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Laser & Waterjet Profiling
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Manufacturer and supplier of carbide cutting tools and tooling systems Seco Tools, has, since 2004, been working in partnership with the UK division of global landing gear specialist Messier-Bugatti-Dowty (MBD) developing efficient and cost-effective methods to machine high quality, complex titanium components used in today’s modern, advanced aircraft.
Although manufacturing large structural components for aircraft landing gear is a primary business activity at MBD Gloucester, the challenge presented by the truck beam on Boeing’s 787 Dreamliner has tested every ounce of the company’s resolve and engineering prowess.
This was largely due to the new, specially-developed 5-5-5-3 next generation titanium alloy used in the truck beam and in particular to the fact that no suitable cutting tools and little cutting tool data regarding the machining of the material existed back in 2003 when the project started.
“The use of the new material was an obvious choice,” explains MBD’s manufacturing engineering systems manager, Malcolm Page. “It offers an impressive strength to weight ratio and with just a 1% weight saving on an aircraft’s empty weight being able to deliver 3% less fuel burn, the rewards are significant – particularly seeing as fuel now represents more than 30% of total costs for airlines.”
To help develop a machining solution, MBD invited a number of preferred cutting tool suppliers to the table with the objective of accelerating the development process. Seco Tools, being one of the companies invited and armed with significant expertise and knowledge of machining standard titanium, performed its first cutting trials in 2004. While efficiency and cost were important considerations, the critical factor throughout was quality.
“With over 130 tonnes of down force expected on each truck beam there is clearly no place for poorly machined components or parts of variable quality,” Mr Page explains. “Furthermore because each billet of 5-5-5-3 is very expensive, producing scrap is simply not an option, especially as the project represented MBD’s first commercial landing gear contract for Boeing.”
The machine tool selected to perform the roughing operations on the forged titanium billets was a six spindle DST Droop & Rein CNC milling machine. During the early stages of the trials, cutting tool life, due to the creation of extreme heat and the cutting forces involved, was understandably low. But the Seco Tools’ team, which included David Pearson and Dave Todd based in the UK, as well as a number of engineers located at Seco's headquarters in Sweden, set about modifying the micro geometry of the cutting edge to improve performance. This, in conjunction with ongoing grade trials and constant adjustment to cutting strategies and parameters, led to the evolution of a stable and repeatable process.
The Seco solution is based on the use of an 80mm diameter helical cutter (R220.69 Power Turbo) plus copy mills (R220.29) fitted with five modified 20mm button inserts (RPHT.2006) that use a special variant of carbide grade – T350M. The cutter is used to profile plunge mill the forged billet – an operation that roughs away approximately 30mm of stock from the component surface.
“We had a ‘must-cost’ target for this operation that we simply had to achieve,” Mr Page adds. “If we say the target represents a ratio of ‘1’ – which is where we are now – after the initial cutting trials we were at a ratio of 1.6, which shows how far we have come on this project. Essentially we have cut roughing time by 60-70% through our partnership with tooling suppliers.”
Mr Page is keen to praise the efforts of the Seco team in helping to provide a solution to the manufacturing challenges. “We all had to go back to basics,” he says. “The material was new so no data existed, which meant that a fair amount of guesswork was involved and we had to go back to first principles. Through trialling and testing we refined our initial ideas and increased our collective understanding. It was an iterative process.
“The eventual solution has not been derived through the simple application of existing technology, but as a result of knowledgeable engineers who have demonstrated the ability to solve a tough manufacturing problem. The input from Seco Tools both here and at our sister company in Bidos, France has been first class and demonstrates how Seco is able to provide the optimum solution to what was a very complex manufacturing problem.”
The partnership continues between MBD and Seco Tools. Both are currently are working together on coating technologies to improve the machining process further.