Production
Applied
Engineering
technologies for production engineers
Problem taped
Automation, which for years has been used sparingly in aerospace production,
could take centre stage at GKN. Siobhan Wagner reports
GKN has developed an automated system
it claims will produce carbon fibre
aerospace components up to 40 times
faster than existing methods.
The automated tape lay-up (ATL)
machinery developed by GKN can lay
composite tapes 150mm or 300mm wide at
the rate of about 18.2kg/hour. This
compares with hand lay-up rates of
0.45kg to 1.45kg/hour.
‘If carbon fibre wing spars were made
by hand, the man hours required would
be extremely high,’ said John Cornforth,
head of technology at GKN Aerospace.
‘GKN felt that this product would only be
commercially successful if an automated
method was developed.’
The Airbus Military A400M primary
wing spar — the largest all-composite
wing spar produced — is the first to be
made using the technology. Future parts
could include skin panels or flaps.
The process begins with a bobbin or
roll of material that sits on a multi- axis
robotic head, which moves to the required
position and the compaction roller
touches the part. As the head moves along
the surface the material is fed to the
compaction roller, which presses the
material firmly on the surface.
When the head has travelled the
distance required, an ultrasonic knife
cuts the carbon tape to the required
shape. The excess material is then
automatically put on a scrap pile. This
process is repeated hundreds of times
until a full part it created.
‘The process is rather like
wallpapering, covering a surface
with strips of material in different
orientations,’ said Cornforth.
The ATL then lays the material on to a
flat tool. A separate, drape-forming
process is used to form the part into the
desired shape.
While ATL is excellent in the
production of large, flat structures,
it can cause composite fibre buckling
in more highly shaped components,
such as nacelle cowlings, doors and
engine ducts.
The ATL process
developed by GKN
could pave the
way for further
automated
production within
the aerospace
sector
So GKN is also investigating a
complementary technique —
automated fibre placement (AFP) — to
speed up the production of more
complex shapes.
Cornforth explained that a fibre
placement machine is similar to an
ATL except that instead of using one
very wide band of material it uses
multiple thinner bands. The reason for
using small tapes is that they have
more steer before buckling, which
means they can be driven into a curve.
‘For example, if you tried to lay a
large piece of paper around a football
The paper would start to fold and tear,’
said Cornforth. ‘But if very small strips
of paper were used no buckling or
tearing would occur.’
By using small tapes, very complex
shapes can be manufactured directly
without hot drape-forming. Due to the
small tape width in AFP, no waste
material is created, so the ultrasonic
knife operation is not required.
For years automation has been used
with caution in aerospace production,
with concerns that robots are not as
accurate as manual work.
Yet GKN has claimed parts made
the EnGIneeR 16–29 JUNE 2008 35
with ATL machinery are even more
accurate than those produced by hand.
The 14m wing spars the company
makes now are accurate to within
0.5mm, compared with about 300mm
for the corresponding metal
components they are replacing.
The company said automated
production is also increasing material
quality. During production bubbles can
form inside composites and when the
materials harden it leaves a void, or
imperfection, which can cause weak
spots.
While for most products four per
cent of void is acceptable, GKN claims
to be achieving up to 1.5 per cent.
With these increases in quality and
consistency being achieved automati-
cally, GKN said there could be a time
when it will be unnecessary to inspect
every component post-production.
Cornforth said AFP and ATL
machines are effectively ready to go.
He said manufacturing tool provider
MAG Cincinnati and machine tool
manufacturer MTorres are both
making machines to be delivered
for other applications within the
aerospace sector.
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