Aerospace supplier invests in new technology

Citation

(2001), "Aerospace supplier invests in new technology", Aircraft Engineering and Aerospace Technology, Vol. 73 No. 4. https://doi.org/10.1108/aeat.2001.12773dab.002

Aerospace supplier invests in new technology

Aerospace supplier invests in new technologyKeywords: Bridgeport Machines, Centrax, Grinding,

As a major supplier of machined components to aero-engine companies for more than 50 years, Centrax Ltd which are based at Newton Abbot, UK, has always taken full advantage of the latest developments in machine tool technology. Now in the process of updating its manufacturing facilities, the company is embracing an entirely new concept for production grinding, following the installation of Bridgeport's new FGC 1000 flexible grinding centres (Plates 1-3).

The growth in world demand for regional jet aircraft engines has helped boost Centrax to such an extent that there has been an urgent need to expand manufacturing capacity. The growth programme, set to take the privately-owned company's turnover to more than £70 million, is widely based. Turbine component and assembly business comes not only from engine makers in the UK, but also from the rest of Europe, the USA and even Japan.

Plate 1 An example of aero-engine turbine blades before and after grinding on the new Bridgeport flexible grinding centres at Centrax Ltd

Plate 2 Two of the new Bridgeport FGC 1000 flexible grinding centres, in production at Centrax Ltd, showing a selection of special grinding wheels used

Plate 3 A typical set-up on a Bridgeport flexible grinding centre, showing grinding turbine blades at Centrax Ltd

The increase in the level of business demanded a significant investment programme to increase capacity. Centrax took the opportunity to move from analogue controlled machining centres to the latest digital controlled machines. A thorough review of the market resulted in a short list of machine builders being selected for trials from which Bridgeport emerged as the supplier of choice.

The initial investment programme is well underway and when completed will see around 20 Bridgeport machining centres installed at Centrax. They will all be high level specification machines including 12,000rpm spindles, 30 station automatic tool changers, linear scales and Heidenhain digital control systems. This technology, says Tony Wiltshire, "is the key to greater quality, allied to much higher productivity". He is too modest to add that the ability of his own production engineers to adapt the latest manufacturing technology to their own specialised needs, by way of some very clever tooling, is probably just as important. This application of in-house customisation is particularly rewarding when taking advantage of the machines' five-axis capability and high speed machining functions of the control system.

Important to Centrax was the timing of Bridgeport's recent introduction of the new FGC 1000 flexible grinding centres. These machines utilise the Rolls Royce patented "Viper" process. Tony Wiltshire and his team were quick to recognise the amazing potential this step-change in grinding technology provided for turbine blade production.

The final decision came at the MACH 2000 Exhibition in Birmingham, when Bridgeport Machines received an order from Centrax for their first flexible grinding centre with Viper technology. Four of these machines are already in production at the Centrax, Newton Abbot facility.

Until now, blade roots had been precision ground on a series of quite massive (and expensive) creep-feed grinding machines, with the components having to be transferred, one stage at a time, through a succession of anything up to seven machines. According to Bridgeport traditional creep feed grinding, itself a revolutionary production process in its time, is now seen to be slow and labour intensive. The company also considers that in addition, the cost of tooling for a whole line of machines for each component, plus the consumption of special expensive, large diameter "soft" abrasive grinding wheels was found to be a major drawback.

The new process, utilising the Bridgeport FGC machines, allows multiple machining operations to be completed in only one set up. This has provided significant savings in the time taken to fully grind a typical blade on all features in one or two machine loads. Each machine is equipped with a Nikken rotary table, controlled by two of the five axes available via the control system. Tony Wiltshire says, "These machines will each do the work of four or five creep-feed machines".

Wheel dressing is fully automatic and is generally carried out within cycle. The tool carousel can accommodate up to ten wheels with a maximum diameter of 220mm.

Said Tony Wiltshire: "Bridgeport did everything we asked of them and close factory support was evident from the start. It was also very impressive the way our test piece was manufactured without any fuss and, being a domestic manufacturer, we were pleased to be talking direct to the people involved".

As for the flexible grinding centre concept, Centrax engineers who visited Bridgeport at the time of an open-house to launch the machine came away feeling that the machine builder exuded confidence and "knew what they were doing".

Now the Centrax team members say they are delighted to be "in at the birth" of such an innovative new process and are confident that the company's place as a prominent turbine blade manufacturer is ensured for the foreseeable future.

Further details are available from Bridgeport Machines Ltd. Tel: +44 (0) 116 253 1122; Fax: +44 (0) 116 253 9960.