Talking about the cable production process: stranding of conductors

Stranding (stranded wire): The process of twisting multiple monofilaments with smaller diameters into conductive cores with larger cross-sections according to certain rules.

1. Stranded wire is divided into two types: regular twisting and irregular twisting.

        Regular twisting can be divided into regular concentric single-wire twisting and regular concentric single-strand twisting Regular concentric single-strand twisting:

        (1) Ordinary stranded wire: Use the single wire of the same diameter, in the way of concentric circles, regularly stranded layer by layer, and the twist direction of each layer is opposite.

        (2) Combination stranded wire: It is made of single wires of the same diameter and different materials or different diameters and different materials. (representing products such as overhead conductors)

        Regular concentric strand stranding: It is a strand that is concentrically stranded by multiple ordinary strands or bundles.

        Irregular stranding (bundle wire): a stranded wire formed by twisting multiple single wires in the same twisting direction and not according to the twisting law. all.

2. The biggest difference between the bundled wire and the ordinary stranded wire is that each monofilament of the ordinary stranded wire has a fixed position and is regularly twisted layer by layer; there is no fixed position between the monofilaments of the bundled wire It is not twisted together according to the twisting law.

3. The characteristics of irregular stranding (bundle wire): because each single wire in the bundle wire is twisted in one direction, the sliding margin between the single wires is large when bending, and the bending resistance is small, so the bending performance of the wire harness is It is particularly good, for wire and cable products that need to be soft and often move, the bundled wire is used as the conductive core.

4. Features of stranded wire core:

(1) Good flexibility; the use of multiple small-diameter monofilaments twisted into a core can improve the bending ability of the cable and facilitate the processing, manufacturing, installation and laying of wires and cables.

(2) Good stability; a core of multiple monofilaments twisted in a certain direction and twisting rules, because the position of each monofilament in the strand is alternately located in the elongation area of the upper part of the strand and the lower part of the strand. Compression zone, which does not deform when the strand is bent.

 (3) Good reliability; using a single wire as the conductor of a wire and cable is easily affected by the inhomogeneity of the material or the defects in the twisting process, which affects the reliability of the conductive core. In order to disperse, it will not be concentrated on a certain point of the conductor, and the reliability of the conductive wire core is much stronger.

 ⑷ High strength; compared with a single wire with the same cross-sectional size and multiple stranded cores, the strength of the stranded core is higher than that of the single wire.

5. Terminology Explanation:

 (1) Pitch: the distance that the monofilament advances one week in the axial direction.

 (2) Pitch diameter ratio: the ratio of the pitch length of the strand to the diameter of the strand.

 (3) The relationship between the pitch and the softness of the stranded wire: the smaller the pitch, the better the softness of the stranded wire, on the contrary, the larger the pitch, the worse the softness of the stranded wire.

 (4) Stranding coefficient: in a pitch of the strand, the ratio of the actual length of the monofilament to the pitch length.

  (5) The twisting direction of the twisted wire: right direction (Z direction) left direction (S direction)

 (6) Compression conductor: common compression conductors include compression circle, sector and compression tile (five-core cable) semicircle (two-core cable)

6. The purpose of pressing:

 (1) Squeeze the fan-shaped conductor: reduce the outer diameter of the cable, save the cost of the product and reduce the weight of the cable.

 (2) Press the round conductor: Improve the surface quality of the stranded conductor, reduce the diameter of the conductor, and improve the filling factor of the conductor. The surface of the conductor after compaction is smooth and round without burrs, and the electric field on the conductor surface is uniform. Save materials and reduce costs.

7. Conductor classification:

According to the GB/T3956 "Cable Conductor" standard, there are four types of conductors, namely the first, the second, the fifth and the sixth. The first type is a solid conductor, the second type is a stranded conductor, both of which are suitable for the conductors of fixed laying cables; the fifth and sixth types are stranded conductors, which are used for the conductors of flexible cables and cords. The 5th is softer.