Boosting productivity on aerospace component manufacture

Citation

(2002), "Boosting productivity on aerospace component manufacture", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 1. https://doi.org/10.1108/aeat.2002.12774aab.010

Boosting productivity on aerospace component manufacture

Keywords: Grinding, Aerospace, Manufacture

The High Temperature Components Section of aerospace manufacturer Centrax of Newton Abbot, Devon, has ramped-up productivity even further on specific "hotend" precision grinding tasks with the acquisition of two additional Jones & Shipman Dominator 634 CNC Production Surface/ Creepfeed grinders. This brings the company's total complement of Dominators up to four.

The section specialises in the machining of turbine nozzle guide vanes and rotor blades for aero and land-based gas turbine engines. Its first Dominator, a 634 model (600x300mm table) delivered and commissioned in January 2000, is said to have proved invaluable for machining nickel-based, heat-treated HP turbine blades manufactured for the FJ44 turbofan engine.

The FJ44 is a small, lightweight powerplant that brings the economy of the turbofan to the small business aircraft market previously served by turboprop engines.

The compact size and complex profile of the FJ44's HP turbine blades provides a difficult application in terms of workholding and machining – however the purchase of the Dominator, to replace a number of large and unreliable reciprocating-type grinders, has reportedly boosted production.

The blade's fir tree root-end is ground in two operations on the Dominator, with each operation carried out in batches of 1500- 2000. The blade is held in a sophisticated fixture, purpose-designed and developed by Centrax for the task.

Jones & Shipman explains that the fixture supports the aerofoil in six positions, and, through an ingenious design, takes advantage of machining forces to hold the component in place while grinding is carried out.

A productivity boon is said to be an optional Erowa quick-change chuck, which allows the setter to load and unload the fixture quickly, thus removing the "dead" time between set-ups.

Production engineer Patrick Moore says: "We first saw the Dominator at MACH '98 and were very interested in the machine's travelling wheelhead concept and felt that its small footprint would suit our production needs perfectly. Some time later, when visiting a customer – a world-leading aerospace engine manufacturer we saw a Dominator grinding powerplant components and were most impressed."

"We reviewed our then current grinding machine inventory and looked at other suitable new products on the market and deduced that the Dominator offered a significantly-reduced footprint, excellent cycle times, strong health and safety features such as totally enclosed guarding, leak-free operation, robust design and on-line modem support. Naturally then, when funding became available, the Dominator was the obvious choice."

The Dominator concept claims a total rethink of the surface grinding process. Incorporating a reciprocating wheelhead rather than a traditional reciprocating table design, major advances have reportedly been achieved in respect of structural rigidity, machine dynamics and smaller machine envelope.

Patrick was also impressed with the easy-to- use programming system. Windows-based set-up pages allow the operator to quickly digitise diamond roll and wheel positions, and, by minimum use of mouse or keyboard inputs, produce a finished program. Graphical images prompt the operator, and spreadsheet-style programming ensures quick and simple input. The option of ISO programming is also available if required.

Commenting, Patrick said: "The Windows- based programming system allows us to input various parameters at any time during the cycle, therefore it can be as flexible as you like – unlike many other systems. Also, it is so easy-to-use that an operator/setter can be fully conversant with the Dominator in a week or even less."

With the success of the first Dominator, a second machine, an original 634 model, was brought in by Centrax on lease to cope with a temporary production peak. As with the first Dominator, the on-lease machine impressed with its production capacity, ultra-reliability and small footprint, so much so that the company decided to buy it (Plate 5).

This second Dominator is used for a variety of applications including two-axis radial tip grinding of LP compressor rotor blades. The application is both demanding and time- consuming, requiring the machining of a fine tolerance arc in both (X) and (Y) axes.

Plate 5 Securing a blade for grinding on a Dominator 634 CNC production surface/creepfeed grinder

"When we used large creepfeed grinders on this application, the surface finish was not always of the required standard, with "facet" marks often left along the length of the radial tip. However, since applying the Dominator to this work, productivity and surface finish have been excellent, and we are using it more-and-more for this type of application," adds Patrick.

Now with the installation and commissioning of a further two Dominator model 634's, Centrax is achieving a further boost in production – this time on the GMA 2100 engine line, where both machines are grinding Inconel compressor blade root features.

Another feature of the Dominator purchase is said to be the close technical co-operation that has occurred between Centrax and Jones & Shipman International, ensuring the relationship between the companies has developed into more than that of mere client/ supplier.

On the original Dominator 634, Centrax had a requirement to raise the diamond roll dresser centre line by variable amounts and wanted interchangeable diamond roll spindles manufactured that could be stored and re-assembled quickly and easily.

Patrick says: "With close collaboration between the two companies, Jones & Shipman designed, developed and manufactured a diamond roll dresser based on a sine bar principal. The unit also gives us a fully interchangeable diamond roll spindle facility, allowing us to store bespoke diamond roll arrangements that aid setting and storage. The dresser also incorporates a variable height facility. In all, Jones & Shipman has been very helpful on this project."

Summing up, Patrick says: "For high production, reciprocating and creepfeed grinding applications I wouldn't hesitate in specifying another Dominator. Product, service backup and application support from Jones & Shipman International has been absolutely first-class."

Details available from: Jones & Shipman International, Tel: +44 (0) 116 289 6222; Fax: +44 (0) 116 289 2945; E-mail: mduignan@rpt.uk.renold.com ; Website: www.renold.com/machines