Strategic aircraft component with all the features In Ten Hours From One Ton to 71 kg

Related Vendors

Fastems Systems GmbH

item Industrietechnik GmbH

In a joint project, Mapal and the machine manufacturer Bavius developed and produced a prototype component for the aviation industry. 

The roughly three by one meter aluminum component is modeled after a real rear spar from aircraft construction but has also been enhanced with numerous additional demanding applications. Alongside its complexity, the short machining time of ten hours is impressive, achieved through the productivity of the "Bavius AeroCell" and the specialised tools for aluminum machining from Mapal.

Bavius Technologie GmbH in Baienfurt (Germany) has specialised in high-speed volume machining of structural aluminum components, typically required in aerospace for wings and fuselage.

Components for satellites and rockets like the Ariane 6

Bavius (formerly Handtmann A-Punkt Automation) has been operating as an independent, family-run company since 2017 and focuses on two product lines: Profile machining centers (PBZ) and horizontal machining centers (HBZ) with the "AeroCell" series.

Gallery

Gallery with 9 images

With approximately 120 employees, Bavius generates more than 80 percent of its revenue in the aerospace industry. As OEMs or suppliers, their customers manufacture components for commercial and military applications. Components for satellites or rockets like the Ariane 6 are also produced on the machines.

Everything made in Germany

Most of Bavius' machines are located in Europe, with other strong markets being North America and Asia. In the USA, the machine manufacturer operates its own subsidiary, but production for the global market takes place exclusively in Baienfurt, in two air-conditioned halls with a production area of around 10,000 square meters (approx. 107,600 sq ft).

140 kW spindle power and 30,000 rpm

A key strength of Bavius' five-axis machining centers is their exceptional dynamics, enabling high productivity during high-speed machining. To extract the maximum performance from the machines, Bavius manufactures its milling heads in-house. The flagship of the product line is the Bavius "AeroCell 160 I 400," featuring a spindle power of 140 kW and a maximum speed of 30,000 revolutions per minute. The 140 kW is already achieved at 18,000 revolutions, meaning the maximum power is available over a wide speed range.

"When we do something, we want to do it excellently, and with our 'AeroCell 160 | 400,' we are technologically leading worldwide," assures Dominik Merz, Director Global Sales at Bavius.

1 ton raw part—71 kg finished part

The rear spar was chosen as the prototype component because it fits perfectly on the machine, with its 1.6-meter table height and 4-meter width (approx. 13 ft). This rear spar is a typical structural component in the wings. Ribs run between the rear spar and the front spar, arranged perpendicular to the spars. The structural components define the geometry of the wing, with the outer skin riveted onto them. The finished component, made of aircraft-grade aluminum 7075, measures exactly 2977 x 748 mm (approx. 117 x 30 inches). Typical for aircraft parts is its flat shape, with a height of 138 mm (approx. 5 inches). From an initial weight of just over one ton, only 70.61 kg remains after machining—a ratio that is also common in the aerospace sector.

Variety of different applications integrated

For legal reasons alone, Bavius and Mapal could not use a real component from an aircraft manufacturer for machining. However, this simultaneously gave the team the freedom to use the design for a variety of other applications.

This demonstration object is far more complex than any real rear spar and also includes applications that may not necessarily be associated with this component but could be required in other parts. "A customer familiar with structural components who sees our part will recognise it and find features that are also present in their own components," explains Dominik Merz regarding this approach.

Five-axis machining: Convex radius of 9.5 meters 

The machining took place in Baienfurt in two clamping operations. Setup 1 was performed with low-clamping tension, while in Setup 2, vacuum technology ensured a secure hold. At first glance, the front side looks simpler than it actually is. The surface is not flat but bends slightly convex over a radius of 9.5 m (approx. 30 ft).

This means the component cannot simply be plan-milled but requires five-axis machining. For roughing and finishing, Mapal used the "NeoMill-Alu-QBig" with a 50 mm (approx. 1 inch) diameter and the "OptiMill-Alu-Wave" with a 25 mm (approx. 0.9 inches) diameter. The surface finish was completed with a custom PCD milling cutter.

Pockets in all shapes

The machining of the backside was particularly challenging, as it is divided into nine different sections, each with specific applications.

