What are the limits to bend radius’ on chainflex® cables?

When using cables, no matter what the type, it is important that the minimum bend radius is considered and adhered to. But if you are new to the world of cables, you may need to go back to basics by asking what is a bend radius before you look at the limitations.

What is a bend radius?

image of a bend radius

What is a bend radius? The bend radius is the radius at which a cable can be bent without damaging its integrity or function. When considering this we take the exact centre of the cable, i.e. the neutral fibre. Basic explanation is the smaller this radius, the more durable the material must be. Compare it to the human body and the spine. The smaller I want to distrort my body, the more flexible my spine has to be. If the flexibility is not there (which it is not) then the more likely I am to break my spine.

For our e-chain® systems, the same principle applies, however the minimum bend radius must be greater than that of the cable so that the cable used is safely maintained. Energy chain manufacturers offer different bend radiuses to allow customers to correctly match them to their cables and igus® is no exception. We offer a large range of energy chains with different bend radius’ to suit the varied range of customer applications.

The bend radius of the e-chain® should be greater than the largest radius requirements of the cables inside – this can be obtained by multiplying (bending factor x overall diameter (OD)).

This compliance ensures long cable lifetime and ultimately, application lifetime: too tight a bend radius and the cable elements will fatigue quickly. The larger the radius, less stress will be exerted on the cables – in turn producing a longer service life.

Moreover, operators must note the advised temperature range of the cable in order to not allow the cable to become hotter than is safe, since the materials might break down. Similarly, cold temperatures can make the cable materials stiff and brittle, reducing the life.

What is the correct bend radius for a cable?

An important factor to ensure a long service life for a cable is the bend radius.
We can distinguish these between 3 different specifications when referring to the bend radius of our chainflex® cables:

  • Fixed: The cable is brought into this radius just once for installation and then it no longer moves. This is described in the DIN.
  • Flexible: This is the bend radius that the cable occasionally adopts when moving freely. Here, the number of bends is not defined. There are also standardised tests in the norm.
  • Chain: This is the radius of the energy chain specified when it is in continuous movement. It is not definitive. That is why we at igus always test on real applications.

chainflex® guarantee 

At igus®, all of our chainflex® cables are tested in the 3,800m² test laboratory, located at our headquarters in Germany, to ensure the figures that we release allow customers to find the safest, most long-lasting cables for their applications.

The tests on our chainflex® cables have been carried out for over 25 years and continue to do so over a wide variety of specific strokes and test regimes.

Thanks to this testing and expertise, the flexing lifetime of our cables can be guaranteed for up to 36 months; even in harsh and unusual environments.

The 7 commandments

The resilient designs of our cables can be summarised by the seven basic rules we proudly abide by:

  1. Strain-relieving centre: protect the braiding structure for reliable and safe cores.
  2. Optimised conductor design: optimal strand diameter, pitch length and direction for safe bending.
  3. Core insulation: non-adhering but supportive insulation materials.
  4. Core structure: braided or layered structure to ensure optimised short pitch length.
  5. Inner jacket: extruded inner jacket, rather than woven fabric or filler, ensures no fragmentation.
  6. Shielding: tightly braided structures ensure high EMC and torsion protection.
  7. Outer jacket: jackets made of PVC, PUR or TPE meet myriad specifications, such as UV resistance, low-temperature flexibility, oil resistance – and, ultimately, cost-effectiveness. 

Everything has limits and ensuring you understand the limits is essential to get the best out of the application. This applies to loads, speeds and of course, bend radius where needed. To read more blogs on our chainflex® cables visit https://blog.igus.co.uk/category/chainflex-cables/

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