Aluminum Machining In New Dimensions

High volume milling cutter from MAPAL at bavius

On its new high-end model HBZ AeroCell 160, the machine tool manufacturer bavius ​​was able to achieve impressive metal removal rates of over 20 liters per minute with a new generation of aluminum high-volume milling cutters from the tool manufacturer MAPAL. The result of this successful collaboration comes at the right time for the aircraft industry: it is getting started again after the Corona dip.

The machine manufacturer, which emerged from the Handtmann Group, has been operating as an independent company under the name bavius ​​technologie gmbh since a management buyout in 2017 and is based in Baienfurt, Upper Swabia. Despite all the innovations, the business area has remained the same for almost four decades. CNC machining centers are designed and built for the precise, high-speed machining of large-format aluminum workpieces.

“Over 80 percent of our work is for the aerospace industry, where our AeroCell machines primarily produce large structural components,” explains Amit Paranjape, Sales Manager at bavius. Customers are aircraft manufacturers and their first and second supply chains. In order to fully utilize the bavius ​​systems, large volumes are required. Two different machine lines currently come from Baienfurt. Seat rails for aircraft, among other things, are processed on the PBZ profile processing centers. The HBZ horizontal machining centers are used to produce large structural components from solid material. “Here we machine everything that is long and wide,” explains Paranjape. “On our machines, users can process all the parts required for the framework of an aircraft.” The metal removal rates are extreme, as the example of a bavius ​​customer shows, who milled finished parts out of blanks weighing 1.3 tons into only 35 Weigh kilograms.

The trend is towards horizontal processing
The aircraft industry is currently undergoing a change in machine concepts. After decades of working on gantry machines or vertical machining centers, new investments now prefer horizontal machines in which the components are clamped upright and the spindle is brought in horizontally. The main advantage of the horizontal structure is the easier removal of the large amount of chips, which practically fall into the chip conveyor by themselves.

At bavius ​​you can clearly see that the aviation industry will soon overcome the corona crisis. Passenger numbers have already returned to pre-pandemic levels and are continuing to rise. Accordingly, new aircraft are needed again, which fills the order books of machine manufacturers. The demand from Germany, France, Spain and other countries shows that a lot of investments are being made in Europe again. What is particularly in demand are dynamic machines with high spindle performance.

bavius ​​is currently expanding its high-end HBZ AeroCell series with the new AeroCell 160. With a series of mechanical changes, the manufacturer is also achieving even greater dynamics with the new machine. Modifications in automation shorten non-productive times. It no longer works with hydraulic arms, but is electrically powered. With the setup station in front of the machine, a complete pallet change takes two to three minutes. If the pallet with the component is already docked, it takes less than a minute. The tool change has also been optimized, with a chip-to-chip time of 12 seconds now being achieved.

To the limit and further
The AeroCell 160 is designed for the highest machining rates in aluminum. A powerful coolant jet and a widened chip conveyor ensure that chip deposits cannot accumulate anywhere. “With our concept we avoid problems that occur with gantry machines. This allows us to optimally use modern tools,” explains Stefan Diem, application engineer at bavius. In order to test new machines and at the same time provide customers with references, bavius ​​carries out milling tests that go to the limit and beyond. “Many customers want to see proof before they buy a machine,” reveals Diem.

It is important for the machine manufacturer to use the currently most powerful tools for the tests, which are then also available for customer demonstrations. bavius ​​regularly tests tools from different manufacturers. Because of the tight production deadlines, there aren't many options for this. “In order to save time, a good exchange with the tool manufacturer is important for us,” says Stefan Diem. “We have had good contact with MAPAL for many years and have always been very satisfied with the roughing and finishing tools. I appreciate the good cooperation with MAPAL and feel well advised and in good hands.”

Because milling cutters from the OptiMill SPM series had already been used at bavius ​​and performed very well, MAPAL was asked again. The timing was right: With the OptiMill-Alu-Wave, the tool manufacturer had just finished developing a further development of its solid carbide roughing cutter and also offered the new aluminum high-volume cutter NeoMill-Alu-QBig with indexable inserts for larger diameters.

The milling tests are simple in structure, but place the highest demands on the tools. To do this, bavius ​​mills a series of full grooves into a large aluminum plate. Stefan Diem takes a very pragmatic approach: “If the tool creates the full groove, we can also use it to mill pockets and do any other processing.” This means that the cutting values ​​determined can be directly transferred to customer components.

The tool could do even more
For the tests with the OptiMill-Alu-Wave, bavius ​​chose the largest diameter of this three-edged milling cutter at 25 mm. At a spindle speed of 25,465 rpm and a cutting speed of 2,000 m/min, the spindle performance was gradually increased. Slot number 6 delivered the best metal removal rate with a record-breaking 20 dm3/min. This test run was carried out with a spindle power of 175 kW, with a torque of 66 Nm and an infeed of 30 mm. When attempts were made with higher powers, the machine stopped. “The tool can be fully extended, the limiting factor is the spindle,” says Diem, commenting on the result. “With the 25 mm OptiMill-Alu-Wave, we have reached a new dimension in aluminum machining. The cutter is definitely better than anything we’ve used before.”

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 an imbalance,” explains Tim Rohmer, Product Manager Solid Carbide Milling Tools at MAPAL. A Weldon surface, which is often attached to such tools as a pull-out protection, is the wrong solution here. In order to ensure that the machine runs smoothly, there is no way around careful balancing, even with symmetrical tools.

During the tests in Baienfurt, they were also very satisfied with the surface quality achieved. The cord geometry of the OptiMill-Alu-Wave ensures optimal chip formation. The polished groove profile ensures smooth removal of chips, which is supported by the central cooling of the tool in conjunction with the external cooling in the machine.

In further tests, pockets were milled into the aluminum plate, achieving a metal removal rate of 16 liters with very good surfaces. For application engineer Thomas Jungbeck and component manager Alexander Follenweider, who accompanied the tests for MAPAL, this is proof of the very good dynamics of the bavius ​​machining center: “Other machines often stop in the corners and cause high vibrations. This doesn’t happen at all with the AeroCell, which goes around corners almost without braking.”

The tests with the new NeoMill-Alu-QBig indexable insert tool from MAPAL at bavius ​​were also extremely positive, for which a diameter of 50 mm was chosen. The aluminum high-volume milling cutter achieved a metal removal rate of 18.4 dm3/min. On the machine, the milling cutter impressed with its high stability and smooth running and low cutting forces. For use at speeds of up to 35,000 rpm, MAPAL has provided the base body with four threaded holes for fine balancing. The highly precisely circumferentially ground indexable inserts achieve surface qualities of Ra 0.8 µm and Rz 4 µm during pre- and finish machining. They have a polished chip breaker to reduce frictional resistance and heat development. Weight was also saved to reduce centrifugal forces. “For larger diameters, cutters with indexable inserts are the more economical solution,” says Heiko Rup, product manager for tools with indexable inserts, when comparing them to solid carbide cutters.

With a diameter of 25 mm, the two systems merge into one another. “Some of our customers always choose the more cost-effective indexable inserts whenever possible, others prefer to save themselves an additional work step and continue with the solid carbide milling cutter,” reports Stefan Diem. With different possible radii of its tools, MAPAL gives users flexibility.

With the AeroCell 160 horizontal machining center and the aluminum high-volume tools, bavius ​​and MAPAL offer users a combination that takes the machining of structural components to a new level.