Stealth and supersonic. These are two attributes of the most dominant and complex military combat fighter jet in the world - the F-35 Lightning II produced by Lockheed Martin. These words also describe the precise capabilities of Starrag’s manufacturing machines, with more than 60 Starrag installations involved in the creation of each F-35.

It takes a single pilot to manoeuvre the $100 million jet, but it takes thousands of Joint Strike Fighter (JSF) partners to construct the F-35 to ensure the pilot has the most superior fighter apparatus in the world. Starrag is one of those partners, with its machines producing a wide range of specialised components from steel, aluminium and titanium.

“It’s a heart-stopping moment when you attend an airshow or are at a stadium when the US military conducts a flyover with the F-35,” says Starrag chief sales officer, Alexander Attenberger. “We swell with pride knowing that Starrag plays a role in the JSF programme, which is planned to continue for possibly another 50 years.”

The first F-35 flight launched in 2006 and Starrag’s involvement with the programme began in the early 2000s when it worked with a UK-based customer on titanium parts. Starrag previously had developed tailored machines for machining parts for other aircraft for this customer and other manufacturers.

“Starrag’s extensive experience of machining titanium was extremely competitive, particularly in regard to tool costs, which are the largest ongoing lifecycle costs of machining,” begins Starrag managing director, Dr Bernhard Bringmann.

Really big machining

The joint work and developments soon evolved into Starrag’s BTP (Big Titanium Profiler) machining centre with pallet sizes of 5,000 x 2,000mm to accommodate the machining of stringers. Today, 23 BTPs are in production factories in the UK and Australia.

With 1,000Nm twin spindles and a tool magazine with more than 400 pockets, the BTP 5000/2 simultaneously mills titanium tail fin components of 700–800mm width and just 50mm thick to tolerances within 30µm and to surface finish qualities of Ra 1.6 (for 5-axis tasks) and Ra 0.8 (3-axis). To ensure those demands are consistently met, Starrag’s quality turnkey solutions include the construction of a machine foundation 2,000mm deep to ensure sufficient stability.

Even the earliest machines installed are continuing to hold the specified volumetric tolerances – in some cases, maintaining 50µm across the machining envelope with ranges that extend to 4,800 x 3,000 x 1,500mm.

"With our ongoing support, there is no reason why our JSF customers shouldn’t continue to maintain such high accuracies day in and day out for the next five decades,” states Bringmann. “For every machine and flexible manufacturing system (FMS) we provide, we work very closely with the customer to provide the perfect machining solution to achieve the best quality and cost-effective end result.”

The capabilities of the Starrag Group’s Droop+Rein FOGS overhead gantry-type 6-axis machining centres are also utilised for F-35 work, not only for high-speed finishing of dies, but especially for the fixed, fork-type heads with 300Nm spindle. Starrag continuously developed its revolutionary FOGS models to efficiently rough machine a range of steel and titanium F-35 components using a variety of heads. The 6-axis Droop+Rein is the only one of its kind in the world.

Coping with carbon

Carbon fibre is another material in Starrag’s machining portfolio, in one case involving an FMS based around FOGS machines housed in a large, temperature-controlled building. The FMS accommodates certain panel configurations that need surface milling, routing and drilling in a single set-up before being cleaned and passed to an integrated co-ordinate measuring machine. The workpieces sit in fixtures on pallets that are moved under constant vacuum to the inspection machine.

In addition, the FMS features enhanced control software. Starrag’s kinematic management system enables the FOGS machines to hold tolerances of 50µm over their entire 4,800 x 3,000 x 1,500mm working envelope while cutting in fully interpolative 5-axis mode. Initially established with five machines, the FMS now has nine machines served by a 90-pallet Fastems system.

Starrag’s workable concept of the interchangeability of machined parts was also borne from the JSF programme. With parts being manufactured from around the world, the programme required that all of them meet very stringent tolerance specifications for interchangeability within the aircraft. Starrag, which had similar accuracy specifications to meet the production of the Eurofighter Typhoon jet, was successfully able to meet those stringent interchangeability standards. Initially supplying a tailored horizontal machining centre, Starrag added volumetric compensation routines to a standard FOGS model to complete these complex tasks.

The combination of Starrag’s expertise and the input of the customer’s accumulation of knowledge from its business standpoint is what creates optimised production solutions. In addition to machine build quality, this ongoing quest also involves CNC software, fixtures and workholding, as well as tool design and development.

“Our solutions not only have to provide immediate results in terms of lowest cost per part at the expected quality level, but they also have to sustain over the lifecycle of the part,” concludes Bringmann. “In JSF’s case, this could mean another 50 years.”

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