Interface Management of ALCAS Wingbox Cover

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Interface Management of ALCAS Wingbox Cover
Fettling of Rib Feet to Maintain Interface with
Wingbox Upper Cover
Author Jody Muelaner
INTRODUCTION The Advanced Low Cost Aircraft
Structures (ALCAS) project has the objective of
reducing the weight of an airliner wing by 20
while also reducing the cost of manufacture
compared to a metallic wing. The demonstration
lateral wing box is being assembled by Airbus in
the UK. LIMA has worked with Airbus in the UK to
develop a number of innovative metrology assisted
processes to realize the ALCAS objectives. A key
area of interest was the interface between the
wing box ribs and the upper cover. The cover was
produced using a resin infusion moulding
technique. This produces the panel structure on a
single sided mould with the outer aerodynamic
profile tightly controlled, this is known as the
outer mould line (OML). The inner profile which
must interface with the spars and ribs is formed
using a vacuum bag and is therefore not tightly
controlled, this surface is known as the inner
mould line (IML).
Innovative techniques for the modelling of
metrology enabled processes have been developed
at the University of Bath and these were deployed
in the modelling of this process. These
techniques model the combined uncertainty of a
complete process combining process variability
with measurement uncertainty. Analytical
uncertainty evaluation and Monte Carlo simulation
are used to propagate these components of
uncertainty to determine the combined process
uncertainty. TEST PROCEDURES LIMA also worked
with Airbus in the UK to design and carry out
experiments. These were used to evaluate the
components of uncertainty within the process such
as the uncertainty of measurement of systems
measuring the cover IML, datuming the robot
within the wing geometry and providing positional
feedback to the robot. Positional feedback was
provided by the Adaptive Robotic Control (ARC)
system which is an Airbus patented process. The
variability of the machining process its-self was
also an important contributor to the combined
uncertainty of the process.
Uncertainty Evaluation for Interface Management
of Wingbox Cover to Ribs
LIMA supported the development by Airbus in the
UK of a process to machine the wing box ribs
during assembly to fit to the uncontrolled cover
IML. This required accurate measurements of the
cover IML to be made and for a flexible
industrial robot to datum its-self and machine
the rib feet with respect to these
measurements. The first phase of the work carried
out by LIMA was to model the uncertainty of the
complete process in order to provide advice on
process optimization and predicted capability.
Experimental Design for Robotic Machining Under
Closed Loop Control
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PROJECT PARTNERS
PROJECT BENEFITS The use of uncertainty
evaluation and designed experiments has enabled
an efficient process to be developed with a high
level of confidence in the final capability. This
has been achieved before significant costs were
committed to the final process. ASSOCIATED
PUBLICATIONS C. Ferri, J. Muelaner, et al.
(2008). Rib foot fettling in wing skin assembly.
Bath, The University of Bath 75. Technical
Report produced for Airbus in the UK.

• LIMA The Laboratory for Integrated Metrology
  Applications
• LIMA is based in the Innovative Design and
  Manufacturing Research Centre (IdMRC) within the
  Department of Mechanical Engineering at the
  University of Bath.
• LIMA is an independent centre of excellence for
  collaborative research and delivery of innovative
  metrology enabled applications, integrating
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  with industrial applications to develop new
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  working solutions and training staff in
  metrology technologies for medium to large scale
  manufacturing.
• LIMA carries out-
• RD in metrology and measurement assisted
  automation
• Verification of instruments and complete
  metrology enabled processes
• Metrology application consultancy
• Delivery of complete solutions
• Measurement services providing instrumentation
  and expert users
• Training of customer staff

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Applications Department of Mechanical
Engineering, University of Bath, Bath BA2
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