Power cords are produced every day. More than 100,000 meters of power cords and 50,000 plugs are produced every day. For such huge data, the production process must be very stable and mature. After continuous exploration and research and recognition by the European VDE certification agency, the national CCC certification agency, the American UL certification agency, the British BS certification agency, the Australian SAA certification agency, etc., the power cord plug has matured. Here is an introduction:
1. Power cord drawn from copper and aluminum single wire
Copper and aluminum rods commonly used in power cords are passed through the die holes of one or several drawing molds using a wire drawing machine at room temperature to reduce their cross-section, increase their length, and improve their strength. Wire drawing is the first process of every wire and cable company, and the main process parameter of wire drawing is the mold matching technology.
2. Monofilament annealing of power cord
When copper and aluminum monofilaments are heated to a certain temperature, they recrystallize to improve the toughness of the monofilaments and reduce the strength of the monofilaments to meet the requirements of wires and cables for conductive cores. The key to the annealing process is to eliminate oxidation of the copper wire.
3. Twisting of power cord conductors
In order to improve the flexibility of the power cord and facilitate laying and installation, the conductive core is made of multiple monofilaments twisted together. From the stranding method of conductive wire cores, it can be divided into regular stranding and non-regular stranding. Non-regular twisting is divided into bundle twisting, concentric twisting, special twisting, etc. In order to reduce the area occupied by the wire and reduce the geometric size of the power cord, the stranded conductor is also pressed to make the ordinary round shape transform into a semicircle, a sector shape, a tile shape and a pressed round shape. This type of conductor is mainly used in power lines.
4. Power cord insulation extrusion
Plastic power cords mainly use extruded solid insulation layers. The main technical requirements for plastic insulation extrusion are:
1) Deviation: The deviation value of the extruded insulation thickness is an important indicator of the level of extrusion workmanship. Most product structural dimensions and their deviation values have clear regulations in the standards.
2) Lubricity: The surface of the extruded insulation layer must be lubricated, and there must be no poor quality problems such as rough surface, burnt surface, or impurities.
3) Density: The cross-section of the extruded insulation layer must be dense and strong, with no pinholes visible to the naked eye and no bubbles.
5. Connect the power cord
For multi-core power cords, in order to ensure molding and reduce the shape of the power cord, it is generally necessary to twist them into a circle. The mechanism of stranding is similar to that of conductor twisting. Because the pitch diameter of the twisting is large, most methods without back twisting are used. The technical requirements for cabling: first, to prevent the abnormally shaped insulated core from turning over and causing the cable to twist; second, to prevent the insulation layer from being scratched.
The cabling of most cables is accompanied by the completion of two other processes: one is filling to ensure the roundness and stability of the cable after cabling; the other is binding to ensure that the cable core is not loose.
6. Inner protective layer of power cord
In order to protect the insulated core from being damaged by the armor, the insulation layer needs to be properly protected. The inner sheath is divided into: extruded inner sheath (isolation sleeve) and wrapped inner sheath (cushion). The wrapping cushion replaces the binding tape and is carried out simultaneously with the cabling process.
7. Power cord armoring
It is laid in underground power lines and can withstand certain positive pressure effects during operation. The inner steel tape armored structure can be selected. The power cord is laid in a place with both positive pressure and tension effects (such as water, vertical shafts or soil with a large drop), and the selector should have an internal steel wire armored structure.
8. Power cord outer sheath
The outer sheath is the structural part that protects the insulation layer of the power cord from corrosion due to environmental factors. The main function of the outer sheath is to improve the mechanical strength of the power cord, prevent chemical corrosion, moisture-proof, waterproof and immersion, and prevent the power cord from burning. According to the different requirements for the power cord, an extruder is used to directly extrude the plastic sheath.