Right first time
Keywords: Aerospace, BAE Systems, Bridgeport, Machining
Bridgeport engineers were delighted to receive an Invitation from defence and aerospace giant BAE Systems to compete for the supply of additional Vertical Machining Centres to its Brough site. As part of the short-listed selection process, Bridgeport were asked to machine a couple of aluminium components at the Bridgeport Technical Centre in Leicester UK. It was intended that the first could be used to "gain experience" and then BAE staff could visit to see the second machined into a finished part. When the BAE Systems team arrived for the application machining demonstration, they were impressed to find that both components were right in every respect and could be put into the supply chain immediately (Plates 2, 3 and 4).
Plate 2 The three newly-installed Bridgeport VMC 2000 digital machines at BAE Systems, Brough. (Photo courtesy of Andrew Delgaty, BAE Systems)
Plate 3 This selection of components, at BAE Systems, all machined from solid light alloy billits, graphically illustrate how much metal is removed by the Bridgeport machining centres. (Photo courtesy of Andrew Delgaty, BAE Systems)
Plate 4 A "work in progress" shot of a light alloy frame showing the complex geometry involved in machining operations using the Bridgeport vertical machining centres at BAE Systems. (Photo courtesy of Andrew Delgaty, BAE Systems)
The Brough site, is at the very heart of the BAE Systems aircraft programmes and has recently seen Hawk production transformed through the introduction of lean manufacturing techniques. It has also benefited from a programme of investment, the latest element of which has been the introduction of three Bridgeport VMC 2000 portal-type vertical machining centres. The machines were purchased to satisfy an influx of machining detail requirements for a number of aircraft projects.
Keeping the work in-house
The increase in workload could have been met by sub-contracting out, but BAE Systems knew that, if a sufficiently strong case could be made after finding suitable machine tools with a short enough pay-back period, the work could be kept in-house. Time was of the essence as the team went into action. In March,this year, a shortlist of potentially suitable suppliers was ready and resulted in the trials highlighted above being carried out a few weeks later. Two standard Bridgeport vertical machining centres were ordered as a result, the first installed in April and, because no foundation work was required,immediately put to work with the second machine following soon after.
Improved productivity
Similar components to those being machined were – and still are –manufactured at Brough on a larger Japanese machining centre but production on the new machines reportedly shows a 15 per cent reduction in machining time. According to Bridgeport the combination of lower initial cost and improved performance, along with intensive use, meant that the Return On Investment (ROI)period could be measured in a matter of months, resulting in the ability to purchase a third Bridgeport machine, which was installed in September.
High metal removal with good swarf clearance
Brough has always been in the forefront of high metal removal processes, or integrally machined components. This expertise goes right back to its development of the famous Buccaneer aircraft and the site continues to use this approach today. It has refined the employment of high-speed machining to a fine degree combining the Bridgeport VMC 2000's 15,000 rpm spindle option with a 7m/min feed rate to typically plough off up to 80 per cent of the original billet weight. With such high metal removal rates, good swarf clearance is vital; not only is the swarf removal system up to the task, but also it came as a standard item.
Transferable CNC programming
With the original large-format machining centre running under GE Fanuc control, it might have been expected that BAE Systems would have specified the same CNC supplier for the new machines by taking advantage of Bridgeport's policy of offering a choice of controls. In this instance, however, the overriding need was a rapid installation and so, because the first available machine had Heidenhain 426P controls already installed, these were used on all three. BAE Systems has access to a first-class team of software engineers who came up with an excellent conversion programme that easily transforms any existing machining programme from one system to the other. This is so effective that new parts are programmed for the familiar GE Fanuc control in the usual way and, if to be machined on a Bridgeport, the programme is simply transposed accordingly.
Machining flexibility
The method developed for sculptor- machining of billets at Brough is believed to be extremely flexible, thanks to a system that uses standard sub-tables fitted to the machine beds. These have common locations for fixing any size of billet to them, thereby making for simple and fast set-up. A 'picture-frame'method is then used to machine out the component from the billet, either at a single setting or with one change involving a rapid inversion of the part. The component can then be 'broken out' from its frame in a rather similar way to the breaking-out of plastic parts from their sprues.
With all the requirements regarding tolerances and surface finish being achieved, all relevant parts falling within an 800 x 2,000mm billet size are now scheduled for manufacture on the new machines. No tooling changes were needed as the optional BT 40 spindle to match existing machines was specified.
The BAE Systems team is reported to be very pleased with the performance of the machines and with the support received from the technical staff at Bridgeport.
Acknowledgements
Bridgeport Machines would like to thank Graham McNish and Sarah Hesslewood,BAE Systems, for their help in the compilation of this feature.
Details available from: Bridgeport Machines Ltd. Tel: +44 (0) 116 253 1122;Fax: +44 (0) 116 253 9960.
