Komet has latetly begun using the plunge milling technique and its own Quatron hi.feed indexable insert milling cutter to carry out roughing of the housing for the PKE (facing head with single slide). This has enabled the machining time to be reduced by approximately 60 percent.
The KomDrive mechanical draw bar tools from KOMET are looked for after for all applications involving large-scale series manufacturing and requiring high productivity, whether on transfer lines or in special purpose machines and automatic rotary indexing machines. These tools include the PKE single-slide facing heads. Thanks to their large clamping surfaces, these ensure that the tool is securely fastened and enable heavy cutting applications in a low speed range. To guarantee high accuracy over the long term, the manufacturing of these facing heads needs to be extremely precise.
This is carried out at the headquarters of the KOMET GROUP in Besigheim, where all sizes – with diameters from 80 mm to 250 mm and special designs with diameters of up to 500 mm – are produced. In order to optimise production in terms of costs, Project Engineer Christoph Seybold decided to work together with the experts responsible for soft machining of housings and slides: “Our primary focus was on the tools and machining processes used for machining the slide chamber and slide.” This decision was made because these details are particularly important for ensuring that the facing head functions reliably down the line.
They selected the PKE 125 series, which at the time was being manufactured in large quantities, for their optimisation experiments. With this variant, the slide chamber in the housing is a groove with a width of 62 mm, a length of 140 mm and a depth of 30 mm. In order to ensure that the slide can move in this groove without play, both components must be ground following hardening so that they fit together precisely.
However, soft machining alone is extremely demanding, as Programmer Markus Kühnl explains: “We use a nitrided steel for these parts, which is exceptionally tough and extremely abrasive. This results in extremely short tool life for the milling cutters, particularly when machining large volumes.”
The slide chambers were originally manufactured using shell end face milling cutters made of HSS. The team then experimented with a variety of coatings and with various indexable insert and solid carbide tools – including some tools manufactured by competitors.
As an alternative, the machining specialists tested the idea of using a different roughing method, namely plunge milling. However, the initial results of these tests were also unsatisfactory. The indexable inserts of the plunge milling cutters that were initially used did not even last for machining a single component.
The team kept up its efforts to achieve an optimised roughing process: “In the meantime, KOMET developed its own comprehensive milling cutter range with indexable inserts, incorporating a great deal of experience gained in the field of drilling. This range also includes the KOMET Quatron hi.feed screw-in cutter, which was developed on the basis of our KUB Quatron solid drill range. This tool is also well-suited to machining using plunge milling, which is why we decided to run new experiments with that method using this new tool.” The experts selected the 42 mm version of the milling cutter for the housing groove. Its five insert seats were fitted with the Quatron W8332 indexable inserts, which had already been used successfully for drilling applications, as the requirements for the plunge milling process are similar to those for drilling.
“It was beneficial to us that KOMET recently began offering indexable inserts with special coatings for nitrided steel,” explains Walter Sibla, an experienced programmer responsible for, among other things, the DMG Mori NT 4250 SZ turning/milling centre, which is used in machining housings. The first tests alone were more successful than any previous machining attempt. Walter Sibla now uses the Quatron hi.feed for series machining of the housings. His reasons for doing so: “This KOMET milling cutter enables us to carry out plunge milling at a cutting speed of 62 m/min and a feed rate of 0.5 mm/rotation. It also enables us to achieve a tool life of approximately 2.5 m per cutting edge. That doesn’t sound like much, but it is the best result possible by far when working in this difficult material.”
Project Engineer Christoph Seybold is also satisfied: “We have been able to reduce the machining time by approximately 60 percent in comparison to the previous roughing method.” He considers the new Quatron hi.feed indexable insert milling cutter to be a particularly important factor in this improvement: “If we can use tools manufactured in-house at KOMET, we do so, because we are certain of the quality of our own tools. The Quatron hi.feed has also proven that it is superior to similar milling cutters from other suppliers. It certainly saves us time and money in this application.”
For the subsequent finishing process, the KOMET F.line HPC solid carbide milling cutter is used, which contributes to ensuring optimum cost-effectiveness thanks to its cutting performance (vc=96 m/min, vf=0.3 mm/rotation in the nitrided steel mentioned above). This tool has also proven to be effective for manufacturing the PKE 125 operating slide, offering a further benefit for housing machining. The KOMET Quatron hi.feed indexable insert milling cutter and KOMET F.line HPC milling cutter are considered to be standard tools for machining the PKE 125 operating slide.
For more information visit: www.kometgroup.com