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Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Aircraft construction: aluminium, titanium or steel?
Article Type: Aerospace technology From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 2.
The Dörries Scharmann Technologie GmbH (DST) stand at the recent Airtec exhibition in Frankfurt focused on high-productivity cutting methods for different metals. The Mönchengladbach Company certainly has some excellent results to show off impressive figures for cutting high-strength aircraft aluminium and cutting performance that is far many times better than conventional solutions when it comes to complete machining of titanium.
DST has reportedly raised the world cutting record for milling structural components for the Airbus to 10 l/min, e.g. for the Airbus. Even more impressive is the fact that the parallel kinematic Sprint Z3 processing machining head achieves this figure in continuous operation, not just for a short time (Figure 1). This allows the operator to convert these record figures into maximum long-term productivity. The new spindle achieves a power of 120kW (100 per cent DC), speeds of 13,800- 30,000rpm and a maximum of 83Nm. Visitors to Stand in Frankfurt were able to see the results for themselves demonstrated using actual work pieces. For the Sprint Z3, the designers in Mönchengladbach have also developed an additional angle d head. It can be interchanged automatically like any other tool and allows the machining angle to be extended from the original 908 cone to more than 1808.
Figure 1 The dynamic parallel kinematic Sprint Z3 machining head cuts up to 10 l/min of high-strength aircraft aluminium
The new ECOFORCE machining centre combines the synergy of proven modules in a concept that is designed specially for titanium (Figure 2), which is a particularly difficult metal to cut. Compared to conventional machining centres, the focus is on increased stiffness rigidity, damping and feed forces. This is the only way to obtain high productivity while simultaneously achieving excellent accuracy, reliability and availability. Because of the high-cutting power required and the resulting high and safe material removal cut metal discharge mechanism, the spindle is positioned horizontally. Hydrostatic guides for the linear axes guarantee the required damping and provide continuous high- cutting performance over. Automatically interchangeable machining heads from a pick-up magazine achieve up to 450cm3/ min for three axis roughing machining and 140cm3/min for five-axis finishing. Roughing Power of 60kW is available at a maximum of 4,000Nm (2,000rpm) and finishing power 40kW at a maximum of 1,100Nm (5,000rpm). For rough machining, interchangeable fixed working milling heads carry out the cutting, while for finishing the tool is guided by a fork type head. The WERO tool magazine provides the user with a selection of up to 4,210 tools. Depending on the design of the ECOFORCE machining centre, work pieces can be up to 3,500 x 6,300mm and a maximum weight of 12,000kg.
Figure 2 High productivity titanium machining is a challenge that DST has met with a new machining centre for rough machining and finishing, specially designed for titanium
On modern aircraft, high-strength steels are used as a material for parts including complex landing gears struts. DST produces different cutting solutions for these and other components. Developed in conjunction with the aviation Aircraft Industry itself, the aircraft manufacturer's investment is well worthwhile, both in terms of from a quality and a productivity perspective.