Case Study: Machining Equipment Taking the F-35 fighting jet to incredible heights
Stealth and supersonic. These are two attributes of the most dominant and complex military combat fighter jet in the world: the F-35 Lightning produced by Lockheed Martin.
It takes a single pilot to manoeuvre the 100 million dollar jet, but it takes thousands of Joint Strike Fighter (JSF) partners to construct the F-35 to ensure that pilot has the most superior fighter apparatus in the world. Starrag is one of those partners, with its machines producing a wide range of JSF specialised components from steel, aluminum and titanium.
“Its heart stopping when you attend an air show or are at a stadium when the US military conducts a flyover with the F-35,” said Starrag Chief Sales Officer (CSO) Alexander Attenberger. “We swell with pride knowing that Starrag plays a role in the JSF program, 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 had begun 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 life cycle costs of machining,” said Starrag Managing Director Dr Bernhard Bringmann. The joint work and developments soon evolved into Starrag’s BTP (Big Titanium Profiler) machining centre with pallet sizes of 5,000 x 2,000 mm to accommodate the machining of stringers. Today, 23 BTPs are in production factories in the UK and Australia.
With 1,000 Nm twin spindles and a tool magazine with more than 400 pockets, the BTP 5000/2 simultaneously mills titanium tail fin components of 700 – 800 mm width and just 50 mm thick to tolerances within 30 µm and to surface finish qualities of Ra 1.6 (for five-axis tasks) and Ra 0.8 (three-axis). To ensure those demands are consistently met, Starrag’s quality turnkey solutions include the construction of a machine foundation 2,000 mm deep to ensure sufficient stability.
Even the earliest machines installed are continuing to hold the specified volumetric tolerances — in some cases, maintaining 50 microns across the machining envelope with ranges that extend to 4,800 x 3,000 x 1,500 mm. "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,” said Mr Bringmann.
He added: “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.”
One of a kind
The impressive capabilities of the Droop+Rein FOGS overhead gantry-type six-axis machining centres are also utilised for JSF work, not only for high-speed finishing of dies, but especially for the fixed, fork-type heads with 300 Nm spindle. Starrag continuously developed its revolutionary FOGS models to efficiently rough machining a range of steel and titanium F-35 components using a variety of heads. The six-axis Droop+Rein is the only one of its kind in the world.
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 50 microns over their entire 4,800 x 3,000 x 1,500 mm working envelope while cutting in fully interpolative five-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 program. With parts being manufactured from around the world, the JSF programme required that all of them meet very stringent tolerance specifications for interchangeability in the jets. 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,” said Mr Bringmann. “In JSF’s case, this could mean another 50 years.”
About the JSF program
The F-35 Lightning II 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. The aircraft descends from the Lockheed Martin X-35. Lockheed Martin is the prime contractor, with principal partners being Northrup Grumman and BAE Systems. The US (primary customer and financial backer) plans to buy 2,456 F-35s through to 2044.