Basic knowledge of wire and cable
Release time： 2021-12-31 17:58
Overview of wire and cable manufacturing process
The manufacture of wires and cables is quite different from the way most mechanical and electrical products are produced. Mechanical and electrical products usually adopt the assembly of another part into a component, a plurality of components and then assembly into a single product, the product is measured by the number of units or pieces. Wire and cable is the basic unit of measurement length. All wires and cables are made of wire and cable products by starting from conductor processing and adding insulation, shielding, cable forming and protective layer layer by layer on the periphery of the conductor. The more complex the product structure, the more layers there are.
1. Process characteristics of wire and cable product manufacturing:
1. Large length continuous superposition combination production mode
The large length continuous superposition combined production mode has a global and controlling influence on the production of wire and cable, which involves and affects:
(1) Production process and equipment layout
All kinds of equipment in the production workshop must be reasonably discharged according to the product requirements of the process flow, so that the semi-finished products of each stage, in turn. Equipment configuration should consider different production efficiency and production capacity balance, some equipment may have to be configured with two or more, in order to make the production capacity of the production line can be balanced. Therefore, the reasonable selection of equipment and the layout of the production site must be balanced according to the product and production capacity.
(2) Production organization and management
Production organization and management must be scientific and reasonable, thorough and accurate, strict and meticulous, the operator must be meticulous in accordance with the process requirements, any link problems, will affect the smooth process, affect the quality of products and delivery. Especially for multi-core cables, if the length of a cable pair or basic unit is short, or the quality problems occur, the length of the whole cable will be insufficient, resulting in scrap. Conversely, if a unit is too long, it must be sawed away for waste.
(3) Quality management
The large length continuous superposition combination production mode, so that any link in the production process, instantaneous problems will affect the quality of the whole cable. The more quality defects occur in the inner layer, and production is not detected and terminated in time, the greater the loss. Because the production of wire and cable is different from assembled products, it can be disassembled and reassembled and replaced with another part; The quality problems of any part or process of wire and cable are almost irreparable and irreparable for this cable. Afterwards, the treatment is very negative, either sawing or degrading, or scrapping the entire cable. It can't be taken apart and reassembled.
The quality control of wire and cable must run through the whole production process. Quality management inspection department to the whole production process inspection tour, operator self-inspection, upper and lower procedures mutual inspection, which is to ensure product quality, improve the economic benefits of enterprises an important guarantee and means.
2. There are many kinds of production technology and large flow of materials
Wire and cable manufacturing involves a wide range of processes, from non-ferrous metal smelting and pressure processing, to plastics, rubber, paint and other chemical technology; Fiber material wrapping, weaving and other textile technology, to metal material wrapping and metal strip longitudinal wrapping, welding metal forming processing technology and so on.
Wire and cable manufacturing of various materials, not only category, variety, specifications, and large quantity. Therefore, the amount of various materials, reserve amount, batch cycle and batch must be approved. At the same time, the waste decomposition, recycling, reuse and waste treatment, as an important content of management, do a good job of material quota management, pay attention to saving work.
In the production of wire and cable, from the entry and exit and storage of raw materials and various auxiliary materials, the flow of semi-finished products in each process to the storage and delivery of products, the material flow is large, must be reasonable layout, dynamic management.
3. Special equipment
Wire and cable manufacturing uses special production equipment with the characteristics of the industry process, in order to adapt to the structure and performance requirements of cable products, to meet the requirements of large length continuous and as high speed production as possible, thus forming a series of special equipment for cable manufacturing. Such as extruder series, drawing machine series, stranding machine series, winding machine series, etc.
The manufacturing process of wire and cable and the development of special equipment are closely related and promote each other. New process requirements to promote the generation and development of new special equipment; In turn, the development of new special equipment, and promote the promotion and application of new technology. Such as wire drawing, annealing, extrusion series line; Physical foaming production line and other special equipment, promote the development and improvement of wire and cable manufacturing technology, improve the cable product quality and production efficiency.
Two, the main process of wire and cable
Wires and cables are made by drawing, twisting and coating. The more complex the specifications, the higher the repeatability.
