Stealth and supersonic are two attributes associated with the F-35 Lightning produced by Lockheed Martin, an aircraft that has been described as “the most dominant and complex military combat fighter jet in the world”; and while it takes a single pilot to manoeuvre the $100 million jet, it takes thousands of Joint Strike Fighter (JSF) partners to construct the F-35 — along with more than 60 Starrag machining installations that are producing a wide range of JSF components from steel, aluminum and titanium.

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

While the first F-35 flight took place in 2006, Starrag’s involvement with the programme had begun in the early 2000s when it worked with a UK-based customer on machining titanium parts. Bernhard Bringmann, Starrag’s managing director, says the company had previously developed ‘tailored machines’ for this customer — and other manufacturers — that were used for machining aircraft parts.

“Starrag’s extensive experience of machining titanium ensured a high level of competitiveness, particularly with regard to tool costs, which are the largest ongoing life cycle costs of machining.”

Further development work resulted in Starrag introducing its BTP (big titanium profiler) machining centre, which has pallet sizes of 5,000 x 2,000mm to accommodate the machining of stringers. Today, 23 BTPs are in production at factories in the UK and Australia.

Featuring twin spindles offering 1,000Nm of torque and a tool magazine with more than 400 pockets, the BTP 5000/2 can simultaneously mill titanium tail fin components that are 700-800mm wide and just 50mm thick to tolerances within 30µm and surface finishes of Ra 1.6 (for five-axis tasks) and Ra 0.8 (three-axis). To ensure these requirements are consistently met, Starrag’s turn-key solutions include the construction of a 2,000mm-deep machine foundation, to ensure stability.

Maintaining tolerance
Mr Bringmann says that even the earliest machines installed are continuing to hold the specified volumetric tolerances — in some cases maintaining 50µm throughout machining envelopes 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. For every machine and flexible manufacturing system 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.”

Meanwhile, the capabilities of the Droop+ Rein FOGS overhead-gantry-type six-axis machining centres are also used for JSF work, using a variety of machining heads to rough machine a range of steel and titanium F-35 components.

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.

This FMS accommodates panels 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. It also features Starrag’s kinematic management system that enables the FOGS machines to hold tolerances of 50µm over their entire 4,800 x 3,000 x 1,500mm work envelope while cutting in fully interpolative five-axis mode. Initially installed with five machines, the FMS now has nine machines served by a 90-pallet Fastems system.

The F-35 Lightning II, which is descended from the Lockheed Martin X-35, is an American family of single-seat single-engine all-weather stealth multi-role combat aircraft. It is being manufactured in three main variants: the conventional take-off and landing F-35A; the short take-off and vertical landing F-35B; and the carrier-based F-35C.
Lockheed Martin is the prime contractor, with principal partners being Northrup Grumman and BAE Systems.

The USA, which is the primary customer and financial backer, plans to buy 2,456 F-35s through to 2044. The aircraft is projected to operate until 2070.