Published: 2025-08-04 13:38:42
The cabling process of the cable
Stranding is a key step in cable manufacturing, referring to the process of twisting multiple insulated conductors (or ones that include fillers, shielding, and other components) together according to certain rules to form a cable core with specific structures and properties. This process not only affects the mechanical and electrical performance of the cable but also directly relates to the ease of subsequent sheathing processing. The following is a detailed analysis of the cable stranding process:
Preparations before cable formation
Insulated conductor inspection: Strict inspection is conducted on the conductor after insulation extrusion, including insulation thickness, outer diameter deviation, appearance quality (such as whether there are bubbles, scratches, scorching, and other defects), and electrical performance (such as insulation resistance and breakdown voltage), to ensure that the conductor meets process requirements and to prevent unqualified conductors from entering the cable-laying process.
Preparation of filling materials: When there are gaps after multiple wire cores are twisted, filling materials (such as polypropylene rope, asbestos rope, rubber strips, etc.) are prepared. These serve to make the cable core structure rounder and stable, reducing stress concentration during subsequent sheath processing. The filling material must have a certain degree of flexibility and corrosion resistance, and must not affect the overall performance of the cable.
Equipment commissioning: Check key components such as the stranding mold, traction device, and tension control system of the cable forming machine to ensure normal operation. Adjust the rotational speed, traction speed, and tension parameters of the cable forming machine according to cable specifications (such as core count, core diameter, twisting pitch, etc.) to ensure tying quality.
The core steps of cable formation
Setting and tension control: Multiple insulated wire cores are installed separately on the pay-off tray of the cable-forming machine, and the tension controller adjusts the pay-off tension of each core to ensure uniform tension across all wires. Uneven tension can cause uneven force on the wires, which may cause cable core deformation, insulation damage, or even affect the cable's electrical performance.
Twisting arrangement: The wire core enters the cable-forming mold through the guide wheel and is twisted according to preset twisting directions (clockwise or counterclockwise) and pitch. Twisting pitch (the distance the wire core moves forward by rotating around the cable core axis) is a key parameter. Too small a pitch increases cable flexibility but also increases material consumption; Excessive pitch reduces cable flexibility and structural stability. Cables with different core counts have different arrangements. For example: 2-core cables are usually arranged in parallel or twisted together; 3-core and 4-core cables mostly use circular twisting and symmetrical distribution to ensure a neat cable core.
Filling and Tape Wrapping: During the twisting process, filling material is synchronously filled into the cable core gap to make the cable core structure tight. Then, the wrapping tape (such as non-woven fabric, polyester tape, steel tape, aluminum strip, etc.) is wound around the cable core by a wrapping machine. Its functions include: fixing the cable core structure to prevent looseness; enhancing the mechanical strength of the cable core; serving as the base for the shielding layer (such as steel and aluminum strips, which can also serve as shielding); and preventing sheath materials from penetrating the cable core gap. When wrapping, ensure the tape is flat and tight, with even overlap to avoid wrinkles and breakage.
Traction and Take-In: The twisted cable core is conveyed by a traction device to the reel. During reeling, a stable traction speed must be maintained to match the pay-off and winding speeds to avoid additional stretching or twisting of the core cable. The specifications of the reel must match the cable length and diameter to ensure the core is neatly arranged for subsequent processing and transportation.
Key process requirements for cable formation
Structural roundness: The roundness of the cable core directly affects the uniformity of the sheath's thickness. If the cable core is not round, the sheath is easily penetrated at thin points, and thicker parts increase material costs. By reasonably selecting filling materials and twisting parameters, cable core roundness can be ensured.
Tension uniformity: Maintaining consistent tension across all wire cores and filling materials throughout the process is key to preventing cable core deformation and damage. Modern cable forming machines are usually equipped with automatic tension control systems to monitor and adjust tension in real time.
Stranding direction and pitch: Determine the stranding direction based on cable usage requirements. For example, mobile cables typically use alternating left and right multilayer strands to enhance flexibility; Fixed-lay cables can be stranded in a single direction to ensure structural stability. Stranding pitch must be strictly controlled according to cable specifications and standards to ensure compliance with relevant industry standards (such as GB, IEC standards).
Tape quality: The lap width and tension of the strap should be moderate; if it's too loose, the strap may fall off, while if it's too tight, it may compress the cable core. Metal strap wrapping must also ensure conductivity at the joints (for example, the overlap joints of steel straps need to be welded or bonded with conductive adhesive) to guarantee shielding effect.
Inspection after cable formation
After cable formation is completed, the cable core must undergo visual inspection (such as whether it is round, whether the wrapping is flat, if there is exposed wireless core, etc.) and dimensional measurement (such as cable core outer diameter deviation). For important cables, electrical performance tests (such as insulation resistance, partial discharge amount) and mechanical performance tests (such as bending tests) must be conducted to ensure the cable quality meets requirements.
The cable formation process is the core step in forming cable structures, and its quality directly determines the overall performance and service life of the cable. By strictly controlling each process parameter, stable structures and reliable cable cores can be produced, laying a solid foundation for subsequent sheath extrusion and other processes.