Understanding Continuous-Flex Cable Failures: Causes, Symptoms, and Prevention 
Ensure reliable cable performance in demanding applications 

Continuous-flex cables are essential in dynamic applications, such as robotic arms, conveyor systems, and automation equipment. However, improper cable construction, unsuitable materials, or incorrect installation can lead to failures. This guide explores the key symptoms of cable failure, their causes, and practical solutions for prevention.

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1. Loss of Continuity 

Symptom: 
Copper conductors sever and break, resulting in a loss of electrical continuity. 

Causes: 

• • Incorrect pitch length or pitch direction of insulated conductors.
  • Inadequate cable core design that cannot absorb mechanical load during flexing.
  • Excessive tensile stress transferred to copper conductors.

 

Prevention Tips: 

• • Choose cables with optimized pitch lengths and directions tailored for continuous-flex applications.
  • Use cables with reinforced cores designed to absorb mechanical loads effectively.
  • Perform regular inspections to detect early signs of conductor stress.

 

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2. Insulation Damage 

Symptom: 
Compromised insulation integrity leads to short circuits and electrical failures. 

Causes: 

• • Material fatigue under constant bending stress.
  • Abrasion within the cable structure due to friction between conductors and other elements.
  • Perforation caused by conductor strand breakage.

 

Prevention Tips: 

• • Use insulation materials designed for high flexibility and durability.
  • Implement strain-relief mechanisms to reduce stress on the insulation.
  • Avoid excessive bending radii to minimize fatigue.

 

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3. Corkscrew (or "Pigtail") Deformation 

Symptom: 
The cable exhibits mechanical deformation resembling a corkscrew shape. 

Causes: 

• • Release of torsional forces due to incorrect cable configuration.
  • Improper pitch length or pitch direction during construction.
  • Layered cable construction instead of bundled configurations.

 

Prevention Tips: 

• • Opt for cables with proper torsional balancing and pitch optimization.
  • Select cables designed with bundled constructions for better mechanical stability.
  • Perform torsion tests during installation to ensure alignment with operational demands.

 

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4. Jacket Abrasion 

Symptom: 
The outer jacket of the cable wears through, exposing conductors or shielding. 

Causes: 

• • Use of soft jacket materials prone to wear.
  • Thin wall-thickness developed during the jacket extrusion process.

 

Prevention Tips: 

• • Choose cables with abrasion-resistant outer jackets, such as polyurethane or thermoplastic elastomers.
  • Ensure uniform wall-thickness during extrusion processes.
  • Avoid dragging cables over rough surfaces during installation or use.

 

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5. Jacket Swelling / Cracking 

Symptom: 
The outer jacket swells due to chemical exposure or cracks due to extreme temperatures. 

Causes: 

• • Exposure to oils or chemicals incompatible with the jacket material.
  • Excessively high or low operating temperatures.

 

Prevention Tips: 

• • Use cables with chemical-resistant jackets designed for the application environment.
  • Select materials rated for the expected temperature range.
  • Inspect the cable regularly for early signs of swelling or cracking.

 

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6. Shielding Losses / EMC Problems 

Symptom: 
Increased electromagnetic interference (EMI) due to broken or abraded shielding. 

Causes: 

• • Abrasion of shielding layers caused by continuous bending.
  • Fatigue-induced breakage of shield wires.

 

Prevention Tips: 

• • Use cables with robust shielding designs, such as braided or foil shields.
  • Ensure proper installation to minimize unnecessary bending stress.
  • Perform EMI testing to verify shielding integrity.

 

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Conclusion 

Continuous-flex cables are critical in dynamic applications, but improper design or installation can lead to failure. Understanding the symptoms and causes of these failures allows engineers to select the right cables, implement preventive measures, and ensure reliable performance. 

Key Takeaways: 

• • Choose cables specifically designed for continuous-flex applications.
  • Regularly inspect cables for early signs of wear or damage.
  • Follow manufacturer guidelines for installation and maintenance.