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Typically, deflection and running
accuracy of linear guides and ball
screws add errors. To minimize
deviations, several sizes and
styles of Rexroth runner blocks
and guideways were specified,
Instead, Electroimpact devised
a multi-arm manipulator to
maintain the panel’s proper form
and provide precise positional
control while presenting the panel
to the wing structure for fastening.
The Stage 01 structural-wingassembly
process is more labor
intensive than the Stage 00
operation. The assembled skin
panels are positioned by the
manipulator into four-story high
jigs, which contain other wing
parts — ribs, spars, leading and
trailing edges. For the upper
wing, a combination of mobile
drilling machinery (HAWDE)
and manpower accessibility is
required over the large surface
area of the upper wing panels. For
the lower wing, holes as large as
1.25 inches in diameter are drilled
for bolting the lower wingskins to
undercarriage reinforcements.
Starting at stage 00:
wing-panel assembly
To manufacture skin panels,
Airbus U.K. and Electroimpact
teamed up to create a highly
automated facility.
According to Hempstead, “We
faced several challenges in this
program, namely how to bring a
fixture of stringers and machined
skin panels together in a precise
build configuration, while an
automated machine tool fastens
the components into a skin panel
assembly. At this stage, speed,
accuracy, and operator safety are
critical to this success.”
Each wing surface is comprised
of five panel assemblies, 20 panels
total. The Airbus Stage 00 facility
produces 16 of these panels.
Traditionally, these panel
assemblies were built on manual
jigs, requiring many skilled
workers to locate and drill
holes, pull components apart for
deburring and cleaning, apply
sealant, and insert two-piece
lockbolt fasteners. Panel assemblies
were then transported to a
riveting machine for final rivet
installation. Production rates
were limited by the number of
jigs in production, worker access
and speed, and hole quality and
rework requirements. Finished
panel quality was also limited
by how well the fixture held the
components in proper contour.
But Electroimpact believed there
was a better way. “Building on our
previous work for the Broughton
facility, we ended up expanding
the system’s performance
envelope and accuracy of earlier
panel production machinery,”
says Hempstead. “The result is
a new generation of wing panel
Massive, multi-arm manipulator maintains
proper wing-panel shape during transfer
to the Stage 01 jig.
because they provide excellent
performance on several axes.
Highly pre-loaded roller runner
blocks, pre-loaded ground
ball screws, and caged-ball
runner blocks were employed,
because pre-loading ensures
rigidity of the system and
thereby maximizes accuracy.
“We’re designing the machines
and fixtures concurrently with
the wing design,” says Hempstead.
“Consequently, some aspects of the
design cannot be completed until
late in the program. That means
schedules and lead times are tight.
Fortunately, we’ve been supported
every step of the way by Rexroth.
“Accurate estimation of vendorsupplied
product lead-time is
critical in keeping assembly on
schedule. I’m happy to say that
since operation began in March
2003, the Stage 00 facility has been
producing assemblies on time and
with far better speed, quality and
points is very difficult. “Basically
you have a statically indeterminate
system. The panels will twist, bend,
and kick as they react to the forces
introduced by lifting equipment.”
“To overcome this problem,
two of the six arms control the
vertical position of the panel,” says
Karagias. “The other four arms
act as slaves imparting a constant
programmed force upon the
wing panel. That way, when the
positioning arms are commanded
to move either up or down, the
load-seeking arms follow along to
maintain the panel’s form.”
Len Hathaway of Pacific
Power Tech, Seattle, WA, was
instrumental in assisting the
Electroimpact team to specify the
Rexroth hydraulic components
for the project. The primary axis
of movement is maintained in
closed-loop servo control by a
　
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