Stranding: the process of stranding a number of small diameter monofilaments into a large cross-section conductive core according to certain rules.
1. There are two kinds of stranding: normal stranding and irregular stranding.
Normal stranding can be divided into normal concentric single strand stranding and normal concentric strand stranding.
(1) ordinary stranded wire: single wires of the same diameter are twisted regularly layer by layer according to concentric circles, and the direction of each layer is opposite.
(2) combined strand: it is made of single wires of the same diameter and different materials or of different diameters and materials（ Representative products (such as overhead conductors).
Normal concentric strand stranding: it is a kind of stranded wire that is concentric stranded by multiple strands of common stranded wire or bundle wire.
Irregular stranding (strand): a strand formed by multiple single strands in the same direction and not in accordance with the stranding law. The positions of the single strands are not fixed with each other, and the shape of the strand is difficult to keep round.
2. The biggest difference between bundle wire and common stranded wire is that each single wire of common stranded wire has a fixed position and is regularly twisted layer by layer; There is no fixed position between the monofilaments of the bundle, which is not twisted together according to the law of stranding.
3. The characteristics of irregular stranding (bundle): because each single wire in the bundle is twisted in one direction, the sliding allowance between each single wire is large when bending, and the bending resistance is small, so the bending performance of the bundle is particularly good. For the wire and cable products that need to be soft and often move, the bundle is used as the conductor core.
4. Characteristics of stranded core:
(1) good softness; The bending capacity of the cable can be improved by using the wire core composed of several single wires with smaller diameter, which is convenient for the processing, manufacturing, installation and laying of wires and cables.
(2) good stability; The wire core composed of several single wires twisted according to a certain direction and stranding rules, because the position of each single wire in the stranded wire is in the elongation area at the upper part of the stranded wire and the compression area at the lower part of the stranded wire in turn, the stranded wire will not deform when it is bent.
(3) good reliability; Using single wire as conductor of wire and cable is easy to affect the reliability of conductor core due to the non-uniformity of material or defects produced in stranding. The defects of conductor core formed by multiple single wires are dispersed and will not concentrate on a certain point of conductor, so the reliability of conductor core is much stronger.
(4) high strength; The strength of single stranded core is higher than that of single stranded core.
5. Interpretation of terms:
(1) Pitch: the distance of a single wire moving axially for one week.
(2) Pitch diameter ratio: ratio of the pitch length of the strand to the diameter of the strand.
(3) The relationship between pitch and strand softness: the smaller the pitch, the better the softness of the strand, the worse the flexibility of the larger the pitch.
(4) . stranding coefficient: the ratio of the actual length of single wire expansion to the pitch length in a pitch of the strand.
(5) . strand direction: right (z) left (s direction)
(6) . compression Conductor: the common tight conductor is tight pressed round, fan shaped and pressed tile (five core cable) semi-circular (two core cable)
6. Purpose of tightening:
(1) Tight compression sector Conductor: reduce cable outer diameter and save product cost and reduce cable weight.
(2) Compact compression circular conductor: improve the surface quality of stranded conductor, reduce the diameter of conductor, improve the filling coefficient of conductor, smooth and round conductor surface after tight pressing, and the electric field on the conductor surface is even. Save materials and reduce costs（ Learn more cable technology. Please click here. A lot of dry goods are waiting for you.)
7. Conductor classification:
According to GB/T3956 conductor of cable, there are four kinds of conductors, namely, type 1, type 2, type 5 and type 6. The first is solid conductor and the second is stranded conductor, which is suitable for the conductor of fixed laying cable; The fifth and sixth are stranded conductors, which are used for flexible cables and flexible wires, and the sixth is softer than the fifth.