22 June, 2018

New welding process for jet engines of the future

20 August, 2009

By Rebecca Gunn, Marketing & Sales UK, Moog.

When a world-leading developer of advanced manufacturing processes decides to develop friction welding to a point where it can be viable for securing the blades on jet engines, it stands to reason that any partners it chooses will have a similarly robust pedigree. Aiming at producing a machine that would be the biggest in the world and change your business out of all recognition, you know from the outset that the people with whom you find yourself in harness are going to need matched abilities and complementary skills. Joining forces with such a partner will give you confidence that the result of the project will be more than the sum of its parts.
That’s exactly what happened when UK firms, Thompson Friction Welding (TFW) in the West Midlands engaged Tewkesbury-based Moog to work towards the production of the world’s largest linear friction welding machine. The machine in question is the E100, based at the Thompson facility at Halesowen, West Midlands. The key challenge faced by its developers was that never before had the friction welding technology been used with such required accuracy at the high frequency. The desired specifications for the finished product were:
•           Power 2 MW > 4,500 l/min @ 280 bar (1,188 USg/min @ 4,061 psi) for a weld time of up to 5 seconds.
•           Oscillating actuator capable of moving the tooling and component masses.
•           Frequency up to 100 Hz.
•           Displacement up to 5.0 mm (0.197 in.).
•           Positioning accuracy 13 μm (.0006 in.).
•           Forging force 100 tonnes (220,000 lb).
TFW has been developing advanced manufacturing processes for a wide variety of industrial components for more than 40 years. In that time the company has supplied more than 550 machines worldwide, and has established an enviable track record of bringing friction welding process innovations to market – mostly rotary friction welding techniques and machines. But rotary techniques are not suitable for all components, so the development of this impressively proportioned linear machine was the logical way forward when the TFW people were deciding several years ago how to expand the business. To begin with, TFW bought a company specialising in linear friction welding, and that was the company’s route to market in terms of credibility, making sure that the Thompson name was linked to that process. Then TFW looked for a team of people who could design and build the proposed piece of kit. What was needed was expertise in servohydraulic systems, and hydrostatics. Trawling the marketplace, including a linear friction welding company in the US, eventually led to ‘a shortlist of one, and it was Moog,’ explained TFW managing director Alan Shilton. It was clear from the start that the two companies gelled; they had similar philosophies. “As a business, Moog was up for the work,” said Shilton. “They were positive in their reactions to our questions, while other people in the marketplace shied away from the questions that we were asking. They were open and honest about what they knew and what they didn’t, and we moved forward on that basis. And here we are, two and a half years later, with a machine.”
The E100 demanded a high performance servo hydraulic system, which is very much in line with Moog’s expertise. So what Moog brought to the table included:
•           Multiple Moog servovalves with fieldbus interface, which operate at high flow and high frequency to make the weld.
•           High response Moog closed-loop control system, in other words advanced digital control techniques that achieve the required control over the weld process.
•           Hydraulic power unit, which provided the high power source needed to feed the system.
•           Multiple banks of accumulators, which provide the very high peak oil flow required for the weld.
•           Manifolds and distribution pipe work installation, a comprehensive sub-system routing oil to multiple active components.
Thompson and Moog were clearly the key drivers of the E100 project, but the programme itself was a triumph of collaboration between several parties. The list of partners included:
Thompson Friction Welding - Friction welding process and mechanical/electrical design of machines.
Moog in Germany
Development of high performance digital servovalves with fieldbus interface (D674 Series).
Moog in The UK
- Consultancy, mechanical design of motion system, design of power system, dynamic modelling and sizing of application.
- Load testing of D674 Servovalve for 2 million cycles.
- Design, program and development of the Moog Modular Multi-Axis.
Programmable Motion Control Servodrive (MSD) high speed closed loop duplex system.
- Integration of MSD control. x3 MSD.
- Full program management of servo hydraulic system build and Hydraulic Power Unit installation.
- Development of high speed closed-loop communications for EtherCAT servovalves, equipped with fieldbus interface (EtherCAT), sensors and analogue and digital I/O modules. High speed industrial fieldebus systems have been used for communications between the Moog real-time controllers and the TFW overall control and monitoring systems.
It is clear that Moog’s experience and expertise in project management, design, development, manufacture, installation and support services have all contributed to the success of the project. But the company’s own practical capabilities in the friction welding process – as well as in high performance servo hydraulic control, high performance hydraulic actuators and the provision of large scale hydraulic power plant and distribution systems – are second to none. Moog’s own presentation on the project ‘recipe’ underlines the technical scope of the project: Take the oscillating flow of three ‘turbo charged’ Moog D674 Valves (all 6,000 lpm of it), meaning that four valves would deliver a total flow rate of 6,000 lpm and add the squeezing force of two hydraulic actuators .Connect it all together with a sophisticated pipework and manifold installation, then the intelligence of three Moog Servo Controllers (MSC controllers) and near to 100 sensors. Bind together with the know-how of Moog application expertise, bake for five seconds at 2,000,000 watts and let cool. Repeat for another 50,000,000 cycles.
“People expect to see one single tool or machine when we talk about it – in fact, it’s a facility, not just a machine,” said Shilton. “Its 100 tonnes capacity (110 ton US or 220,000 lb) and two and a half metres height (8ft 2½ inch) means that it’s huge compared to previous existing machines (just 70 tonnes, 77 ton US or 154,000 lb) so this is much larger and everything else that goes with it has that sort of scale. That was our intention from day one – it’s not something that has just come about. We set off knowing that it was to be the largest and most flexible machine ever built. We are very close to making our first weld, which will be a titanium product to start with. We’ll begin with a qualifying programme, and then we will put it through its paces – from the very small through to very large (100 tonne) jobs. The smallest is 800 mm2 (1.25 sq. in.), and the largest surface area that we are able to weld is 10,000 mm2 (15.5 sq in).”
Shilton continued: “It’s a development project, the net result of which is the production of a machine. Throughout the process, Moog has been very accommodating in terms of delivering what we requested of them. We had broad criteria because we set some ground rules at the start, and we had all the tooling, special frequencies of amplitude we wanted the machine to perform at. We depended on Moog to deliver that end result, and they have not been found wanting. It became more of a partnership as each stage progressed; the senior people are fully aware of what we are doing in the marketplace because we keep them informed. They know where our plans and aspirations lie in relation to the marketplace. We are not just in jet engine manufacture – we have come up with a number of novel ideas for using linear welding as a process. One of the key motivators is the belief that the E100 machine will alter the way in which jet engines are manufactured. It will be five to ten years down the line, because in the aircraft industry you have to look a little further ahead than in, say, the automotive industry. That’s one of the things we have learned along the way: new processes need to be maturated, you need to be comfortable with the process.”
Shilton concluded: “We have had some exciting and interesting times but it’s always been great. We already have two orders to work on, on a machine that’s not yet been finished, which confirms our belief that the marketplace is ready. It’s all very exciting. We hope it’s something that will change this business out of all recognition and put us in a prominent position for attacking the worldwide market, not just the UK. And we’ll be hand-in-hand with Moog all the way.”
Pic caption: Exterior of E100 machine body in partial build, showing forge and tool assembly on the main slide.

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