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Example 12: tested, life-span comparison of CF21.UL and CF27.D

Long-term test of chainflex® servo cables

Frequent manufacturing tests increase the functional reliability of machines. Besides the continuous tests of new setups, materials and customer requirements in the igus® in-house laboratory, igus® also conducts tests during the production.

Besides batch tests, which immediately reveal manufacturing faults and offer maximum reliability to the user, long-term tests are also frequently carried out. These long-term tests that may take up to four years – and explain the complexity of such systematic series of tests – are necessary if one wants to fulfill the ever-increasing requirements of the market.

This also applies to the long-term test of the chainflex® servo cable families - CF21.UL and CF27.D. These servo cables based on modular design, which differ in their production detail only in their interior and exterior jacket materials, have been tested in the lab for 2.5 years with a radius of 100 mm, a travel of approximately 8 m, an acceleration of about 6 m/s² and a speed of approx 3.5 m/s.

The number of cores/combination of cross sections was selected deliberately, which are very popular in mechanical engineering, but lead to failures in many normal – the so called "chain-fit" – cable assemblies due to the very asymmetrical structure.

CF21.UL CF21.UL: Entire stranding and outer jacket without damage
CF27.D CF27.D: Entire stranding and outer jacket without damage
CF21. No shield wire breaks after more than 10 million bends
CF27. No shield wire breaks after more than 10 million bends
Deliberately incorrect chain filling to simulate a real application.

The specimens, CF21. (4x4 mm² + 2x1.0 mm²) as well as CF27. (4x4 mm² + 2x1.0 mm²), which are continuously electrically monitored during the test phase, have been tested in a real chain assembly in continuous operation.


After more than 10 million individual strokes the cables were taken apart and examined. As can be seen from the detailed photos, no wire breaks could be detected in the single conductors, nor any changes in the insulations. Only slight abrasion marks on the outer jacket that cannot affect the functionality show that the cable has completed a large number of strokes.


The assembly philosophy with gusset-filling, pressure extruded inner jacket and with pressure extruded outer jacket, clearly shows its long service life and clear advantages compared to the commonly used cables mostly assembled with fillers and tapes.

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More information on Chainflex® cables


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