Unveiling Cable Manufacturing — Basic Process Chapter (Part 2)
The Birth of a Cable (Part 2): Inner and Outer Excellence — How the Sheath Becomes the Cable’s “Armor”?

In our previous article, we explained how conductor insulation achieves precise and complete encapsulation. In this issue, Dongguan Dosing Automation Technology Co., Ltd. (DOSING) will take you further into the production line to explore the final critical process of cable formation — outer sheath extrusion. See how we armor the already-formed core assembly with a robust “shield,” creating a truly tough and durable cable.

I. More Than Just Appearance: The Sheath as the Cable’s “Multi-Functional Armor”

While the insulation layer provides basic electrical protection, the sheath serves as the cable’s “all-around armor” against external challenges. Its role goes far beyond aesthetics:

• Mechanical Protection: Effectively resists wear, impact, and compression during installation and use, ensuring the internal structure remains intact.

• Environmental Resistance: Offers weather resistance, oil resistance, chemical corrosion resistance, UV protection, and moisture waterproofing, ensuring stable performance in complex and harsh industrial or outdoor environments.

• Flame Retardancy: Particularly in applications like construction and rail transit, the sheath must use flame-retardant materials to inhibit fire spread and buy valuable time for safe evacuation.

• Identification: Clearly marks cable type, voltage, manufacturer, and other information through colors and printing, facilitating easy identification and maintenance.

II. Tailored Protection: How to Choose the Right “Armor” Material for the Cable?

Different application scenarios require sheath materials with specific properties. Our outer sheath extrusion production line excels in handling various materials:

• PVC (Polyvinyl Chloride): An economical all-purpose sheath with good flexibility, corrosion resistance, and flame retardancy. Widely used in indoor wiring, appliance cords, etc.

• PE (Polyethylene): An excellent outdoor sheath material with superior insulation properties, low-temperature resistance, and moisture resistance. Suitable for communication cables, overhead outdoor lines, and submarine cables.

• TPE/TPU (Thermoplastic Elastomer/Polyurethane): High-end flexible materials offering extreme elasticity, bend resistance, and tear resistance. Often used in robot cables, drag chains, and medical cables where high flexibility is required.

• LSZH (Low Smoke Zero Halogen): An environmentally friendly and safe sheath that produces low smoke and releases no toxic gases when burned. Ideal for high-density public spaces like subways, airports, hospitals, and high-rise buildings.

III. Process Challenges: Core Difficulties in Crafting the Perfect Armor

Applying an outer sheath to a structurally complex core is not just a technical process but an art. The main challenges include:

• Preventing Compression Deformation: The core structure (especially pair-twisted or shielded wires) is delicate. Improper pay-off tension or poorly designed dies can easily lead to crushing or twisting, severely compromising cable performance.

• Ensuring Uniform Thickness: A sheath that is too thin provides inadequate protection, while one that is too thick increases costs and reduces flexibility. Consistent thickness is key to balancing protection and economy.

IV. DOSING’s Solutions: Forging Indestructible Cable Armor

To address these core issues, Dongguan Dosing Automation (DOSING)’s outer sheath extrusion production line offers a range of professional solutions:

• Support-Type Pay-Off and Precision Tension Control: Using a shaftless support pay-off structure, the cable reel is gently “lifted” rather than “clamped,” enabling near-zero tension, twist-free pay-off to prevent core deformation from the source.

• Optimized Die Head and Centering Guide System: Our specially designed die head with precision internal core guidance ensures the core remains centered. The molten sheath material evenly envelops the core from all sides, forming a stable “circular waterfall” effect that avoids eccentricity and uneven pressure, protecting the core from deformation.

• High-Precision Extrusion and Closed-Loop Control:

  • Customized Screw and Barrel: Designed for different sheath materials (e.g., high-viscosity PE or soft TPU) to ensure stable, pulse-free output — the foundation of uniform thickness.

  • Servo Drive System: High-precision servo motors synchronize extrusion and traction with millisecond-level response, eliminating thickness variations caused by speed fluctuations.

  • Optional Online Diameter Gauge: For high-demand applications, a laser diameter gauge can be integrated for real-time monitoring and closed-loop adjustment of the sheath outer diameter. Any micron-level deviation is instantly corrected, ensuring perfect thickness uniformity.