MATERIALS | CFRPS
design reinforced with foam
cores, designed and manufactured
by CompoTech, a composite
manufacturing specialist
based in Czech Republic,
the company reduced the
weight of the beam by
44% while increasing its
stiffness.
These improvements
enabled Eagle to double
the peak acceleration of the
beam from 3g to 6g, which,
in turn, reduced the time
required to cut a sheet of material
in the machine by up to 30%.
Furthermore, the extra stiffness and
improved damping characteristics
of the part resulted in accuracy
improvements of up to 50%.
The development of composite
transfer beams, meanwhile, was the
aim of press manufacturer Schuler,
which replaced a basic square
section beam with a 3D hybrid
composite version of a steel T-slot
beam. The resulting beam weighed
just a quarter of the original section
while demonstrating an axial modulus
of 400GPa, which increased its
natural frequency of resonance while
decreasing its dynamic response.
This allowed the machine to run at
a faster rate than was previously
possible, from 20 strokes a minute to
32 – increasing its output by 40%, on
average.
“It’s not just in large parts that
the properties of CFRPs can yield
real bene ts,” adds Carter. “A
steel/composite hybrid milling
tool developed by CompoTech,
for instance, can perform faster
and machine more accurately than
conventional alternatives. The tool
also imparts improved surface
roughness meaning that, in certain
circumstances, it can do the job of
two varieties of steel tool, for rough
and nal machining. This increases
milling productivity, decreases
machining time and reduces
machining cost.”
The reduction in weight – up to
40% – and the increased stiffness
enabled by the use of carbon
bres also enhances the damping
properties and increases natural
frequency of the tool – reducing
unwanted vibrations in the
machining process, thus giving
the tool more stability.
The low weight of the
milling tool also means
that less energy by the
machine is used in nonloaded
positioning, while
The reduction in weight – up to 40%
– and the increased
sti ness enabled by the
use of carbon bres also
enhances the damping
properties and increases
natural frequency
its lower inertia slashes
peek energy in acceleration.
This can also reduce wear on
parts of the machine, meaning
that the lifetime of the machine and
the durability of the tool tip can be
increased. If you consider replacing
the spindle motor and the bearings
with composites, these parts can
reduce the lifetime cost of a machine.
In some cases, they can allow a
machine to handle and machine with
a larger tool where weight might be
the restriction.
“Of course, CFRPs are
signi cantly more expensive than
steel or aluminium, which might
be enough to stop some machine
designers from considering the use
of parts made from such composites,”
says Carter.
“To maximise the stiffness of the
nal parts, CompoTech employs
Graphite Carbon bres made from
pitch, rather than the more common
polyacrylonitrile (PAN) bres.
Differences in their microstructures
mean that while they are not as
strong, pitch-derived graphite
carbon bres possess
a Young’s modulus
signi cantly higher
than that of their PAN counterparts,
making them ideal for such stiffnessdriven
applications.”
Furthermore, Carter adds,
modern manufacturing
methods can be employed to
signi cantly narrow the cost
gap between CFRPs and
metals. Automated axial bre
placement allows bres to
be aligned along the length of
the tube or beam, suiting it for
machine members and other
components that must be highly
resistant to bending loads. The
vibration behaviour of the parts
can also be tailored through
this process.
The dimensions and
wall thickness of the part
can be adjusted to tune
its natural frequencies,
for example, and
damping materials, such
as rubber and cork llers,
can be incorporated into
the structure. Additionally,
internal foam reinforcements
can be used to improve the
vibration stability of the walls of
large-section parts.
Finally, the performance bene ts
associated with the use CFRP parts
and tools rather than conventional
metallic alternatives can be
signi cant – helping to offset any
extra expense as well as improving
some lifecycle costs.
“Designers and engineers
in the manufacturing industry
may be shy of specifying CFRPs,
underestimating their bene ts
while overestimating the cost and
complexity associated with their
use,” concludes Carter. “As we have
seen though, the use of composite
components can play signi cant
role in boosting the performance of
machines.” !
of the tool...
CompoTech’s steel/
composite hybrid
milling tool (above)
and spindle (below)
can perform faster
and machine more
accurately than
conventional
alternatives.
36 WWW.EUREKAMAGAZINE.CO.UK | MARCH 2020
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