Do you know how cables and wires are made?
The basic unit of measurement is the length of wires and cables. All wires and cables are made by adding insulation, shielding, cabling and protective layer on the outer layer of the conductor from the beginning of conductor processing. The more complex the product structure, the more layers it will stack.
1.drawing of copper and aluminum single wire
Under normal temperature, the common copper and aluminum pole materials of wires and cables can pass through the die holes of one or several drawing dies by wire drawing machine, so as to reduce the cross section, increase the length and increase the strength. Wire drawing is the first process of wire and cable companies. The main process parameter of wire drawing is die matching technology.
2 single wire annealing
When the copper and aluminum single wires are heated to a certain temperature, the toughness of the single wires can be improved and the strength of the single wires can be reduced by recrystallization, so as to meet the requirements of wires and cables for conductor cores. The key of annealing process is to stop the oxidation of copper wire.
3. Conductor stranding
In order to improve the softness of wires and cables and facilitate the laying and installation, the conductive core is made of multiple single wires. From the form of conductor core stranding, it can be divided into regular stranding and irregular stranding. Irregular stranding can be divided into bundle stranding, concentric compound stranding, special stranding, etc.
In order to reduce the occupied area of the conductor and the geometric size of the cable, the compact form is adopted while the conductor is twisted, so that the ordinary circle is changed into semicircle, fan-shaped, tile shaped and compact circle. This kind of conductor is mainly used in power cable.
Plastic wires and cables mainly adopt extruded solid insulation layer. The main technical requirements of plastic insulation extrusion are as follows:
4.1. Eccentricity: the deviation value of extruded insulation thickness is an important mark reflecting the level of extrusion process. Most product structure dimensions and deviation values are clearly specified in the standard.
4.2. Smoothness: the surface of extruded insulating layer shall be smooth, and there shall be no bad quality problems such as surface roughness, scorching and impurities.
4.3. Densification: the cross section of extruded insulating layer shall be compact and solid, and there shall be no visible pinholes, and no bubbles.
For the multi-core cable, in order to ensure the molding degree and reduce the shape of the cable, it is generally necessary to twist it into a circle. The mechanism of stranding is similar to that of conductor stranding. Due to the large stranding pitch diameter, most of them adopt the non untwisting mode.
Technical requirements for cable forming: first, prevent twisting of cable caused by turning over of special insulation core; second, prevent the insulation layer from being scratched.
Most of the cables are completed along with the completion of the other two processes: one is filling to ensure the roundness and stability of the cables after completion; the other is binding to ensure that the cable core is not loose.
6 inner sheath
In order to protect the insulated wire core from being damaged by armor, the insulating layer needs to be properly protected. The inner protective layer consists of extruded inner protective layer (isolation sleeve) and wrapped inner protective layer (cushion). Wrapping cushion instead of binding belt shall be carried out synchronously with cable forming process.
Laying in the underground cable, the work may bear a certain positive pressure, can choose the inner steel belt armored structure. When the cable is laid in the situation of both positive pressure and tension (such as water, vertical shaft or soil with large drop), the structural type with inner steel wire armour shall be selected.
The outer sheath is a structural part to protect the insulation layer of wires and cables from environmental factors. The main function of the outer sheath is to improve the mechanical strength, chemical corrosion resistance, moisture-proof, water-proof and human immersion of the wires and cables, and prevent the cables from burning. According to the different requirements of the cable, the plastic sheath is directly extruded by the extruder.