Complex machining of Eurofighter Typhoon wing parts

Citation

(1999), "Complex machining of Eurofighter Typhoon wing parts", Aircraft Engineering and Aerospace Technology, Vol. 71 No. 6. https://doi.org/10.1108/aeat.1999.12771faf.004

Complex machining of Eurofighter Typhoon wing parts

Keywords Tooling, Milling, Components, Fixtures, Wings, Aircraft

An Okuma MacTurn 50 mill-turn centre is being configured by UK agent, NCMT, to complete the majority of the operations required to produce the left and right hand foreplane spigots which adjust the canard wing positions on the Eurofighter Typhoon. The cell is due to be installed at the British Aerospace Samlesbury site, near Blackburn, by mid 2000.

Along with the MacTurn 50, additional equipment to be supplied under the turnkey contract includes a Forkardt quick-change spindle nose and setting station for component/fixture assembly, a Messma Kelch tool presetter connected directly to the lathe control, a manual handling system from Dalmec for loading both the machine and the setting facility, and program generation equipment to enable scan milling of complex surfaces.

Included also are a workholding package to interface with the quick change system on the lathe, BIG Daishowa Seiki BT50 spindle tooling for rotating tools (also from NCMT) and Sandvik holders for both rotating and turning tools. The turning tools have been specified with Capto interface to reduce cutting tool setting times. Detailed applications engineering and full project management are also being supplied by NCMT.

The machining sequence for both left and right hand spigots comprises 11 operations, of which ops 20, 30, 60, 80 and 90 involving turning, milling, drilling, boring and threading are performed on the MacTurn 50. Of particular interest is believed to be the way in which, as the part progresses through its manufacturing cycle, datum faces and bores are machined to locate and clamp the component during subsequent operations.

The forgings are supplied to the cell with the barrel turned to a defined tolerance and are presented on stillages in the correct orientation for loading into the fixture. The op 20 collet-type fixture is clamped onto the headstock of a separate off-machine setting facility. The component is clamped into the fixture so that the blade slot centreline runs parallel to that of the machine tool.

The component/fixture assembly is loaded to the machine spindle nose with the help of lifting equipment. The fixture is radially located then hydraulically clamped to the spindle nose by means of a foot switch, an air sensing system then ensuring correct fixture location. The cycle consists of machining the initial component datums and rough milling the blade faces. Each loading for subsequent operations is similarly executed.

Op 30 involves locating the component with the blade end of the component toward the machine headstock in a slave fixture using datums machined during op 20 and then clamping the part via tapped holes also machined during the previous operation. The machining cycle consists of rough and fine turning, advancing a hydraulic steady rest for component location, retracting the tailstock to allow access to the internal features of the component, U-drilling a 54 mm diameter hole to a depth of 216 mm, various rough boring operations on the chamber, and profile milling of the surfaces.

Op 60 is preceded by rough slot machining on dedicated equipment and heat treatment in a fixture to prevent undue distortion. In the MacTurn 50, the part is clamped as for op 20. The cycle starts by advancing the hydraulic tailstock fitted with a special damping device to eliminate blade vibration due to the fact that the slot has now been machined. Metalcutting is restricted to proof machining of the tooling lug faces, opening up existing dowel holes and reaming location holes.

Op 70 is finish machining of the slot, again on dedicated machinery. During op 80, new location holes are drilled and reamed, component clamping holes are drilled and counterbored, and drilling and fine boring is performed between the blades into the barrel section.

The last stage on the MacTurn 50 is op 90, for which the component is fixtured with the blade end of the component towards the machine headstock. A complex sequence of finish machining operations is performed including turning, drilling, threading, boring, and scan milling. An angle head is used for part of the cycle to drill and fine bore one of the holes. Subsequent ops 100 and 110 are for finish grinding the journals and for frazing respectively.

The MacTurn 50 itself is a little different from the standard version. It has a 72-tool magazine instead of the normal 32 tools, a 37/30 kW spindle motor and larger spindle bearings to support the heavy fixturing.

An automatic work gauging and offset system is based on Renishaw probing. Tool life management software is included to enable the use of sister tooling. BIG plus spindles have also been specified on both stationary and rotating spindles to give additional rigidity during machining.

Other facilities are air blow for the tailstock centre, Abso scales for the X, Y and Z axes for improved accuracy and repeatability, and high pressure coolant for deep hole drilling and boring. Swarf and coolant management includes a 50 micron medialess filtration system. Owing to the size of the machining programs, a DNC interface is provided to drip feed the programs to the Okuma CNC system.

Geometric accuracy tests on the machine will be carried out by Okuma in Japan. When the machine arrives in Britain, it will be installed at NCMT's technical centre where initial part programs will be prepared, followed by set-up and prove-out for both left and right hand foreplane spigot components for each of the five ops on the MacTurn 50. Once installed at Samlesbury, the tests will be repeated to include a machine run off of 30 components to SPC criteria.

Details available from NCMT Ltd. Tel: + 44 (0) 181 398 4277; Fax: + 44 (0) 181 398 363 1.