The main process of wire and cable

Release date: 2021/5/11 15:51:40 | Publisher: Shenzhen Cptele Electronics Co., Ltd

 

Wires and cables are made through three processes: drawing, twisting and coating, and the more complex the model specifications, the higher the repeatability.

1. Pulling

In metal pressure machining. The technical processing method of forcibly passing the metal through the die (pressure wheel) under the action of external force, the metal cross-sectional area is compressed, and the shape and size of the required cross-sectional area are obtained.

The drawing process is divided into: monofilament drawing and stranding drawing.

2. Stranding

In order to improve the flexibility and integrity of wires and cables, two or more single wires are intertwined in a specified direction, which is called stranding.

Stranding process is divided into: conductor stranding, cable formation, braiding, steel wire armor and winding.

3. Wrapping

According to the different performance requirements of wires and cables, special equipment is used to coat the conductor with different materials. Coating process is divided into:

A. Extruded bag: rubber, plastic, lead, aluminum and other materials.

B. Longitudinal bag: eraser, wrinkled aluminum strip material.

C. Wrapping: ribbon-like paper tape, mica tape, alkali-free glass fiber tape, non-woven fabric, plastic tape, etc., linear cotton yarn, silk and other fiber materials.

D． Dip coating: insulating paint, asphalt, etc

Third, the basic process of plastic wire and cable manufacturing

1. Copper and aluminum monofilament drawing

Copper and aluminum rods commonly used in wires and cables are used to reduce the cross-section, increase the length and improve the strength of the wire drawing machine through one or more die holes of the stretching die at room temperature. Wire drawing is the first process of wire and cable companies, and the main process parameter of wire drawing is mold matching technology.

2. Monofilament annealing

Copper and aluminum monofilaments are heated to a certain temperature to improve the toughness of the monofilament and reduce the strength of the monofilament by recrystallization, so as to meet the requirements of wires and cables for conductive cores. The key to the annealing process is to eliminate the oxidation of copper wire.

3. Stranding of conductors

In order to improve the flexibility of wires and cables and facilitate laying and installation, the conductive wire core is made of multiple monofilaments stranded. From the form of stranding of conductive cores, it can be divided into regular stranding and irregular stranding. Irregular stranding is divided into bundle stranding, concentric double twisting, special stranding, etc.

In order to reduce the occupied area of the wire and reduce the geometric size of the cable, the compression form is adopted while the conductor is stranded, so that the ordinary circle is changed into a semicircle, a fan, a tile shape and a compacted circle. This type of conductor is mainly used in power cables.

4. Insulation extrusion

Plastic wires and cables are mainly extruded solid insulation, and the main technical requirements of plastic insulation extrusion:

4.1. Eccentricity: The deviation value of the insulation thickness of extrusion is an important indicator of the level of extrusion process, and most of the product structure dimensions and their deviation values are clearly specified in the standard.

4.2. Smoothness: The surface of the extruded insulating layer is required to be smooth, and there shall be no poor quality problems such as rough surface, scorching and impurities

4.3. Density: The cross-section of the extruded insulation layer should be dense and firm, and there should be no pinholes visible to the naked eye, so as to prevent the existence of bubbles.

5. Cable

For multi-core cables, in order to ensure the degree of formability and reduce the shape of the cable, it is generally necessary to twist them into a circle. The stranding mechanism is similar to that of conductor stranding, and most of them adopt a non-twist retreat method due to the large diameter of the stranding joint. Technical requirements for forming cables: first, to prevent the twisting of the cable caused by the turning over of the special-shaped insulated core; The second is to prevent the insulation from being scratched.

Most of the cables are accompanied by the completion of two other processes at the same time as the cable: one is filling to ensure the roundness and stability of the cable after the cable; One is the lashing to ensure that the cable core is not loose.

6. Inner sheath

In order to protect the insulating wire core from being damaged by the armor, it is necessary to properly protect the insulating layer, and the inner sheath is divided into: extruded inner sheath (isolation sleeve) and wrapped inner sheath (cushion). The wrapping cushion replaces the lashing belt and is synchronized with the cabling process.

7. Armor

Laying in the underground cable, the work may bear a certain positive pressure effect, can choose the inner steel belt armored structure. When the cable is laid in the occasion of both positive pressure and tensile force (such as in water, vertical shaft or soil with large drop), the structural type with internal steel wire armor should be selected.

8. Outer sheath

The outer sheath is the structural part of the insulation that protects the wire and cable from environmental factors. The main function of the outer sheath is to improve the mechanical strength of wires and cables, anti-chemical corrosion, moisture-proof, waterproof and immersive, and prevent cable combustion. According to the different requirements of the cable, the plastic sheath is directly extruded by an extruder.

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