Low-vibration milling


CNC service provider Rathmann saw room for improvement when it came to face milling large pump housings made from cast materials. During tests with the KOMET® hi.aeQ arbor face-milling cutter, the tool life was doubled and feed values were vastly improved in comparison with the predecessor tool. These results have turned into practical success over the past year.

Werner Rathmann Maschinenbau GmbH, which was founded in 1960 and has headquarters in Ritterhude, near Bremen, has grown from a small business into a medium-sized company concerned with the production of steering gear for the maritime industry. Steelwork continues to be an important element in the construction of these products. Operations manager Thomas Medrow explains, "Today we are able to produce large steering gear from scratch with a total weight of up to 68 tons, which includes steelwork, mechanical machining, blasting and paintwork, right up to final assembly and the delivery of ready-to-install components." A considerable range of services for a company that currently only has 65 employees.

The thing that has become the most economically important, however, is mechanical production. As an experienced CNC service provider, Rathmann is in high demand, particularly as a contract manufacturer for large and complex components. Everyday operations for the multifunctional machinery include, for example, the precise machining of components for large-volume high-pressure pumps used in the offshore and chemical industries and ultrahigh vacuum housings for analytical equipment.

Machining operations at Werner Rathmann GmbH consist of 80% milling and 20% turning. Among other equipment, three multi-axis, automated multifunctional machining centres are used for high-performance and, if necessary, high-precision turning. The milling area contains four machining centres with a pallet changing system, which enables components to be machined from five sides and, if necessary, on five axes at the same time.

The large-scale machines are of particular importance. Rathmann has only recently invested in a lathe with a turning length of ten metres and a maximum turning diameter of 1600 mm. The milling department will also have access to new equipment this year; the team is already looking for a boring machine that also has an X-travel path of ten metres. "You wouldn't expect to see that when you enter our small site in Ritterhude, would you?" smiles Thomas Medrow. "On our large-scale machines we can machine components weighing up to 25 tons, special materials such as anti-magnetic submarine steel as well as other materials used in the field of supra alloys."

Even the peripheral equipment is impressive: The production planning team creates all machining programmes using volume models and transfers these online to the machines. At the same time, the selected tools are mounted and measured with µm accuracy on a state-of-the-art adjustment and measuring device, and tested for plausibility. This data is in turn transferred to the machines via the network.

KOMET GROUP – a strong partner for high-quality tool engineering
When it comes to tools, Rathmann has been working in close partnership with the KOMET GROUP, one of the leading single-source suppliers of precision tools, for many years. Thomas Medrow recalls, "When I started working here 25 years ago, KOMET® tools were already part of the standard equipment. The ABS® tool clamping and coupling system, for example, was already being used, and it is still helping to make our machining processes as cost-effective as possible today."

A quick look inside the tool magazine shows that many different tools from the KOMET GROUP are used in mechanical production – from the ABS® holders, extensions and reduction pieces to the KOMET MicroKom® hi.flex, MicroKom® M04 digital and M03Speed precision adjustment heads, the TwinKom® double cutter, the KUB Trigon® and KUB Centron® indexable insert borers as well as the KUB® V464 core bits. "We also use KOMET® solid carbide drills and milling cutters, JEL® thread mills and DIHART® reamers," confirms the operations manager.

The latest tool from the KOMET GROUP to be used in Ritterhude is the KOMET® hi.aeQ arbor face-milling cutter. After being successfully tested on a Butler CNC machining centre, it has been used virtually every day for a year on a Mazak machining centre to machine pump housings with guaranteed process reliability. The grey cast iron parts, which measure around 1000 x 1000 x 400 mm, need to be faced-milled on at least three sides to enable further components to be attached.

Heiko Fischer, responsible for technical consultation and sales for KOMET GROUP GmbH in Lower Saxony, recommended the KOMET® hi.aeQ face-milling cutter with a diameter of 160 mm for this task. The basic body of the arbor milling cutter is equipped with a total of 20 tangentially screwed Q80 indexable inserts, which are alternately arranged vertically and horizontally at the circumference of the tool. The objective was to achieve improved cost-effectiveness in comparison with the predecessor tool that was equipped with ceramic inserts, i.e. a longer tool life and shorter machining time. "Low-vibration running was a decisive factor," explains machining expert Fischer. "Since the housings are relatively thin-walled in relation to their size, with a wall thickness of just 25 mm, this was a real challenge."

