Cores wound in layers

Stranding: Structure of cables for energy chains

Stranding, also known as twisting, refers to the winding of cores in multi-core cables around a core element in order to reduce the mutual interference between the electrical conductors. Stranding plays a decisive role in the design of cables for movement. In principle, a distinction can be made between cores wound in bundles and cores wound in layers.

What is meant by cores wound in layers?
The cable cores are wound more or less tightly and usually relatively long in several layers around a centre and provided with a jacket extruded onto a hose. In the case of shielded cables, the core is also wrapped with non-woven material or films.

Cores wound in layers are much easier to manufacture than cores wound in bundles and are therefore available on the market in so-called "chain-compatible" cables at low cost. However, what is tempting at first glance can quickly turn out to be an expensive mistake in everyday use with more than 7 cores.

The bending process compresses the core in the inner radius of the cable during the movement and stretches the core in the outer radius. This usually works well at the beginning because the material flexibility is still sufficient. However, material fatigue soon causes permanent deformation and the cores create their "own compression and stretching zones" by deflecting from the predetermined path: A corkscrew develops and core rupture usually follows quickly afterwards.

For 7 cores or more cores wound in bundles are recommended.