| Jaguar Cars is making increasing use of the
latest rapid prototyping (RP) technologies at its Whitley Engineering
Centre in the UK to speed the development of new vehicles by making plastic
parts directly from CAD models, therefore eliminating the expense of producing
mould tools. A leading role is being played by laser-sintering machines
from EOS, which create prototype trim and even engine parts from nylon
powder (polyamide PA2200) by fusing them layer by layer into their respective
shapes.
The Jaguar XJ prototype
bumper section was built from two pieces, each laser-sintered
from nylon powder in the EOSINT P 380 machines |
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Close-up of the laser-sintered prototype
bumper section for the Jaguar XJ. The painted model was
used to visualise the fit and finish of key components prior
to production
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The resulting components, such as the air intake manifold, door inners,
fascia substrate, interior air vents and exterior light housings, are
robust enough to be used on test vehicles running around the track, allowing
more data to be collected early on in the development process. By contrast,
other rapid prototyping techniques that employ such materials as epoxy
resin and ABS produce relatively fragile parts that are best suited to
visualisation.
Take the V8 air intake manifold prototype for a forthcoming Jaguar car,
for example. In the past, hundreds of thousands of pounds would have been
invested in hard tooling for its manufacture. Following every design change,
it would have cost thousands of pounds to alter the tool, a process which
took several weeks each time. If the changes were substantial, a completely
new tool might be needed.
Using laser-sintering RP technology, two design iterations of the manifold
were produced and 17 were subsequently built in nylon for less than a
thousand pounds each and in a lead-time of one and a half days per manifold.
It represented an enormous financial saving in the development of this
vehicle component alone and has halved the time needed to perfect it from
one year to six months.
The RP department Whitley is run as a profit centre within the Premier
Automotive Group (PAG). It regularly receives work in the form of STL
files from a number sources within the group, primarily the design, aerodynamics,
body, chassis, electrical, power train and engineering departments within
Aston Martin and Land Rover, in addition to Jaguar.
The Engineering Centre started using RP in 1997 to build parts in layers
using STL files extracted from CAD models. Among the components produced
were small models of complete vehicle exteriors for visualisation and
detailed scale models of structural parts for wind tunnel tests.
By 2000, however, it became clear that a further RP technique was desirable
– one that allowed robust parts to be produced that would withstand
the rigours of functional testing. This is where laser-sintering comes
into its own. The company installed two EOSINT P 360s, later upgraded
to P 380 performance by the addition of new software and hardware that
gives an even better component finish and up to 30 per cent faster build
times.
One of the first jobs run on the machines was a door assembly model for
the XJ saloon. It was used as a robust development aid around which the
shape of the protective security shield for the car door could be developed
in advance of production parts. The model stood up well to the task, whereas
a similar part produced using stereolithography (SLA), for example, would
have been too brittle.
A larger, laser-sintered component for the same vehicle followed, namely
a bumper section built in two pieces that was used for visualising the
assembly of key parts such as the exhaust pipe and tow eye fixing. The
aesthetics of this part of the vehicle could therefore be evaluated before
progressing to hard tooling.
The EOSINT P380s currently operate 24/7 at the Whitley Product Development
Centre, producing within its 340 x 340 x 620 mm build envelope a myriad
of PAG parts, for which the STL files are managed in a database with scheduling
capability. Parts are positioned using Magics software from Materialise
for optimum use of the build volume. Jaguar's experience has been that
the throughput of laser sintered parts exceeds that of other RP processes,
as the entire build volume can be filled with parts whereas with the other
processes it operates, parts may be fitted within the area of the build
platform only.
The nesting flexibility afforded by the EOSINT P380s makes it easy to
incorporate dozens of parts in each sintering cycle. An interesting component
that is regularly added around other parts is not a prototype at all,
but a complex plastic assembly aid that assists operators working on the
recently revealed XK coupé and convertible to position the window
lift mechanisms during build. A stock of 3,000 of these parts was required
by the manufacturing plant, as once fitted, the assembly aid remains on
the vehicle throughout the build process. By August 2005, around half
of the parts required had been produced on the P 380s as fill-in jobs,
without the need to invest in expensive plastic injection mould tooling.
As to the future, Jaguar expects to see rapid prototyping quickly develop
into rapid manufacturing processes, initially capable of satisfying niche
requirements. In the more distant future it is possible that today's RP
processes hold the key to the next generation of volume production technologies
where the design constraints, tooling and inventory overheads of today's
processes might be eliminated. It is certain that Jaguar will continue
to produce plastic components for prototype and niche applications such
as the window lift assembly aid, following the success of the XK window
tool project.
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