04.12.2023
Aluminium machining in new dimensions
MAPAL high-volume milling cutters in use at bavius
The machine tool manufacturer bavius technologie gmbh was able to achieve impressive material removal rates of over 20 litres per minute on its new high-end model HBZ AeroCell 160 with a new generation of aluminium high-volume milling cutters from the tool manufacturer MAPAL. The result of this successful collaboration comes at the right time for the aerospace industry, which is taking off again following the downturn caused by coronavirus.
Trend geht zu horizontaler Bearbeitung
Bei den Maschinenkonzepten vollzieht die Flugzeugindustrie gerade einen Wandel. Nachdem jahrzehntelang vorzugsweise auf Gantry-Maschinen oder vertikalen Bearbeitungszentren gearbeitet wurde, werden jetzt bei Neuinvestitionen horizontale Maschinen bevorzugt, bei denen die Bauteile hochkant aufgespannt sind und die Spindel horizontal herangeführt wird. Für den horizontalen Aufbau spricht vor allem die leichtere Abfuhr der großen Menge an Spänen, die hier praktisch von selbst in den Späneförderer fallen.
Bei bavius merkt man deutlich, dass die Luftfahrtbranche die Coronakrise bald überwunden hat. Die Passagierzahlen haben bereits wieder das Niveau vor der Pandemie erreicht und steigen weiter. Entsprechend werden auch wieder neue Flugzeuge gebraucht, was Maschinenherstellern die Auftragsbücher füllt. Die Nachfrage aus Deutschland, Frankreich, Spanien und weiteren Ländern zeigt, dass auch in Europa wieder viel investiert wird. Gefragt sind vor allem dynamische Maschinen mit hohen Spindelleistungen.
Bis ans Limit und weiter
Weil Fräser der OptiMill-SPM-Reihe zuvor schon bei bavius im Einsatz waren und dabei sehr gut performten, wurde MAPAL erneut angefragt. Das Timing passte: Mit dem OptiMill-Alu-Wave hatte der Werkzeughersteller gerade eine Weiterentwicklung seines VHM-Schruppfräsers fertig entwickelt und bot zudem für größere Durchmesser den neuen Alu-Hochvolumenfräser NeoMill-Alu-QBig mit Wendeschneidplatten.
Die Fräsversuche sind im Aufbau einfach gehalten, stellen jedoch an die Werkzeuge höchste Anforderungen. bavius fräst dazu eine Reihe von Vollnuten in eine große Aluminiumplatte. Stefan Diem verfolgt damit einen sehr pragmatischen Ansatz: „Wenn das Werkzeug die Vollnut schafft, können wir damit auch Taschen fräsen und jede andere Bearbeitung machen.“ So sind die ermittelten Schnittwerte direkt auf Kundenbauteile übertragbar.
The tool could do even more
For the tests with the OptiMill-Alu-Wave, bavius chose the largest diameter of this three-fluted cutter at 25 mm. At a spindle speed of 25,465 rpm and a cutting speed of 2,000 m/min, the spindle power was gradually increased. Slot number 6 delivered the best material removal rate with a record-breaking 20 dm3/min. This test run was performed with a spindle power of 175 kW, with a torque of 66 Nm, and a material removal rate of 30 mm. The machine stopped during tests at higher powers. “The tool can be fully deployed, the limiting factor is the spindle”, Diem comments on the result. “With the 25 mm OptiMill-Alu-Wave, we have achieved a new dimension in aluminium machining. The milling cutter is definitely better than anything we had previously used.”
bavius used the Safe-LockTM system as pull-out protection. “In this speed range, symmetrical pull-out protection is very important in order not to create imbalance”, explains Tim Rohmer, Product Manager Solid Carbide Milling Tools at MAPAL. A Weldon flat, which is often attached to such tools as pull-out protection, is the wrong solution here. To guarantee the smooth running of the machine, there is no way around careful balancing, even with symmetrical tools.
The tests in Baienfurt were also met with a great deal of satisfaction in terms of surface quality. The cord geometry of the OptiMill-Alu-Wave ensures optimum chip formation. The polished groove profile ensures seamless chip removal, which is supported by the central cooling of the tool in cooperation with the external cooling in the machine.
In further tests, pockets were milled into the aluminium plate, with a material removal rate of 16 litres still being achieved with very good surfaces. For Application Engineer Thomas Jungbeck and Component Manager Alexander Follenweider, who monitored the tests for MAPAL, this is proof of the very good dynamics of the bavius machining centre: “Other machines often stop in the corners and cause high vibrations. This doesn’t occur at all with the AeroCell, which goes round corners almost unrestrained.”
The tests at bavius with the new indexable insert tool NeoMill-Alu-QBig from MAPAL, for which the 50 mm diameter was selected, were also extremely positive. The aluminium high-volume milling cutter achieved a material removal rate of 18.4 dm3/min. On the machine, the milling cutter stood out with its high level of stability, smooth running and low cutting forces. For use at spindle speeds up to 35,000 rpm, MAPAL fitted the tool body with four threaded bores for fine balancing. The high-precision peripherally ground indexable inserts achieve surface finishes of Ra 0.8 µm and Rz 4 µm during rough and fine machining. They are equipped with a polished chip guiding stage to reduce frictional resistance and heat release. Weight was also saved in order to reduce centrifugal forces. “For larger diameters, milling cutters with indexable inserts are the more economical solution”, explains Heiko Pup, Product Manager for tools with indexable inserts, contrasting the NeoMill-Alu-QBig milling cutters with solid carbide milling cutters.
With a 25 mm diameter, the two systems merge. “Some of our customers always go for the more cost-efficient indexable inserts if possible, others prefer to save themselves an extra machining step and continue with the solid carbide milling cutter”, explains Stefan Diem. With different possible radii for its tools, MAPAL provides users with flexibility.
With the horizontal machining centre AeroCell 160 and the aluminium high-volume tools, bavius and MAPAL provide users with a combination that takes machining structural parts to a whole new level.
Contact
Kathrin Rehor Public Relations Kathrin.Rehor@mapal.com Phone: +49 7361 585 3342