Reliable cables for energy chain systems from Treotham

Treotham
provides a large range of high quality igus chainflex cables that can be used
in energy chains for various applications.

Due to the
increase in automation and industrial production, the use of energy chains is rapidly
growing. The requirements for cables that supply machine parts with media, data
and energy are also rising as factors such as speed and acceleration become
more demanding.

Movement in
the energy chain spans from horizontal or vertical for simple applications, now
to multiple, complex rotations for six-axis robot applications. The system is
sometimes referred to as the umbilical cord of a machine, as both the cable and
the chain must perform every precise movement. Therefore the reliability and
service life of moving cables could be the most important factor of the whole
system.

It is also extremely
important that the design and material of the cables are adapted to the energy
chains so that they can withstand the mechanical loads from millions of cycles
without failing and succumbing to the corkscrew effect.

Cables that
are used in moving applications, especially energy chains, are subject to
increased strain. Standard tests that determine the durability of the cables
often neglect to take field experience into account. Field experience shows
that even highly flexible cables often reach their load limits while moving in
energy chains. Therefore it is evident that in conventional standard tests such
as those carried out by VDE, IEC or UL, the service life cannot be predicted.

There are some
well recognized test procedures from various institutes in the cable industry,
however the procedures are very basic and do not include specific requirements
for continuous movement in the energy chain.

The bending
fatigue test as per VDE and standard wear test don’t satisfy requirements of a
chain-cable combination. In the bending fatigue test the cable has a completely
different movement sequence then the movement of the cable in an energy chain.
Many cable designs that meet these requirements quickly fail tests conducted
under real world conditions.

Standard wear
tests, which use needles, sand paper or razor blades to determine the wear of a
material, can only be used to make a general comparison. This test is not good
when determining the durability of a jacket material in an energy chain. It is
important to test the wear of the material by testing the chain and cable
material together so that they can adapt to one another.

Igus
thoroughly tests the jacket materials of cables by rubbing them against chain
materials to determine the degree of wear. As a result they use materials such
as PVC, PUR and TPE which offer minimal wear compared to standard PVC cables
and provide optimal performance when used in an energy chain.

The design of
cables for moving applications has also changed drastically over time, which
has led to cables being braided in bundles. In a complex process, wires are
braided in single bundles consisting of three, four or five wires, which are
then braided with each other. For large cable designs, this is done around a
strain-relief element. The result is a cable that is built for movement and
ideal for use in chains. Unlike a cable with layered braiding, each of the
wires in the energy chain is moved an equal amount at both the inner and outer
radii. This helps prevent stretching and buckling on one side.

For more extreme movements, cables with more
complex designs are used. One of the applications with the most extreme
movements of bending and twisting, are industrial robots. They use damping
elements to give the wires in robot cables the essential freedom of movement
within the cable. The tighter the cable is wound and the closer the cable gets
to its breaking point, the more difficult it becomes to twist. Special shields
and outer materials also ensure optimal cable durability.

It is also
important to consider environmental factors when selecting the right energy
chain and cable. Depending on the application, they may be exposed to
chemicals, dirt, dust, moisture, impacts or extreme temperatures at times when
they are used in harsh industrial conditions. Under these conditions, field
experience is extremely important for testing the resilience and service life
of the cables. For this reason, igus operates a 1750 square meter test lab in
which applications are run around the clock on 58 different test systems. This
results in over two billion test strokes per year.

In one
application, a sea container was specially modified to generate temperatures of
-40¡C to 60¡C and to test high temperature fluctuations. Energy chains and
cables were moved millions of times in the container and the results were
evaluated accordingly. This is completely different from the usual cold bending
test, where a cable is wrapped once around a mandrel, cooled down to the
temperature to be tested and then moved once. If the exterior mandrel shows no
signs of visible damage, then the cable is considered “safe” for the
respective temperature.

Therefore, the
reliability of a moving cable depends on a large range of factors whose effects
can ultimately only be tested and proven under real-world conditions.














Cross-sectional
look at braiding in bundles: As with steel cable designs, all of the wires are
put under the same amount of stress here.

Special
damping elements grant the wires in robot cables the necessary freedom of
movement within the cable. This guarantees a service life of 5 million cycles.

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