|
Other SAE Magazines Sites
|
|
Technology update
Coming to the surface
-
An Airbus A340/500-600 wing in a jig at BAE Systems.
|
BAE Systems' newly opened surface treatment plant for the production of Airbus wings at Broughton in the UK is believed by the company to be the largest fully automated facility of its kind in the world. When the facility was conceived in 1997, the company decided that a key element in speeding and smoothing its design and development phases would be the extensive application of simulation. Wings for every variant of the expanding Airbus family are built at Broughton, and a new anodic plant was needed to prevent the process from becoming bottlenecked. But BAE Systems wanted more from simulation than just "what if?" scenarios, so an evolving sequence of simulation models was built using the Lanner Group's WITNESS software to optimize layout and operation of the proposed plant. The software was in effect used as an animated event-based CAD tool. The contractor's working drawings were derived directly from the final model. BAE Systems regards the system as driving manufacturing simulation to "the limits."
The anodizing process is used to prevent corrosion of wing components including spars, ribs, stringers, and skins plus a variety of smaller items. The metallic components are given a protective oxide coating to seal the material against corrosion. The parts are first prepared for the anodizing by a sequence of pre-treatments interspersed with water rinses. They are then immersed in chromic acid and heavy electrical currents are applied, the duration and density of which being variable. This is followed by 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 m long, which dictated the length of the tanks when the facility was set up. The complete plant in its purpose-constructed building measures 100 x 50 x 23 m.
An Airbus A340 wing is removed from the build jig at BAE Systems, Broughton.
|
Jim Cruise, Simulation Specialist
at BAE Systems' Airbus Division,
developed the sequence of WITNESS models. 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 from 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 that involved "at least one unproductive blind alley."
The main contractors, Haden Drysys International Ltd., were also closely involved at 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, stated Cruise. An example concerned the use of cranes. Although the utilization of an overhead crane would be quite low, it quickly became apparent that two cranes would be needed for servicing the tank line. Particular focus was placed on the area of the tank line to be traversed by each crane and the mode of "handshaking" and load transference between them. The cranes then had to be linked to the existing system of 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), the jigging operation (whereby electrically conductive suspension media are clamped to the components), and the elaborate control system, which had to ensure the cooperation of all the cranes plus other elements of the system. These issues had to incorporate a look-ahead feature to ensure components were not blocked in acid tanks due to the cranes being used elsewhere.
The control system was developed by modeling the control computers within the WITNESS environment and developing programs for them 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 real-world control software. Jim Cruise regarded this as a crucial part of the process and referred to it as "closing the link" between the conception and the actuality. In more prosaic terms, it gave "grounds for optimism" that the facility really would perform as intended, which it does. An added benefit came from the continued use of the finished model as a module or "black box," which could 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 centers is also taking place. When developing support systems and loading
strategies for these, the company says it finds it extremely useful to have a model of the resource 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 the then-Civil Aircraft Division of British Aerospace. Cruise's involvement dates back to that period. "I regard 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," he said. "We are not taking objects that have already been designed and simulating their movements in space to see how they will work, we are creating the design within the simulated world, then passing it to the CAD team and saying, 'We know this will work, now go
and flesh it out to produce the working
drawings.'"
"Similarly with the control system," he continued, "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."
Stuart Birch
Aerospace Engineering July 2000
|
|
|
