08/01/2007
Inserts and milling cutters – tailored to your needs
CERATIZIT helps Gardner Aerospace with tooling problems |
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CERATIZIT S.A., Mamer, Luxembourg (headquarters and parent company) and Reutte, Austria (parent company), December 2006. High speed cutting for cutting tools is not only about the selection of suitable inserts, but also about the right combination of tools and their optimum application. For key accounts the carbide manufacturer CERATIZIT develops tailor-made solutions according to customer request – as was the case for Gardner Aerospace. The Hull based company in Great Britain is part of the Gardner Limited group and specialises in long and large components such as aircraft wing skins.
“Many people think that aeroplane wings are simply covered with a plain sheet of aluminium,“ says Nathan Paxton, CERATIZIT’s Key Account Technical Manager in the UK. “In fact most modern commercial jet wing panels are highly complex components, which are fully integrated into the structure of the aircraft. They are machined from a single solid block, with variations in thickness, integral supporting ribs and access panels“.
The challenge
As Paul Smith, Gardner Aerospace’s Engineering/Manufacturing Manager was aware of this know-how he directly referred to CERATIZIT UK. “If the cutter design is not 100% suitable, the machining of these wing skins is critical, and we can experience what we know as ‘cutter abuse’. This is where the cutter is generating too much heat and causes damage to the material being cut or to the component.” Before CERATIZIT was involved, Gardner Aerospace used a standardised manufacturing method for aeroplane wings. The component was machined complete with free-form curved outer and inner surfaces with special tools. In order to guarantee the high surface quality priority number one was to eliminate 'stress concentrators’ such as sharp corners. This led to a standardisation on inserts with radii of 19.05 mm (3/4 inch). After this, however, the existing cutters suffered from design features that severely limited their maximum speed. The low cutting angle inherent in these tools created inefficiencies in terms of power to metal removal.
The tailor-made solution is called AFC (Air Foil Cutter)
Nathan Paxton accepted the challenge and quickly found a perfectly suited solution together with the experts from the CERATIZIT Cutting Tool division, namely the Air Foil Cutter for high rake inserts. The unique radial location feature and the use of two high-strength location screws per insert allows a typical 75 mm diameter cutter to be operated at spindle speeds over 21.000 revs/min. In addition Gardner Aerospace now applies large, full-quarter segment inserts that allow depths of cut up to 20 mm, which is typically the length of the bosses and ribs found on wing skins. Alternatively a smaller insert plus a spacer for shallower cuts can be used. The major advantage of the tailor-made tool design: multiple effective cutting edges per cutter combined with higher rotational speeds make higher feed rates possible. The softer cutting action provided by the high positive rake also eliminates the risk of ‘cutter abuse’, the scenario most feared by the operators. And what is more: The forces on the machine spindle are reduced, machining performance is improved and any additional cost is offset.
On site support
As a particular service CERATIZIT sent a team of specialised engineers to support Gardner Aerospace. They compared the cutting data for the new milling cutters and trained the machine programmers and operators. Gardner Aerospace can now the safely manage to achieve the optimum chip volume and the requested quality, even when the wall thickness of the component is only 0.8 mm in places. “Having worked with CERATIZIT for a number of years in other projects we were familiar with their quality and high levels of customer service,” says Paul Smith. “However, CERATIZIT excelled itself on this particular application as the lead times that we are given by our customers are relatively short and in all cases CERATIZIT has been able to design and manufacture cutters for a range of components within the required time frame for us to maintain production. It is reassuring to be able to tell a tooling supplier what it is you require secure in the knowledge that within 4 – 6 weeks we will receive cutters and inserts ready for use.”
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Specials
