Encoders Guide Superjumbo Wing Assembly
The new Airbus A380 Superjumbo, now under construction in Europe, is the largest commercial aircraft in the world. With 555-passenger capacity, and a wingspan in excess of 260 feet, building the giant double-decker calls for highly innovative assembly techniques. These include use of several wing-panel assembly machines that have linear encoder systems for positioning accuracy.
The new Airbus A380 Superjumbo, now under construction in Europe, is the largest commercial aircraft in the world. With 555-passenger capacity, and a wingspan in excess of 260 feet, building the giant double-decker calls for highly innovative assembly techniques. These include use of several wing-panel assembly machines that have linear encoder systems for positioning accuracy. The four machines, which are each four-stories-high and weigh 80 tons, incorporate more than 1 km of 40-micron scale tape to determine precise position of traveling yokes. The machines straddle each skin panel on the Superjumbo wing to drill, tap, and rivet stringers along the entire span.
Electroimpact Inc. has worked with Europe's Airbus Industrie to deliver equipment for wing assemblies for the Airbus A320 family, the four-engine A340, and now for the huge A380 wings. The company has used Renishaw encoder systems for each of its Airbus wing assembly projects, in part because the tape scale used in Renishaw's RG4 linear encoder system is available in continuous roll form.
Thousands of holes
Designated LVERs (low voltage electro-magnetic riveters), the huge twin-towered yokes of the wing assembly machines, run on beds capable of supporting all 16 wing panels involved. Each head must drill thousands of holes and apply all rivets and bolts as it traverses the stringer/skin combinations. The heads always must be perpendicular to the skin surface and therefore have to adjust to match any combination of camber, aerofoil contour, dihedral, taper, and sweepback anywhere along the wing.
Fundamental to this process is the complex CNC riveting/drilling head, which depends upon the linear accuracy, span-wise, of the yoke structure as it picks up signals from the RG4 linear encoder system.
The RG4 is an open, non-contact optical system, which is designed to eliminate friction and wear for high-speed, high-resolution operation. The encoder system has a range of compact read-heads offering resolutions from 0.1 to 10 micron, speeds in excess of 10 meters per second, and industry standard outputs. It is compatible with Renishaw's RGS40 tape scale. Supplied on a reel, the self-adhesive, flexible scale is cut to the length required and fitted in-situ along the full traversing distance of the 160-meter machine.
An infrared LED shines light onto the angled scale facets where it is directed back into the readhead through a transparent phase grating. This produces sinusoidal interference fringes at the detection plane within the readhead. The optical scheme averages the contributions from over 40 scale facets and filters out signals not matching the scale period. Because thermal characteristics often play a significant role in determining overall measurement accuracy, the RGS40 scale is restrained at the ends and is therefore forced to match thermal behavior of the substrate, removing the need to compensate for another coefficient of expansion.
The automated fastening cells supplied by Electroimpact offer a 40% space reduction compared to earlier riveting systems and save time and labor by eliminating the need to first manually tack components and then split them for deburring before re-tacking.
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