It's very important for cables used in continuous-flex applications to follow certain construction and performance guidelines in order to prevent cable failure.
Cable failure is one of the leading causes of downtime which is costly for a multitude of reasons as it's a waste of resources, time, and effort to replace, which can result in a considerable loss or production and therefore revenue.
In order to choose the most appropriate cable you would first look for a cable that meets your application requirements and specifications. Application requirements can include things like bend radius, temperature range, oil resistance, jacket material, cable structure, electrical information, and certifications and approvals.
However, it's also very helpful to understand the most typical reasons why cable failure occurs. This can help you prevent making the same mistake when selecting the right cable and installing it correctly in your own application.
Below we've compiled the 6 most common types of cable failure design that engineers should be on the lookout for.
1) Loss of continuity
Copper conductors can sever and break, which causes a loss of continuity when insulated conductors are twisted with an incorrect pitch length or pitch direction.
The cable core then cannot absorb the mechanical load while flexing, so it transfers the force to the copper conductors, which causes them to break under the increased tensile load.
2) Insulation damage
Insulation damage occurs when the insulation integrity of the conductors is compromised. This is caused by material fatigue under constant bending stress, abrasion within the cable structure, and/or conductor strand breakage. All of which can perforate the insulation.
This failure is easily recognizable by the mechanical deformation of the entire cable. The corkscrew or "pigtail" effect occurs when torsional forces are released during operation due to incorrect cable configuration, pitch length and pitch direction. Cables that are constructed in layers rather than bundled are more susceptible to corkscrewing.
4) Jacket abrasion
Jacket abrasion occurs when the outer jacket of a cable wears through to the underlying layer of conductors or shielding. This failure is especially common when using cables with soft jackets. However, this problem can also be caused by a thin wall-thickness that can develop during the jacket extrusion process.
5) Jacket swelling/cracking
The outer jacket of a cable swells when it has been exposed to oils or chemicals it was not designed to withstand. Jacket cracking occurs when the jacket breaks and deteriorates down to the cable's shield, normally as a result of excessively high or low temperatures.
6) Shielding losses/EMC problems
Increased electromagnetic interference (EMI) occurs when the shield, which is designed to protect cable signals from electromagnetic fields, breaks and abrasions due to continuous bending.
Understanding these 6 cable failure modes is essential in order to minimize unexpected production downtime. Recognizing them at the beginning of the buying process increases the likelihood that you will purchase the most optimal cable for your automated application. This will ultimately ensure that you will get the most efficient production possible, which will save you money and time in the long-run.