Like every rear spar, the sample component features many pockets, but here designed in all conceivable shapes: rectangular, triangular, round, open, closed, some with slanted or curved bottoms. The ribs are very thin, and the walls are mostly slanted. The pockets are up to 137 mm (approx. 5 inches) deep.

After the preliminary machining by the "NeoMill-Alu-QBig," an "OptiMill-Alu-Wave" in various lengths was used for clearing the pockets. The semi-finishing was performed by a corner milling cutter specifically modified for aerospace applications. Thanks to its special geometry, the tool is particularly suitable for residual material machining in corners as well as for the subsequent finishing of floors and walls. The special core rise ensures optimal stability during the machining process. To efficiently machine all areas, the Mapal specialists used the modified corner milling cutter in various diameters and lengths.

Zigzag strategy in climb milling and conventional milling

As efficiency was also considered in Mapal's programming, Components Manager Alexander Follenweider explains: "We work with a zigzag strategy in climb milling and conventional milling to save travel paths. This means the strategy is constantly switched during machining."

Despite high machining speeds, the aluminum must not be damaged as it changes its properties when overheated.

425 kg of aluminum chips in 55 minutes

The "OptiMill-Alu-Wave" was operated at 29,000 revolutions, a cutting depth of 48 mm (approx. 1.9 inches), and a feed rate of 12 m/min (approx. 40 ft/min) at its peak. The larger "NeoMill-Alu-QBig" achieved a feed rate of over 25 m/min (approx. 80 ft/min) at a cutting depth of 10 mm (approx. 0.4 inches).

In the first 55 minutes of machining the second clamping alone, 425 kg of aluminum was machined, with a peak chip volume of more than 14 l/min. "These are excellent values that we were able to achieve here—and we also produced very good surfaces," praises Stefan Diem, application technician at Bavius, regarding the results.

Nothing is standard

The various pockets are not the only challenges of the component: The holes on four brackets are only accessible with an angled head. Undercuts are also required in other areas. A typical T-stiffener for structural components is also present on the sample part and is machined with a custom PCD tool.

Drilling and reaming operations are also required in certain areas. "Nothing about our component is normal," comments Dominik Merz on the fact that hardly any right angles can be found. Such slanted designs, however, are quite typical for the aerospace sector.

A component manufactured in ten hours

For customer presentations at the involved partners and as an eye-catcher at trade fairs, five of these rear spars were manufactured in Baienfurt. The machining of one part takes a total of exactly 10 hours, with which the project participants are highly satisfied. "On other machines, such a component typically takes 20 to 30 hours," estimates Merz.

Advantages of horizontal machining

Traditionally, structural components are machined on vertical gantry machines with large tools, typically cutter heads with diameters of 125 mm. Feed rates and speeds remain low. A disadvantage of this method is that chips can accumulate and cause scratches. Additionally, heat is introduced into the component. Horizontal machining eliminates these issues. Combined with high-performance tools that allow for high cutting values, the dynamic "AeroCell 160 I 400" with its extreme acceleration opens up entirely new possibilities.

Close collaboration

Mapal and Bavius have maintained a very intensive collaboration for many years, benefiting both sides. When Mapal developed the "NeoMill-Alu-QBig" and the "OptiMill-Alu-Wave," prototypes of the new tools were already tested and further optimised in Baienfurt.

Require tools that push the machine to its limits

The tool manufacturer in Aalen does not have similarly powerful machines itself. On the other hand, Bavius also relies on innovative tools, as Stefan Diem explains: "For our premium machine, we need top tools from a provider like Mapal with its high-volume milling cutters that push our machine to its limits. Universal tools don't work for this; we don't gain any insights from them."

Two years ago, the partners demonstrated what the "AeroCell 160" can do in collaboration. During test operations under overload, the solid carbide cutter "OptiMill-Alu-Wave" achieved a chip volume of up to 20 l/min in full slot milling in standard aluminum. The currently achieved peak value of 12 l/min on a component made from the more tensile AL 7075 is equally impressive.

"I greatly value the collaboration with Mapal because we communicate openly and fairly, and we always get a solution presented," emphasises Stefan Diem. For Jens Ilg, Business Development Aerospace & Composites at Mapal, the joint success also has a personal aspect: "I also gain an optimal understanding of our own products when I have used them under real, required conditions. And I can then offer them to a customer with the corresponding recommendations."

(böh)