated at a feed rate of4.8mm per revolution. Previously, it was 3mm. “In this way, we not only make savings of 20% on machining operations,” Bier sums up, “but we have also been able to increase the volume of machined metal and roughly double the service life of the cutting edges.”
 
At present, one-third of the milling applications planned by KMG have been covered by tests. By the end of the year, the outstanding applications should also have been finally tested. Führer estimates that they will realize considerable cost savings and substantial productivity improvements in the production cycle. In addition Bier emphasizes that there will also be enhanced process reliability and security. For Kennametal, the project has proved to be an important building block in making a standard tool out of a special tool.

“Today, in the Dodeka concept, we have not only produced an outstanding product in the field of milling cutters,” says Fabricio, “but, in particular, have also taken an important step toward establishing our image as specialists in milling tools.”

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