Ready for composites?

With around 50 per cent (by weight) of a Boeing 787 Dreamliner manufactured from composite materials, and with well over 800 aircraft on order, the demands on manufacturers to fully understand the use and machining of these materials is growing by the day. This is just one aircraft from one manufacturer. Factor in the other aircraft companies who, in their drive for fuel economy, will use more and more composite materials and there will be massive growth in the composite machining market. Add to this the other industries that are turning their eyes to composites, where anyone manufacturing products requiring strength and low weight will, at some point, manufacture from composite materials, and you can see the potential. Automotive, for example, will, once the inherent problem of mass production of composites has been overcome, employ the technology currently in use in motorsport for suspension, chassis and bodywork components. While development work is undertaken by OEMs and tier one suppliers, mainstream production will be the domain of the thousands of subcontractors across the world. Many have moved away from high-volume, low-cost part production and have invaluable experience machining 'exotic' materials for high added value components. Therefore, the move to machining composites should not be that big a step for them. And support is there from a range of companies, like WNT (UK). It will be needed, as composites have their own particular issues when it comes to machining them. The majority of composite applications (aerospace and motorsport) require free-form, aerodynamic, shapes and, by the time they come to be machined, are of high value, so mistakes are expensive and unacceptable. Before the first cut is made, subcontractors need a full grasp of the technology needed to successfully cut a part. Workholding, for instance, is a major issue, and vacuum systems with base plates that mirror the actual component are a common feature. Vacuum workholding also leads to a requirement for tools that push the workpiece into the 'fixture' – a right-hand tool with a left-hand helix - unlike machining where right-hand helix tools are used. Also, when machining honeycomb-style composites, you need a tool that combines a left and right-hand helix to avoid damage to the upper and lower layers of the composite sandwich. Another challenge is the abrasive quality of composites such as carbon fibre. While machining relatively easily, it is extremely abrasive. This is where poly-crystalline diamond tools (PCD) can play a part. But, while in traditional machining applications PCD tools have been used in lighter finishing applications and carbide used for roughing, in the case of composites, this may be reversed. So, there is more to machining composites than meets the eye and now is the time to be researching best practice, in order to take full advantage of the tremendous opportunities that are just around the corner for UK-based subcontractors. First published in Machinery, October 2010