JEC COMPOSITES MAGAZINE - Issue #144 - January/February 2022 - 23

Machine tools - Composites meets Metalworking
the load on the bearings (and hence the
life span) in spindle motors machines
without the use of coolant.
Types of applications
Axis beams
On any form of cutting or milling machine,
the horizontal or vertical beams
are important structures for machine
performance. The mass and stiffness can
limit the working area and accuracy of a
machine as well as the acceleration. The
use of composites allows the weight to
be reduced by up to 50% while stiffness
can allow faster acceleration for the same
deflection, important for the positional
accuracy required for cutting to high
tolerance.
CompoTech has continually developed
its process, which allows accurate
placement of fibre and pressing of
square sections to produce beams with
the straightness and accuracy for this
application. The process development
also considers the internal structure
that manages the torsional stiffness as
well as containing the internal inserts
for threading. Linear rails, drives and
other attachments must be designed
into the composite structure with steel
or aluminium placed appropriately for
fastening. Design analysis is also required
to determine the thermal deflection of
these beams as the difference in thermal
expansion between steel rail and composite
body materials can cause bending.
Not only a consideration for temperature
changes during operation but also for the
thermal bending in production of the
part affected by machining.
Laser cutter gantry
The benefits of composite axis structures
can be demonstrated by Eagle Laser
machine manufacturer. One of the first
laser cutting companies to use composite
technology designed with system first
principles using a carbon fibre traverse.
The iNspire laser cutter model positions
the gantry directly between linear motors
at the sides, applying the drive to the
section centre of mass. The lightweight of
the moving parts provides maximum dynamic
motion while increasing stiffness
Corporation (Japan), has worked closely
with Kyoto University's Professor
Matsubara on academic research to comComposite
spindle cover
ensures accurate cutting. Eagle was able
to take advantage of these improvements
to double the peak acceleration, reaching
the top speed quicker and reducing the
cutting time. They recently released
a 30kW laser cutter, claiming that the
damping of the composite material manages
the vibration at high speed.
Key benefits
- The gantry weight is 44%
lighter compared to the steel
option
- Acceleration increased from
3g to 6g with a top speed of
350m/min
- 30% quicker cutting time.
- Stable temperature and
vibration damping
Spindle structures
Costs implicated with the use of carbon
fibre are justified by the performance gain
of the machine. However, when considering
the significant moving mass of the
milling head, spindle motor, tooling, and
tooling adapters, this gain becomes less
prominent. Hence, it is equally important
to take a whole-system approach to
the design, paying attention to the weight
of these parts. Again, CFRP material is a
solution to this. Creating a hybrid structure
of pitch fibre composite with steel at
specific points for bearing surfaces has
shown to reduce weight while adding
other benefits due to damping.
High-speed machining spindle
The low inertial forces lead to faster processing
speeds, both in the manipulation
of the milling head and for the cycle time.
CompoTech, with the help of Fukuda
pare like for like spindle shafts, showing
that the CFRP-steel hybrid spindle accelerates
to its maximum rotation speed
of 18,000 rpm 17% faster than a steel
spindle, owing to its lower inertia.
Damping properties also lead to
increased stability of machining. As
resonance magnitudes peak at levels half
those of equivalent steel spindles due to
damping, this solution ensures twice the
chip thickness limit safely achieved at a
broader range of spindle speeds. This
means stable machining is achievable
while taking twice the amount of material
i.e., faster feed rate.
These factors combine to give more durability
to the spindle and the tool.
Spindle cover
As well as being light weight, composite
cover tubes produced on high-precision
tooling are up to 50% lower in cost to
manufacture than steel. A high-quality
internal surface is required, which is an
expensive machining process for steel;
but when using a composite solution,
this machining is not required. A great
example where a lightweight solution
is also a low-cost one due to simplified
and reduced process steps from the
considered composite and spindle motor
design combined.
Tools and tool holders
For tooling parts, CompoTech has collaborated
closely with special tool producer
Hofmeister. A variety of different tool
types were tested: end mills, face mills,
milling disks and boring tools as well as
tool extenders and tool holders. Each
case has its own set of design challenges
to work through. The composite part is
designed and produced by CompoTech,
using either fibre placed onto a tool blank
or as a separate component which is then
machined with a shape-locking interface.
The final machining and part assembly is
completed by the customer.
Key production benefits of the new
hybrid milling tool:
N°144 January - February 2022 / jec composites magazine
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JEC COMPOSITES MAGAZINE - Issue #144 - January/February 2022

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #144 - January/February 2022
