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

The purpose of this test is to determine the advantages of the more expensive internal jacket in shielded servo cables versus the less expensive fleece taping with fillers. With flexible shielded cables, the shield is usually separated from the composite core structure. On the one hand, this is done in order to achieve a rounder braid and, on the other, friction between the core insulation sheath and the braided shield structure is prevented due to the separation of the cores and shield. This can be achieved with an internal jacket or a fleece taping which is wrapped around the composite core structure. The internal jacket is more sophisticated and is therefore more expensive to produce. Following the twisting process, the composite core structure must run through the extruder in which the internal jacket is then put on. In contrast to this method, the fleece tape can be put on between the twisting point and the reeling-up device during the twisting process and therefore does not require a separate process.

Sample B with fleece and filler experimental production 4x10+(2x1.0) C

Sample A with internal jacket igus® Chainflex® CF27.100.10.02.01.D

Comparison between the igus® solution with the gusset-filled internal jacket and the fleece version with fillers

Here, the servo cables are highly flexible motor connection cables with copper shields and integrated, shielded pairs of control cores. This cable type was selected because the different core cross sections can be problematic if the cable has not been produced properly.

Sample A: CF27.100.10.02.01.D (4x0.39 inches2 + (2x0.039 inches2) from igus®

Sample B: experimental (4x0.39 inches2 + (2x0.039 inches2)

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 test production (sample B) already shows the formation of a corkscrew after 145,000 cycles. A cable corkscrew refers to a wave-shaped deformation like the one in the picture (right - see sample B).

In cable Sample A, the internal jacket fills up the gussets and a round braid structure is created as a result (cable B requires fillers). Like the core, the fillers are made from filbrated polyethylene. They are easy to compress and have no real supportive effect. Whereas the internal jacket, made from TPE, and cable A's center cord hold the cores in a defined position, while the cores of cable B are able to move about uncontrolled. During the bending process, a core detached itself from the composite braid structure and shifted the inner and outer bending radii jackets towards the center resulting in corkscrew deformations.

cable cycles

Assessment

Despite the extremely low bending factor of 4.76, no signs of wear can be detected in sample A (CF27.100.10.02.01.D) even after 5 million cycles. Sample B, on the other hand, with its fillers and fleece taping succumbs to a corkscrew formation after just 145,000 cycles. The result justifies spending more on a cable with a gusset-filled internal jacket.