Friction is good for Thompson

Queen's Award winning Thompson Friction Welding has put the finishing touches to its new E100, 100 tonne linear friction welding machine. With this, it claims to have set a new record for the largest ever weld, by rapidly joining a 10,000 mm² titanium component, surpassing the previous milestone, believed to be around 5,500 mm². The E100, developed, designed, manufactured and located at Thompson's headquarters in Hereward Rise, Halesowen, is said to be the first commercially-available linear friction welding machine in the world. Other linear friction welding machines have previously been built for in-house purposes by large aerospace OEMs, with the technology highly guarded, and there are only eight linear friction machines operating in the world, claims sales manager Nick Edge. But the linear process, says Thompson, is suitable for use in almost any type of industry, including, of course, aerospace, but also automotive, medical, power generation and other high-quality engineering applications, such as Formula 1 components. Aerospace is a particular target, however, Mr Edge making special note of the welding of turbine blades to turbine hubs, typically in titanium, to produce blisks, as the current top application, hence the secrecy, in fact. But even wider application is anticipated because, with the increasing use of titanium in modern commercial aircraft and with its cost high and availability stretched, welding of parts together to produce larger parts, rather than machining large billets of titanium to produce smaller components, is anticipated as becoming increasingly attractive. "For a blisk manufactured via the friction welding route versus the machining route, the buy-to-fly ratio can be cut from 20:1 to 2:1," Mr Edge underlines. This ratio simply states how much material is bought versus how much ends up flying – and that saving, up to 90 per cent, is highly attractive (the titanium 6AI 4V six months price is currently around $20/kg, down from over $28/kg in January (www.metalprices.com). Blisks are most commonly found on military aircraft. For example, Rolls-Royce employs linear friction welding within the UK, in the manufacture of the LiftFan engine, which supports the vertical take-off capability of the Joint Strike Fighter (Lightening II) – the UK's Harrier replacement. Thompson machines are not employed for this, however. Thompson's E100 was built "to give us credibility", the sales manager explains, with a team including individuals that had been involved with the process previously assembled to undertake the task. This allows the company to develop its own intellectual property and then "sell the process to whoever wants it", rather than develop it with a company and not have control of the IP. The machine is also sized to produce the next generation of blisks, which will be larger than those currently made. The company is, for instance, already working with Boeing – having just received a supplier excellence award – and Mr Edge says: "Boeing is very keen on this technology," adding, "the amount of titanium used on new aircraft is increasing, because composite materials react with aluminium, but not with titanium." The scope for linear friction welding is, ironically, partly being driven by increasing use of non-metals. But aerospace is not yet a large chunk of the company's business. Mr Edge explains Thompson's historical and current strengths, which will continue: "Our main markets are machines for the manufacture of truck axles – single and double-ended machines; hydraulic piston rods, and drill pipe and rods. We are dominant in these three areas. For example, in the axle market, we have a unique machine, which most axle makers in the world use. On hydraulic piston rods, again, we have some very special capabilities. And in pipe friction welding, we are the only company in the world that can weld the full range of API materials – we have sold many of those machines recently. As for drill rods, again we have a unique capability to remove flash off inside the weld, with a method we have developed. " Apart from these particular areas, Thompson also makes machines for other parts, such as drive shafts and air bags – "The process has a lot of applications, we have done a lot of other things," the sales manager offers, and that includes some work already for the aerospace industry, although he is unwilling to give specific details. Image: Friction welding is good at joining dissimilar metals as with these yellow good parts This aerospace work revolves around the use of inertia rotary welding (not the new linear welding technology), a rotary process where two parts/faces are brought together under load and where the weld process itself 'decides' when it will stop, as opposed to direct drive rotary friction welding where one part is rotated against a stationary other, where the machine is programmed to stop at a particular point, and where both length and angular position can be tightly controlled. Previously, the use of inertia rotary friction welding meant that relative angular rotary position between two parts could not be closely controlled, nor was length control good. With newer control technology, developed by Thompson, however, that is not now the case. "Certain materials, mainly aerospace materials, need inertia welding metallurgically, so that the 'freezing' of the weld controls the process," says Mr Edge. Fundamentally, the direct drive friction welding process has these stages: run up to speed; apply first pressure to clean the surface; increase the pressure during the heating phase; stop driving and apply more pressure (reducing length) in a forging type process; the process can be stopped at desired length and angle. The process operates under closed-loop control, with external parameters/setting controlling the process, not the material. With an inertia weld, you get up to speed, increase the force and ram it together with the material stopping the process (both angle and length) upon 'freezing'. "We are now able to control the ramp down; slow the speed down in a controlled fashion, so the difference between the two processes is not so great. The logical outcome will be a hybrid machine able to do both," reveals Mr Edge. Box item Thompson – award winning performance Thompson Friction Welding is part of a group headquartered at Halesowen, which also includes DVA (designs and makes hemming products for the automotive industry) and KUKA Automation + Robotics. In fact, the group, which together have a turnover of £20 million and 87 employees, is owned by German firm KUKA AG, which also has a friction welding activity, although Thompson's machines are of a larger physical scale. Thompson's history can be traced back to a family firm started in the Black Country in 1834 and its friction welding roots go back some 50 years, as part of the John Thompson Group, but the company has been part of KUKA AG since 1993. Four years ago, it acquired a small UK company – Blacks Equipment – that had linear friction welding technology. This has informed the development of the E100. The company has just picked up its first Queen's Award for Enterprise and celebrated the event on 23 July at its Hereford Rise, Halesowen site, where invited guests and employees witnessed the presentation by Her Majesty's Lord-Lieutenant, West Midlands, Paul Chandrasekharan Sabapathy to Nick Edge. Thompson Friction Welding is one of a handful of companies globally that designs and manufactures friction welding machines, both rotary and linear, and has been successfully winning business around the world, hence the award – overseas sales of its friction welding machines have increased by over 160 per cent over the last three years. Indeed, exports are in high 90s, in percentage of turnover terms. First published in Machinery, October 2009