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Academic and industry collaboration develops injection moulding technology that could enable
electronic circuits to be embedded directly into car bumpers and roofs. Siobhan Wagner reports
A NEW KIND of injection moulding
process developed at Warwick University
could mean electronic circuits being
embedded directly within car bumpers
and roofs.
The technology, called IN-SPIRE,
could allow a bumper to act as a
reversing sensor. It also has the potential
to turn roofs into photovoltaic cells to
charge car batteries.
Developed by the Warwick
Manufacturing Group in collaboration
with German injection moulding
equipment manufacturer Battenfeld, the
team originally designed the technique
for painting plastic car parts inside the
injection moulding process.
‘We were looking at ways of avoiding
the paint shop,’ said the project’s
principal researcher Gordon Smith.
‘The coating of a vehicle is said to be
20 per cent of its overall cost. This
fact, combined with the demand for
environmentally-friendly processes,
encouraged us to look at ways to improve
the coatings and the techniques used to
apply them.’
The process produces a thermoset
coating on a thermoplastic moulding
within a single injection cycle.
The properties of the surface are
similar to those that would be
produced by conventional thermoset
painting processes.
The patented technique begins when a
powder coat is explosively sprayed into
the mould cavity using a pressurised
powder feed unit. By this gas blast, the
powder evenly and randomly coats the
cavity walls. The plastic substrate is then
injected using traditional injection
moulding, equipment, tooling and
processes.
A heated tool softens the thermoset
material and forms a film on the tool’s
surface. The heat of the injected
thermoplastic substrate cures the
thermoset material before cooling. The
cycle time depends on the cure reaction
of the thermoset coating material, the
After car bumpers
and roofs, the
technology could
be used for many
other applications
outside the
automotive
industry
FutuRe
of automotive technology
whole process adding only a couple of
seconds to typical injection moulding.
After seeing the success of this
technique the researchers realised they
could add layers into the process. First
they tried it with multiple thin coats of
paint — clear, colour and metallic.
‘Following on from that, we realised
we could build up different
conductivity,’ said Smith. ‘We could
have a semiconducting film, an
insulating paint and then a conductive
paint on top so that we could build up
function on the surface.’
The researchers demonstrated that
polar particles such as pigment
components can be manipulated and
manoeuvred during the injection
moulding process with techniques such
as dye diffusion, which is commonly
used in photo lab printers. In that
application, colour dies are heated so
they vaporise and permeate glossy
paper before returning to solid form.
The result is unpixelated photographs.
Warwick’s team is using a similar
technique to develop areas of conduc-
tive pathways on an injection-moulded
part. ‘If the injection moulding
the EnGIneeR 21 APRIL–4 MAY 2008 35
machine is charged with different
materials, you can develop individual
circuits depending on which injection
gun you fire,’ said Smith.
Researchers are still deliberating on
how to produce the exact design
required for the electronic circuitry.
The next challenge will be deciding
how to commercialise a technology
with such a wealth of possibilities.
Smith said the technology could go
beyond the automotive industry. He
envisages plastic drink bottles with
moving displays created as an integral
part of the bottle. It could also replace
RFID tags hidden inside products for
tracking. The whole plastic product
could effectively be turned into a giant,
impossible-to-remove-tag.
The process will, according to its
developers, be ready for use in
production cars within six months.
Smith has been researching the
technology for 20 years and, while it
seems like it might be coming to
commercial fruition, he does not plan
on an early retirement.
‘An academic is always looking for
the next challenge,’ he said.
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