Air conditioning

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Airbus flies in the face of tradition with the introduction of automated wing production lines for airliners and military transports. Stuart Nathan reports.

As mass production techniques and robotics have been with us for over a century, it's natural to think that many of the machines we see around us are themselves made by machines. Most of them, however -even the most technologically advanced -still rely on humans to build them.

At Airbus, wings are among the components which are still made mainly by hand. This is about to change, however, with automated systems being put into place on the production lines for airliners and military transports.

The automation is a result of a long-running collaboration between Airbus and product lifecycle management (PLM) software developer Dassault Systèmes. Among the aircraft to benefit from the new systems will be the narrow-body A320 airliner, and the A400M military transport aircraft.

Scheduled to replace the Hercules transport in many European airforces, the A400M was the first Airbus to be designed entirely using CATIA software, also developed by Dassault.

The new automation system is built around another Dassault product, DELMIA V5 Robotics. According to Rob Lloyd, engineering group leader at Airbus's UK wing manufacturing facility in Broughton, Cheshire, the automation will reduce the time needed for a complex task, drilling holes in wing skin panels for the A320 prior to fitting the strengtheners, or stringers, which reinforce the wing.

'The typical wing skin is a sheet of aluminium, stepped up in thickness, pocketed and faceted to give it strength, and stringers are bolted to the back of it lengthwise, to give it structural rigidity,' he explained. 'Traditionally, this operation on the bottom skin has always been a manual operation. We built the stringers into a jig, lay the skin on top of it, put templates on top of that, and drill through the templates manually. What we're introducing now is a robot to take over that operation.'

The system uses a robot-controlled drill, sitting on a cart which can move up and down the length of the wing. This is controlled by FasTIP software from CENIT, a technology partner of Dassault. 'This gives us real-time control of the robot, but also simulation of the robot in space and all the components,' said Lloyd. 'We've got full clash detection, and we can do much proving off-line so we don't have to tie up the jig.'

Lloyd added that this is proving to be very different from previous experience with robots and software control, because the type of movements and the complexity of tasks are more demanding than the usual ones delegated to mechanised systems. 'Robots are usually used for very repetitive pick-and-place type tasks. They do this particular motion 20 times a minute, so the programming system doesn't have to be all that exact -you can teach the robot in situ,' he said. 'Whereas with our system, we're trying to get the robot to go to 8,000 different positions per wing skin panel.'

The simulations within the DELMIA system, therefore, come in very useful, allowing Lloyd and his staff to see where the robot is at any time in the programming. 'You can stop the simulation at any time and control the robot with the mouse in any direction,' said Lloyd.

Some manual work is still needed, because the robot only works on one side of the skin panel. 'The robot will drill holes and insert a slave bolt or dowel to stop the components moving around, so you still need some manual intervention on the furthest side of the panel from the machine. An operator has to go around and put a nut on the slave bolt.'

Moreover, said Lloyd, there is a trade-off with robot versus manual drilling. 'It should save on people and reduce the cycle time it takes to drill the whole panel off. But with the manual system, if you're in a hurry, you can throw 20 workers at the jig. So we've still got that option if we need it -we can just park the robot and go back to the manual jigs if we really needed to.' Airbus's current estimates envisage savings of 68 man hours per wing set with the new automation system, said Lloyd.

In the case of the A400M, the system is slightly different. US aircraft assembly tooling specialist ElectroImpact has supplied a large assembly jig for the wings of the new plane, which allows a five-axis machine to drill the holes in the wing skin panels.

The wing jig is a formidable piece of equipment. A 20-tonne, 24m-long retractable beam is mounted on two towers, 5m high at the wing root end and and 2m high at the tip. The beam moves to allow tooling to work on the upper and lower surfaces of the wing and can retract altogether so that wing components can be loaded into place at the beginning of the process, and the final assembly removed at the end.

A single Siemens programmable logic controller operates frequency drives and pneumatic solenoid valves to move the beam, with an operator at each tower needed to operate the retraction mechanism.

Each tooling module corresponds to a key control surface on the wing, such as spoilers, flaps or ailerons, and the tools are positioned so that only short movements are needed for their operation.

The same drilling software is being used for drilling the skin panels on the A400M, but the machinery and the process itself is rather different, said Lloyd, because of the way the wings of the military aircraft are constructed.

'Again, it's a single-sided system which only attacks one side of the wing,' he said. 'But on the A400M we're drilling through a composite panel. There might be carbon fibre, then titanium, then more carbon fibre, or other combinations, but there are two different materials we have to drill through at once. And that necessitates a different drilling speed, otherwise you'd end up with the right-sized holes in the titanium, and a well oversized hole in the carbon fibre.'

The automation system allows the machine to be programmed for different speeds in a single pass. 'We'll just pick an entrance point for the drill,' said Lloyd. 'The software will interrogate the component stack-up and tell the output program that it's, say, carbon fibre for the first 13mm, and titanium for the next 12mm.'

An on-board materials base holds information on the drill speeds necessary for each type of material, and the machinery will automatically adjust feeds and speeds to make the correct sized holes.