BAe simulates operation of new plant with CAD

BAE Systems has used Lanner Group's Witness simulation software to play a key role in the development of a massive new £21 million surface treatment plant at its Broughton Airbus factory.

BAE Systems has used Lanner Group's Witness simulation software to play a key role in the development of a massive new ?21 million surface treatment plant at its Broughton Airbus factory.

The plant is believed to be the biggest fully automated facility of its kind in the world.

The Witness program was used to provide more than traditional 'what if ?' simulation.

An evolving sequence of simulation models was built to optimise the layout and operation of the proposed plant, the software being used in effect as an animated event based CAD tool, and the contractor's working drawings were derived directly from the final model.

According to BAE Systems, this is driving manufacturing simulation "to the limits".

BAE Systems' plant at Broughton near Chester manufactures wings for the Airbus family of airliners, which is currently enjoying remarkable success.

Every wing for every variant of the expanding Airbus family is built at Broughton.

Faced with an accelerating demand for the current range, together with new models under development, BAE Systems decided to install a new anodic treatment plant to forestall the process becoming a bottleneck to production.

The anodising process is used to prevent corrosion in wing components such as typically spars, ribs, stringers and skins, together with a variety of smaller components.

The components are immersed in tanks of chromic acid and heavy electric currents are passed through them.

This causes a protective oxide coating to be artificially grown onto the metal surface, sealing the underlying material against corrosion.

The parts are prepared for anodising by a sequence of pre treatments interspersed with water rinses, and then go into the chromic acid, the duration of immersion and the density of the current being variable, following which is a sequence of rinses to remove the acid and final drying by hot air.

Twelve tanks are involved and each component goes through the sequence twice: once immediately after machining to provide temporary protection and to assist in flaw detection, and again immediately prior to painting.

The largest wing skins are 34 metres long, which dictated the length of the tanks.

The complete plant in its purpose made building is 100 metres long by 50 metres wide by 23 metres high.

The sequence of Witness models was developed by Jim Cruise, Simulation Specialist at BAE Systems' Airbus Division.

Starting with the only known quantities being the sequence of dips and the number of loads to be processed each day - and taking inputs from engineering, operations, facilities and laboratory personnel as well as potential suppliers and contractors - the Witness software with its interactive animated display was used as the focus for a series of brainstorming meetings.

These took place over a period of months, a process which involved at least one unproductive blind alley.

The main contractors, Haden Drysis International Ltd, were also closely involved from an early stage.

This cross company and cross discipline dialogue, with the consequences of suggestions and changes readily seen on the PC screen, was extremely effective, Jim Cruise claims.

He believes that the understanding gained could scarcely have been obtained in any other way, and certainly nowhere near so quickly and with such a high degree of confidence.

For example, although the utilisation of the overhead crane servicing the tank line is quite low it rapidly became apparent that two cranes would be needed.

Much discussion centred on the area of the tank line to be traversed by each crane and the mode of handshaking and load transference between them.

These cranes then had to be linked to the existing system of overhead cranes in the main factory building, which operate at a lower elevation.

Further issues concerned the handling of the flightbars (girders from which the components to be treated are suspended, and which in the final design also serve as lids to the active tanks), the jigging operation (whereby electrically conductive suspension media are clamped to the components) and the elaborate control system which had to ensure the co operation of the various cranes and other elements of the system.

This had to incorporate a look ahead feature to ensure components were not blocked in acid tanks due to cranes being busy elsewhere.

The control system was developed by actually modelling the control computers within the Witness environment and developing programs for them (still within Witness) that produced the required operation of the model.

These programs were then taken out of WITNESS and handed to the programmers who were to write the control software in the real world.

Jim Cruise sees this as a crucial part of the pWitness rocess and refers to it as "closing the link" between the conception and the actuality.

In more prosaic terms it gives grounds for optimism that the facility really will perform as intended, as has happily proved to be the case.

A final benefit comes from the continued use of the finished model as a module or 'black box' which can be incorporated into other simulations.

The treatment plant is only one of a number of major developments at BAE Systems Broughton; heavy investment in advanced long bed machining centres, for example, is also taking place.

When developing support systems and loading strategies for these BAE Systems found it extremely useful to have on hand a model of the portal into which their output will be directed.

The anodic plant model was being incorporated into other wider simulations months before the real plant was commissioned.

BAE Systems' use of Witness dates back to 1988 when the package was chosen as the standard for use within the then Civil Aircraft Division of British Aerospace.

Jim Cruise's involvement dates back to this period also.

He regards this particular exercise as noteworthy on two counts: the use of a simulation tool as first draft CAD with a time dimension and the concurrent development of the control system.

"We're not taking objects that have already been designed and simulating their movements in space to see how they will work," he says.

"We're creating the design within the simulated world, then passing it to the CAD guys and saying 'We know this will work, now go and flesh it out to produce the working drawings.' "Similarly with the control system: we're passing our simulated controls to the programmers and saying 'we know this logic will drive the plant to best advantage, now put it into your computers.' "Manufacturing simulation is powerful technology and BAE Systems is driving it to the limits.".

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