In metal pressure working. The metal is forced through the die (press wheel) under the action of external forces, the cross-sectional area of the metal is compressed, and the required cross-sectional area shape and size of the technical processing method is called metal drawing.
Drawing process: single wire drawing and hinge drawing.
In order to improve the softness and overall degree of wire and cable, more than 2 single wires are interwoven together in accordance with the prescribed direction.
The stranding process includes conductor stranding, cable forming, braiding, steel wire armoring and winding.
According to the different performance requirements of wire and cable, special equipment is used to coat the conductor with different materials. Coating process:
A. Extrusion: rubber, plastic, lead, aluminum and other materials.
B. Longitudinal wrap: rubber, corrugated aluminum tape material.
C. Wrapping: ribbon paper tape, mica tape, alkali free glass fiber tape, non-woven fabric, plastic tape, linear cotton yarn, silk and other fiber materials.
D. Dip coating: insulating paint, asphalt, etc
Three, the basic process of plastic wire and cable manufacturing
1. Copper and aluminum monofilament drawing
Wire and cable commonly used copper, aluminum rod, at room temperature, the use of wire drawing machine through one or several ways to stretch the die hole of the mold, so that its section is reduced, the length is increased, the strength is improved. Wire drawing is the first process of each wire and cable company, the main process parameter of wire drawing is the mold technology.
2. Monofilament annealing
Copper and aluminum monofilaments are heated to a certain temperature and recrystallized to improve the toughness and reduce the strength of the monofilaments, in order to meet the requirements of wire and cable for conductive core. The key of annealing process is to prevent the oxidation of copper wire.
3. Stranding of conductors
In order to improve the softness of the wire and cable, so as to facilitate the installation, the conductive wire core is twisted by several single wires. From the form of stranded conductor core, can be divided into regular stranded and irregular stranded. Irregular stranding is divided into bundle stranding, concentric double stranding, special stranding, etc.
In order to reduce the occupied area of the wire and reduce the geometric size of the cable,
When the conductor is stranded, the compact form is used, so that the ordinary circle is changed into semicircle, fan, tile shape and compact circle. This conductor is mainly used in power cables.
4. Insulating extrusion
Plastic wire and cable mainly use extruded solid insulation layer, plastic insulation extrusion main technical requirements:
4.1. Eccentricity: the deviation value of extruded insulation thickness is an important symbol of the extrusion process level, most of the product structure size and its deviation value are clearly specified in the standard.
4.2. Smoothness: the surface of the extruded insulation layer should be smooth, and there should be no bad quality problems such as rough surface, burning and impurities
4.3. Density: the cross section of the extruded insulation layer shall be dense and firm, and no visible pinholes shall be allowed to eliminate the existence of bubbles.
For the multi-core cable in order to ensure the degree of molding, reduce the shape of the cable, generally need to twist it into a circle. The mechanism of stranding is similar to that of conductor stranding. Because of the large joint diameter of stranding, most of the stranding methods are used without torsion. The technical requirements of cable forming: first, it is to prevent the twisting and bending of the cable caused by turning over the special-shaped insulated wire core; The second is to prevent the insulation layer from being scratched.
Most cables are completed with two other processes: one is filling to ensure the roundness and stability of cables; One is to tie, to ensure that the cable core is not loose.
6. Inner sheath
In order to protect the insulating core from being sheathed, the insulating layer is required to be properly protected. The inner sheathing is divided into extruded inner sheathing (isolation sheath) and wrapped inner sheathing (cushion). The wrapping pad is synchronized with the cabling process instead of the lashing tape.
The underground cable may bear a certain positive pressure during the work, so the inner steel tape armored structure can be selected. Cable laying in both positive pressure and tension effect of the occasion (such as water, vertical shaft or large drop in the soil), should be selected with internal steel wire armored structure.
8. Outer sheath
The outer sheath is the part of the structure that protects the insulation layer of the wire and cable from environmental factors. The main function of the outer sheath is to improve the mechanical strength of the wire and cable, prevent chemical corrosion, moisture-proof, waterproof immersion, prevent cable burning and so on. According to the different requirements of cable using extruder directly extruded plastic sheath.