Example 1: tested, tested, tested! Servo cable structure

Here, the servo cables are highly flexible motor connection cables with a complete copper shield and an integrated, shielded pair of control cores. This cable type was selected due to the fact that here the problematic case of an outof- round braid form due to the different core cross sections is a significant factor and that the various bending behaviors of the production methods are therefore emphasized.

Both cables are provided with identical nominal cross sections and insulation materials. Cable A is equipped with an internal jacket and cable B with a fleece taping and fillers.
The experimental production (sample B) already shows the formation of a corkscrew after 145,000 double strokes. In the case of a cable, the so-called corkscrew refers to a wave-shaped deformation like the one that can be seen in the following picture on sample B.
Whereas, in the case of cable A, the internal jacket fills up the gussets and a round braid structure is created as a result, cable B requires fillers in the gussets. Like the core, the fillers also consist of filbrated polyethylene. They are easy to compress and are therefore hardly capable of taking over any supporting effects. Whereas the internal jacket, which is made of TPE, and the cable A center, which consists of cordage, hold the cores in a defined position, the cores of cable B are able to move about uncontrolled. During the bending process, a core has detached itself from the composite braid structure and has been shifted in the inner bending radius with respect to the center and on the outer bending radius with respect to the jacket. This results in corkscrew-type deformations that repeat themselves periodically with the pitch length.