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COMPOSITES I TOOLING 32 AEROSPACEMANUFACTURING | SEPTEMBER 2010


COLLABORATION PROVIDES


THE EDGE C


onventional metalcutting tooling is still widely used in machining of composites and


could be detrimental to productivity and product quality. Pioneering research and development through the partnership of Airbus UK and precision tool specialist SGS Carbide Tool is said to deliver substantial benefits in understanding the most effective machining strategy for aerospace grade carbon fibre reinforced plastic (CFRP) composites for primary aerostructures. The breakthrough has elevated both parties to the forefront of knowledge in composite machining. A recent case study was carried out by


SGS with the Manufacturing Engineering Research department of the Airbus Wing Centre of Excellence (CoE) at Filton. The objective was to evaluate and optimise the machining strategy before production of composite components. SGS first introduced a purpose- designed CFRP composite cutting tool to Airbus in early 2008. Early test results did not provide any benefits, compared to baseline PCD tooling. After introducing a number of modifications to the existing design and optimisation of machining conditions, significant improvements in productivity, surface quality and tool life were achieved. Further benchmark testing has shown that the redesigned router outperformed PCD tooling in a number of instances when machining CFRP composites. The Airbus trials have also enabled SGS to develop its carbon composite


Cut to the chase: SGS helped Airbus’ Wing Centre of Excellence evaluate and optimise the machining strategy before production of composite components


router through real-life test analysis, as field sales manager, Wesley Tonks, explains: “The Airbus collaboration has accelerated the tool’s development significantly and we have been developing special derivatives of the tools to test which is to all our customers’ benefit in time. The results have been extremely beneficial both to us and to Airbus in generating a greater understanding of the most effective methods of machining CFRP composites. “As further testing progressed, in harmony with further tool development, we have been able to cut deeper with our specially developed long shank


Despite the growing use of composites in high-end manufacturing sectors, the research into effective machining of composite materials is still in its infancy.


tools whilst maintaining consistently high quality results. However, the issue that became more critical to effective carbon composite machining in these circumstances is the effective removal of waste material to reduce the tendency of the ultra-fine swarf to clog.” This has triggered additional research


with Airbus’ machine tool supplier, MTorres to investigate and create an effective low pressure zone/vacuum around the tool to remove dust most efficiently. The research has taken some 24 months to improve understanding of the fundamentals of composite machining with a focus on the milling of CFRP composite materials. The review looked at work undertaken by the major players in the aerospace industry at a time when polycrystalline diamond (PCD) tooling was commonly used by the industry. A number of leading PCD tooling suppliers were contacted and their cutting tools were tested on baseline CFRP materials to be used on the A350 XWB. Slotting was chosen as this was the


most demanding operation due to the deployment of up and down milling in one revolution cut and the tendency of clogging in the slot. The test criteria included uncut fibres on the top/bottom ply, onset of vibration and residual dust in the slot. SGS concluded that the choice of cutting speed is critical as it will affect


the wear mechanism. ❙ www.sgstool.com


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