Manufacturing Technologies: UK firm leading the way in metalforming

A small British manufacturer is, literally, at the leading edge of metalforming technology, finds Malcolm Wheatley.

You don’t have to look too far to see politicians queuing up to urge British manufacturers to develop and export worldbeating technologies. Take a look at specialist machine tool manufacturer Group Rhodes, though, and you’ll see a business that has long prospered by doing just that. Managing director, Mark Ridgway, explains that the latest ‘trend’ for high tech exports is nothing new to him.

The SPF process can join metal in a way that eliminates manpower, increases strength and reduces weight
The SPF process can join metal in a way that eliminates manpower, increases strength and reduces weight

“Last year, we shipped the biggest press of its type to China, costing over £2 million,” he says. “And this year, we’re shipping an even bigger one.” Some well established end users, Mr Ridgway adds, include a clutch of upmarket motor manufacturers such as Aston Martin, Bentley and Morgan Cars, as well as defence contractor BAE Systems and aeroengine manufacturer Rolls-Royce.

“Last year, we shipped the biggest press of its type to China, costing over £2 million, and this year, we’re shipping an even bigger one” – Mark Ridgway, Managing Director, Group Rhodes

All of which provides a clue as to the function of the presses in question: creating structures which are strong, lightweight and fastener-free.

But what is the technology supplied by Group Rhodes that has all these companies hooked? Superplastic forming and diffusion bonding, combined into a single powerful process. The Trent engine used on the giant A380 Airbus, for instance, includes fan blades manufactured on Group Rhodes presses.

“Molecular bonding is the strongest join known to man,” says Ridgway. “There’s no compromise: it eliminates riveting, bonding and welding, reducing assembly costs and reducing weight. And we’re one of the just three companies in the world with the capability to produce the equipment that does it.”

Mark Ridgway, Managing Director, Group Rhodes
Mark Ridgway, Managing Director, Group Rhodes

Why such an exclusive group? It’s not an easy trick to pull off, stresses Group Rhodes technical director Peter Anderton, acknowledged as a world authority on the technique.

Explaining how the process works and what it involves, Anderton chooses his words carefully, eschewing complex structures such as the canard wing of the Eurofighter for the homelier example of a titanium hot water bottle.

“Imagine two sheets of titanium, in the shape of a hot water bottle, pressed against each other,” he says. “The sides lying against each other are coated with boron nitride, with the boron nitride delineating the surfaces that you don’t want joined together. Now apply a pressure of about 50 bars, and heat to 925ºC: the parts not coated with boron nitride are now atomically joined together. Insert a nozzle in the ‘neck’ of the hot water bottle, inflate with inert argon gas, and there you go: a titanium hot water bottle.”

Needless to say, customers such as Rolls-Royce and BAE Systems aren’t handing over considerable sums of money for the privilege of manufacturing metallic hot water bottles. And the sums are indeed considerable: while a small 100-tonne press might cost just under £1 million, a larger capacity press might cost four times that.

“Throw in automated material and tooling handling systems, and you’re talking almost £7 million,” says Ridgway. “It’s not cheap, but it eliminates riveting, bonding and welding, enabling manufactures to make a full monocoque structure in one process – and because you’re not drilling holes for rivets or screws, there’s less risk of structural cracking.”

That said, the technology isn’t without its challenges, adds Anderton. Success calls for precise control of a number of critical parameters – which in turn calls for precision engineering of the highest order. Temperatures, for instance, have to be extremely consistent and tightly controlled to within ±2ºC – no mean feat when you’re talking of the temperatures in question: 490ºC for aluminium, 550ºC – 600ºC for aluminium magnesium alloys, and 925ºC for titanium.

Likewise, the argon gas control has to be precise – around ± 15 millibars – in order to deliver the desired deformation characteristics, and the hydraulic tonnage pressure has to be very accurate if a full molecular bond is to be achieved.

Get it right, though, and you’ve got a technique for joining metals together in a way that

Last year, Group Rhodes shipped the biggest press of its type to China, costing £2 million, and this year, they're shipping an even bigger one
Last year, Group Rhodes shipped the biggest press of its type to China, worth £2 million. In 2012 the company will ship an even bigger one

eliminates manpower, adds strength and rigidity, and reduces weight. Typical savings, says Anderton, are around 30% in cost, and 20% in component weight.

What’s more, he adds, the simplistic two-layer hot water bottle analogy doesn’t do justice to the full potential of the technology.

Add a third or fourth layer, he explains, and you’ve got something conceptually similar to corrugated cardboard, with the intermediate layers contributing further strength and stiffness. It is just such additional layers that lie under the skin of the canard wing of the Eurofighter, and the exhaust bay doors of the Joint Strike Fighter, for instance.

So what sort of business develops and masters such technology? Headquartered on an eight acre site in Wakefield, with over 15,000 square metres of factory space under cranage, Group Rhodes is very much a classic British small company, explains Ridgway – albeit one with a lengthy aerospace heritage, as well as a clutch of well-known metalforming brands, including John Shaw, Fielding and Platt, and Joseph Rhodes.

“From the early years of aircraft production, Group Rhodes companies have offered world class expertise in the supply of metalforming solutions,” says Ridgway. “Today, our machinery produces precision engineered components for leading aerospace manufacturers worldwide.” And, what’s more, the business has been involved with superplastic forming and diffusion bonding from its earliest commercialisation in mid- 1970s, when material analysts in the aircraft industry were investigating the phenomena of superplasticity in aluminium and titanium alloys.

For although the size of the business is modest – just 230 or so employees spread over four sites – all major research and development work is conducted in house. And Ridgway stresses that new designs of metalforming machinery are constantly being developed to meet evolving technical requirements.

In addition, he notes, the business works closely with local university departments in design, manufacture and engineering management, mechanical engineering, and a number of global industrial manufacturing companies.

“Britain’s aerospace and automotive industries are major exporters, and critical to the British economy,” sums up Ridgway. “If Britain is to remain competitive, it’s vital that companies like ours grow and prosper, and continue to develop world-beating technologies.”