KOMET® milling cutter impresses with improved cutting data and lower indexable insert consumption
KOMET application engineer Thomas Hess also offered support in determining the ideal cutting data: "We performed various tests, wet and dry, and found that the best results were achieved with dry machining. We were able to achieve a tool life of 520 m at a cutting speed of vc = 360 m/min and a feed rate of 3.0 mm per rotation. This corresponds to a feed per tooth of fz = 0.15 mm/tooth. The working depth in this case was ap = 1.5 mm." These figures are impressive, especially considering there is still room for improvement, as Thomas Medrow explains, "The Mazak machine is already around 20 years old. This was something we had to consider when it came to the cutting data."

This success has largely been due to the carbide indexable inserts, which feature eight usable cutting edges. They were originally designed for counterboring operations and are ideally suited to milling. They have a special coating and guarantee a high level of stability and cutting performance. This makes the tool and component less likely to vibrate, even during high-speed milling.

Thomas Medrow is impressed by the KOMET® hi.aeQ face-milling cutter: "My colleagues working with the machine confirm the test results day after day. With the same machining parameters in terms of feed rate and speed, we can achieve double the tool life per cutting edge in comparison with the previous ceramic milling cutter. But we can also achieve a considerably higher effective feed rate and therefore shorter machining times. The eight usable cutting edges per indexable insert have also generated further economic advantages during the machining process. And most important of all, the milling cutter runs with absolute process reliability."

Cast iron machining has its difficulties, such as cavities and inclusions. The KOMET® hi.aeQ milling cutter can handle this, however, without any major problems. Heiko Fischer explains, "I essentially put this down to the tangential insert principle. If there's a problem with the cast iron, a small piece may break off at the front of the cutting edge. This does not generally reach the insert seat, however. With highly positive cutting edges, on the other hand, the entire insert is often destroyed when it moves into a cavity. This means that the insert seat and therefore the milling cutter need to be repaired or taken out of use completely."

At Rathmann, the inserts are changed over during the tool setup stage. According to machine operators, "With the KOMET® hi.aeQ face-milling cutter, it is much easier to change inserts than with comparable tools from other providers. The clamping screw is released, the insert is turned and the screw is tightened again. It is not necessary to adjust the height, as the 20 inserts have a total maximum offset of 2/100 to 3/100 mm." This means that a surface finish of up to Ra=0.6 µm can be achieved when machining grey cast iron. "Even with spheroidal graphite cast iron EN-GJS-600-3, we can still achieve an Ra value of 0.8 to 1 µm," explains application engineer Hess.

If even higher surface requirements need to be met, KOMET consultant Heiko Fischer can help with special concepts: "This milling cutter also comes with the option of precision insert seat adjustment, whereby the user can adjust each individual indexable insert with a high degree of accuracy." For the KOMET® hi.aeQ face-milling cutter there are now also indexable inserts that are designed for machining steel. The range of milling cutters offered by the KOMET GROUP is growing continuously on the whole, as can be seen in the new "KomPass Milling" milling cutter catalogue.  

The arbor face-milling cutter in a class of its own

The KOMET® hi.aeQ high-performance arbor face-milling cutter is the ideal tool for the reliable shoulder and face milling of cast materials. The chemically nickel-plated basic body of the arbor milling cutter is equipped with tangentially screwed Q80 indexable inserts, each with eight usable cutting edges. They are alternately arranged vertically and horizontally at the circumference of the tool and guarantee a high level of stability. They are characterised by low cutting forces, which in turn means reduced power consumption. The low-vibration, steady milling characteristics also reduce the load on the spindle. This concept guarantees a particularly high level of process reliability, when combined with modern substrates and coatings which are matched to the particular machining task. The indexable inserts can be supplied with a PVD or CVD coating. The KOMET® hi.aeQ arbor face-milling cutter is available with diameters of 40, 50, 63, 80, 100, 125 and 160 mm.

Metal machining at the cutting edge of technology

Since it was founded in 1960, Werner Rathmann Maschinenbau GmbH has focussed on the manufacture, machining and repair of particularly challenging components in the fields of steelwork and CNC metal machining and metalworking. This is not limited to the conceptual formulation of individual production steps, but also applies to the creation of complex systems that combine steelwork and mechanical further processing. Machining ranges from steel products to aluminium, stainless steel and anti-magnetic stainless steel.


Werner Rathmann Maschinenbau GmbH
Deltastraße 3 D-27721 Ritterhude, Germany
Tel.: 04292-8124-0
Fax: 04292-8124-70

Press contact

Trade press:

Wolfgang Klingauf

+49 (0) 821.524693