Chainflex® lasts or your money back!

The tricks and ingenious features of Chainflex® and why we feel so confident about its design

Chainflex® continuous-flex cables deliver longer life and better performance and are ideal for demanding applications on all types of automated machinery. Chainflex® cables are tested over millions of cycles in all types of conditions to ensure optimal performance and can handle tight bending radii in dynamic applications. The range includes control, data, bus, position feedback, fiber optic, coax, servo, power and robot cables. igus® also offers custom cables, as well as pre-harnessed cables for drive technology.

The Chainflex® range was developed by igus® in the 1980s. An increase in the demands of automation technology meant guided cables often failed, despite the cable carrier protecting them continuing to function perfectly. In extreme cases, failures caused by "corkscrews" and core ruptures brought entire production lines to a halt and resulted in high costs. In order to find a solution to this unsatisfactory situation for its customers, igus® decided to take the initiative and create unique cable-design principles to help prevent machine downtimes in factories throughout the world.

igus® was the first company worldwide to develop complete cable carrier systems. Chainflex® continuous-flex cables and Energy Chain® cable carriers are offered from a single source with a complete system guarantee (depending on the application). Fully pre-harnessed ReadyChain® systems are also available.

Picture 1: So-called "cable carrier-suitable" cable - stranded in layers

Picture 2: Conductor and core structures of a Chainflex® continuous-flex cable

Picture 3: Chainflex® continuous-flex cable - stranding in bundles around center cord

Fleece

Cores stranded in layers

Extruded, non-tensionproof center element

Single-wire bundles with short pitch lengths

Center element for high tensile stress

Highly wear-resistant, gusset-filling extruded jacket

Shielding with optimized braiding angle

Gusset-filled extruded inner jacket

Center element for high tensile stress

How can "corkscrews" be prevented?

Picture 4: Shielded "cable carrier-suitable" control cable after only 400,000 with a bending factor of 10 x d

"Corkscrews" refers to the permanent deformation of guided, moved cables caused by excessive stressing. The end result is usually core ruptures, cable failure and machine downtime. How does this happen and how can corkscrews be prevented? One important way is a properly constructed cable. A clear distinction can be made between cables stranded in bundles and cables stranded in layers, for example.

Properties of stranding in layers

Stranding in layers is significantly easier to produce and is therefore offered on the market as so-called "cable carrier-suitable" cables at low cost. However, what appears to be tempting at first glance can quickly turn into an expensive mistake when a corkscrew immobilizes the system being operated with these cables.

How do these problems arise? Looking at the cable structure can be helpful (see picture 1). When stranding in layers, cable cores are stranded in relatively long lengths in several layers around a center cord and then provided with a jacket extruded to form a tube. With shielded cables, the cores are wrapped up with fleece or foils. But what, for example, happens to a 12-core cable constructed like this during normal operation? The bending process compresses the inner radius of the cable and stretches the core in the outer radius. Initially, this works quite well, because the elasticity of the material is still sufficient. However, very soon material fatigue causes permanent deformations. The cores are diverted from their specified paths and make their own compressing and stretching zones. This creates the corkscrew effect, usually followed fairly quickly by core ruptures and cable failure.

Stranding in bundles - tried and tested millions of times since 1989

Stranding in bundles eliminates these problems by means of its sophisticated, multiply stranded internal structure. The litz wires are stranded with a special pitch length first and then the resulting cores are stranded into single core bundles. For large cross sections, they are bundled around a strain relief element. The next step is the renewed stranding of this core bundle around a tension-proof center.

Due to this multiple stranding, all cores change the inner radius and the outer radius of the bent cable several times at identically spaced distances. Pulling and compressing forces balance one another around the highly-tensile center cord giving the stranded structure its inner stability. The stranding remains stable even under maximum bending stress.

What are EMC problems and shield wire breakage?

In principle, cable shields must fulfil two tasks:

Protect the cables from external interferences

Shield any interferences before transmitting them to the outside

Both tasks are equally important because faulty signals can cause considerable damage to a system, as well as to any external systems. This is especially problematic since incorrect shielding usually can not be detected from the outside, which makes trouble-shooting extremely difficult.

How can these kinds of problems arise in the first place? Once again, the answer is to be found in the internal structure of the cable itself: is the shielding designed for the movements of the cable? Although it may be very easy to shield a static cable, it is much more difficult to guarantee the permanent shielding of a moving cable.

With so-called "cable carrier-suitable" cables, the stranding bond of an intermediate layer is wrapped up with foils or fleeces. This stranding bond is supposed to guarantee the separation between the cores and the shield braid. However, something that functions perfectly well for static cables is usually insufficient for continuously bending cables. This is because the foils and fleeces do not create a bond between the stranding, shield and jacket, and may fall apart under stress. Consequently, the metallic shield then rubs on the insulation of the cores causing short circuits. The production of the shield itself is very time-consuming and cost-intensive, hence why it is often used for open braid shields or even simple wire wrappings. The disadvantages are obvious: open shields only possess a limited shielding effect in their moved state – motion and expansion reduce this effect even further. The type of shield is therefore an important point that is not even mentioned in some catalogs.

In the Chainflex® range's approx. 70% linearly and approx. 90% optically covered cables, igus® eliminates these issues by implementing an optimized internal structure. In virtually all shielded Chainflex® cables, a gusset-filled extruded inner jacket over the stranded structure is used. This "second jacket" fulfils two tasks:

It holds the stranded structure together and guides the individual cores.

It serves as a firm, round base for a very tight-fitting shield.

Jacket breakage at (36 x 0.142) after only 900,000 cycles with a bending factor of 7.8 x d

Shield wire breakage – and how this can be prevented

Even during the production of a shield, there are proper procedures that should be followed. Here, an important parameter is the braiding angle.

In the case of "cable carrier-suitable" cables, a tensile load of the shield wires in the outer radius of the cable must usually be taken into account. If an unfavorable braiding angle is to be added, the tensile load increases even further and shield wire breakage is the result.

The consequences range from reduced shielding effects right up to short circuits whenever the sharp wire ends penetrate through the fleeces or foils into the cores. Here, a useful tip: if, after the insulation has been stripped off, the shield can be easily pushed back over the jacket, the shield is then usually unsuitable for use in moved continuous-flex applications. This is a problem that igus® has now solved with a direct approach:

The shield braiding angle determined in long-term tests efficiently neutralizes tensile forces and is therefore highly suitable for cable carriers.

Due to the stable inner jacket, the shield can not move where it is not supposed to.

The shield itself protects the stranded structure from torsional forces.

Jacket wear and breakage

Whereas defects in the internal structure are hardly detectable from the outside, jacket problems are immediately visible. The jacket is the first protection for the complicated internal structure. This is why broken, worn and swollen jackets are a serious quality defect. To prevent this problem, as an igus® customer, you can select among 7 jacket materials to adapt your continuous-flex cables to suit the conditions of the environment in which they will operate.

Gusset-filled extruded jacket

With the cable jacket, the production process is an important factor, in addition to the material used. With so-called "cable carrier-suitable" cables, the jackets are usually produced extruded to form a tube and therefore do not provide the necessary support for constant bending.

igus® is the first manufacturer of cable carrier systems to offer the so-called "gusset-filling extruded" jacket.
The involves jacket material being injected between the core stranding and powdered with talc, ensuring the stranded structure does not open up. It also makes sure the cores are guided properly. The special characteristic of this type of production is that the intermediate spaces created between the cores during the stranding process are completely filled with jacket material by the high extrusion pressure. As a result, the jacket material creates a channel-like guide which allows the cores to carry out a defined longitudinal movement. The jacket also provides a supportive function.