The main parameters of the stranding process are: stranding pitch, stranding coefficient and stranding direction
1. Hinge pitch
1. What is the distance (h) that a single strand rotates along the strand axis for one week is called the stranding pitch. The ratio of pitch to diameter is called the pitch to diameter ratio or pitch multiple.
Taking regular concentric stranding as an example, there is a relationship between the pitch of the stranded wire, the outside diameter and the length of a single line within a pitch as shown in the figure.
As shown in the figure, the formula for calculating strand pitch is as follows:
H = LSin alpha = PI D ´ tg alpha
L=
In the formula: h: twisted wire pitch length;
L: the spread length of a single line within one pitch;
D´ : outer diameter of pitch circle, D´= d-d;
D: Outer diameter of stranded wire;
d: single wire outside diameter;
α : helix lift Angle. 2. Measurement of hinge pitch
Measuring tools: vernier caliper, steel ruler, tape measure.
Measuring method: direct measuring method, untwisting method, scratch method.
3. Hinge pitch diameter ratio
Pitch to diameter ratio is the ratio of the length of the pitch to the outside diameter of the stranded wire, called the practical pitch to diameter ratio
m =
It is expressed by the pitch of the strand and the pitch circle diameter of the strand, that is, the ratio of the pitch to the pitch of the strand, called the theoretical pitch diameter ratio
m´ = =
Two, stranding coefficient Jia Feng copper industry
The stranding coefficient refers to the ratio of the actual length of a single wire to the length of the stranding wire pitch within a stranding pitch. The calculation formula is:
K =
Where K is the stranding coefficient;
L: the length of the single line of each pitch length in the twisted wire after it is expanded straight;
h: length of twisted wire pitch.
The relationship between the actual length of a single wire in the strand and the length of the strand is also expressed by the stranding rate. Stranding rate refers to the ratio of the difference between the actual length of a single wire and the length of the strand pitch to the length of the strand pitch within a pitch. The calculation formula is:
λ = ×100%
Where λ : stranding rate;
L: single line development length;
h: length of twisted wire pitch.
Third, the direction of the twisted concentrically twisted each layer of the twisted direction of the opposite, the reason is that the multi-layer of the twisted line are twisted synthetic round when the twisted line is subjected to tension, the rotation torque generated by each layer cancels each other, to prevent the layer of single line to rotate in one direction and loose, but also to make the twisted line to produce a torque component, to avoid the twisted line in the untensioning phenomenon.
The stranding direction is divided into left and right, for the stranding direction, the producer must pay attention to, the product standard strictly stipulates the stranding direction of the outermost layer of the stranded wire, the power cable copper stranding standard stipulates that the outermost stranding direction is left, and the adjacent layer is twisted to the opposite.
Method of judging the direction of stranding:
1. S to (left) Z to (right);
2. Left Hand (or right hand) rule