HIGH PERFORMANCE IN PRECISION MACHINING OF ALUMINIUM
Lightweight components subject to particularly high dynamic loads, such as aluminium structural parts for aircraft, are usually machined from solid material. Up to 95 percent of the material is removed during the process. Such components are sometimes up to 30 metres long. The cutting machines need to deliver enormous performance with high precision because with residual wall thicknesses of less than two millimetres in some cases, even deviations in the tenths of a millimetre range could cause problems. Today, the market demands fully tested and optimised technology solutions consisting of machine, automation, tools and machining software. In this environment, milling tools which MAPAL has developed especially for high-performance machining have proven their worth.
PRECISION CHALLENGE
Aircraft structural parts are partly milled from solid rolled material as well as forged blanks, whereby the machining volume can reach up to 95 percent“, added Michael Hofmann, Area Sales Manager at MAPAL. The structures are as filigree and thin-walled as possible in order to save as much weight as possible. This
places the highest demands on precision, because during machining the tightrope walk between low weight on the one hand and assured compliance with the required component properties on the other must be mastered. In addition, the surface finish quality plays an essential role with safety-relevant components. Even the most minor damage could become the starting point for fatigue cracks in critical areas such as transitions or fillets. Such risks of failure must be avoided at all costs.
At the same time the fastest-possible machining rates are required from an economic point of view. The tools used therefore play an essential role in addition to the properties of the processing machine. Their suitability is put through its paces as part of extensive pre-testing, as the order depends on successful validation by the customer for all those involved. MAPAL is a frequently consulted development partner for such projects due to its expertise in tool development and manufacture.
EXTREME DEMANDS ON THE TOOLS
The demands on the tool are extremely high for a component currently in the pipeline“, said Thomas Jungbeck, Technical Advisor at MAPAL. The customer requires high cutting performance, for which the bavius machine (a PBZ HD with a spindle power of 80 kW at a spindle speed of up to 30,000 rpm) offers the ideal prerequisites. In the application, the benchmark is around 7-8 litres of generated chip volume per minute. A challenge for the tools is initially the small size of the pockets, which limits the possible applications of large-format milling cutters.
As a result of the undercut in some pockets and the small corner radii, a large proportion of the machining tasks have to be carried out with rather small-format milling cutters with diameters of only 16 mm for roughing and 12 mm for finishing. MAPAL has developed solid carbide milling cutters especially for such applications – the OptiMill-SPM-Rough for roughing and the OptiMill-SPM-Finish for finishing. Both milling cutters are uncoated. They can remove up to 1,500 chips per second thanks to appropriately designed chip flutes with polished surfaces. The triple-fluted roughing cutter has a conical neck, which makes it particularly resistant to bending. As a supplement the SPM-Rough milling cutter with indexable inserts, also newly developed, is available for areas with suitable geometry and sufficient space.
VIBRATION UNDER CONTROL
A particular challenge in such operations is to avoid vibration“, Michael Hofmann said. The large-format components with their thin walls can easily be excited to cause vibration. This in turn forces a reduced processing speed. This is particularly critical when finishing close to the bottom area of the pockets where a radius must also be maintained in the transition to the base. Vibration can quickly occur here, especially with major wrapping in the corner area at the high
feed rates.
For this reason, MAPAL has developed a new finishing geometry for the milling cutters, especially for finishing deep pockets and filigree component
structures, which prevents a pull effect (i.e. drawing in of the tool into the full material) even with major wrapping. Equally significant is the highly positive geometry of the cutting edges and their asymmetrical pitch. Thanks to the particularly long cutting edges of the four edged finishing cutter, finishing can be carried out in a single pass, even on very deep pockets.
Dear readers,
and business associates,
The coronavirus has maintained its hold over us and we cannot meet face-to-face as we are used to doing. In light of these circumstances, it is all the more important for me to share with you developments at MAPAL and our product portfolio through Impulse. In previous issues of Impulse, I told you that we were also taking and had already taken this time to make changes to our organisation, optimise processes and integrate digital possibilities. We now work much faster and are more broadly positioned for the future. In this issue of Impulse, you will find out more information and insights on this – including in an interview with Jacek Kruszynski, our new CTO.
Of course, we are and remain a family company and retain our DNA. We remain your reliable partner, who – always with your part in mind – use our understanding of processes and our complete range of products and services to make your task the focus of our cooperation. Not only in the quality and precision that you are used to at MAPAL, but also within appropriate delivery times.
We are making use of the new opportunities brought by digitalisation, for example, by quickly and directly organising the transfer of knowhow. In this way, we are ensuring that you will be looked after with the same standards and skills anywhere in the world. Among others, this is taken care of by the newly implemented market segment managers and their teams.
We will also be increasing our utilisation of online channels in future so that we can quickly and directly provide you with information on our services. For this reason, one project we are currently hard at work on is an entirely new online presence that we can use to operate all kinds of digital channels. Watch this space! Our homepage and specific landing pages for news as well as the die & mould sector are already showing first insights into our new online world.
For the time being, many meetings and contacts will remain purely virtual, but I hope that we will be able to see each other in person again soon. Until then, enjoy reading this edition of Impulse.
Best wishes and stay well!
Yours,
Dr Jochen Kress
