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    Wire and cable basics

    Joca 2018-10-22 1833hit return

    Wire and cable manufacturing process overview


    The manufacture of wire and cable is completely different from the way most electromechanical products are produced. Electromechanical products are usually assembled into parts, multiple parts and assembled into a single product, which is measured in number or number of pieces. Wire and cable are based on length. All wire and cable are made from the processing of conductors, and the wires and cables are made by adding insulation, shielding, cable-forming, sheathing, etc. layer by layer on the outer periphery of the conductor. The more complex the product structure, the more layers are stacked.


    First, the process characteristics of wire and cable product manufacturing:


    1. Large length continuous stacking combined production method


    The large-scale continuous superposition combined production mode has a global and control effect 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 discharged according to the technical process required by the product, so that the semi-finished products in each stage can be transferred in sequence. The equipment configuration should balance the production capacity in consideration of different production efficiencies. Some equipments may have to be configured with two or more units in order to balance the production capacity of the production line. Therefore, the reasonable combination of equipment and the layout of the production site must be balanced and comprehensively considered according to the product and production volume.


    (2) Production organization management


    Production organization management must be scientific and reasonable, thorough and accurate, strict and meticulous, operators must be meticulously implemented according to the process requirements, any problem in one link will affect the smooth flow of the process, affecting the quality and delivery of the product. Especially for multi-core cables, if the length of a certain pair or basic unit is short, or if there is a problem with the quality, the length of the entire cable will be insufficient, resulting in scrapping. Conversely, if a unit is too long, it must be sawed to cause waste.


    (3) Quality management


    The production method of continuous stacking of large lengths causes any problem in the production process and instantaneously, which will affect the quality of the whole cable. The more the quality defects occur in the inner layer, and the production is not discovered in time, the greater the loss. Because the production of wire and cable is different from the assembled product, it can be disassembled and replaced; the quality of any part of the wire and cable or the process is almost irreparable and compensated for. The after-the-fact processing is very negative, not short-cutting or downgrading, or scrapping the entire cable. It cannot be disassembled and reassembled.


    The quality management of wire and cable must be consistent throughout the production process. The quality management inspection department shall conduct inspections of the entire production process, self-inspection of the operators, and mutual inspection of the upper and lower processes. This is an important guarantee and means to ensure product quality and improve the economic benefits of the enterprise.


    2. More production processes, large material flow


    Wire and cable manufacturing involves a wide range of processes, from smelting and pressure processing of non-ferrous metals to chemical technologies such as plastics, rubber and paints; textile technology for wrapping and weaving of fiber materials, wrapping of metal materials and metal strips. Longitudinal package, welded metal forming process, etc.


    Various materials used in wire and cable manufacturing are not only in categories, varieties, and specifications, but also in large quantities. Therefore, the amount of materials used, the amount of spare, the batch cycle and the batch must be verified. At the same time, the decomposition, recycling, recycling and waste disposal of waste products, as an important part of management, do a good job in material quota management and pay attention to conservation work.


    In the production of wire and cable, from the entry and exit 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, and must be rationally arranged and dynamically managed.


    3. More dedicated equipment


    Wire and cable manufacturing uses special production equipment with the characteristics of the industry to meet the structural and performance requirements of cable products, to meet the requirements of large length continuous and as fast as possible, thus forming a series of special equipment for cable manufacturing. Such as extrusion machine series, wire drawing machine series, stranding machine series, winding machine series.


    The manufacturing process of wire and cable is closely related to the development of special equipment and promotes each other. New process requirements to promote the generation and development of new special equipment; in turn, the development of new special equipment has promoted the promotion and application of new technologies. Such as drawing, annealing, extrusion series line; physical foam production line and other special equipment, promote the development and improvement of wire and cable manufacturing process, improve cable product quality and production efficiency.


    Second, the main process of wire and cable


    Wire and cable are made by three processes: drawing, twisting and cladding. The more complex the model specifications, the higher the repeatability.


    1. Drawing


    In metal press processing, a technical processing method in which a metal is forced to pass through a mold (pressure roller) under an external force, a metal cross-sectional area is compressed, and a desired cross-sectional area shape and size is obtained is called metal drawing.


    Drawing process: single wire drawing and strand drawing.


    2. Twist


    In order to improve the softness and integrity of the wire and cable, it is called twisting by interlacing two or more single wires in a predetermined direction.


    Twisting process: conductor stranding, cabling, weaving, wire mounting and winding.


    3. Coated


    Depending on the different performance requirements of the wire and cable, special equipment is used to coat different materials on the outside of the conductor. Coating process points:


    A. Extrusion: rubber, plastic, lead, aluminum and other materials.


    B. Vertical package: rubber, corrugated aluminum strip material.


    C. Wrap: tape-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 varnish, asphalt, etc.


    Third, the basic process of plastic wire and cable manufacturing


    1. Copper and aluminum monofilament drawing


    Commonly used copper and aluminum rods for wire and cable, at room temperature, use a wire drawing machine to stretch the die hole of one or several passes, so that the cross section is reduced, the length is increased, and the strength is improved. Drawing is the first process of wire and cable companies. The main process parameters of wire drawing are mold matching technology.


    2. Monofilament annealing


    Copper and aluminum monofilaments are heated to a certain temperature to re-crystallize the toughness of the monofilament and reduce the strength of the monofilament to meet the requirements of the wire and cable for the conductive core. The key to the 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, in order to facilitate the installation and installation, the conductive core is formed by twisting a plurality of monofilaments. From the twisted form of the conductive core, it can be divided into regular stranding and irregular stranding. Irregular stranding is further divided into bunching, concentric twisting, special stranding, and the like.


    In order to reduce the occupied area of the wire and reduce the geometrical size of the cable, the twisted form is used while twisting the conductor, so that the ordinary circular variation is a semicircle, a fan shape, a tile shape and a compact circular shape. This type of conductor is mainly used on power cables.


    4. Insulation extrusion


    Plastic wire and cable mainly adopts solid insulation type with extruded rubber. The main technical requirements for plastic insulation extrusion are:


    4.1. Eccentricity: The deviation of the thickness of the extruded insulation is an important indicator of the level of the extrusion process. Most of the product structure dimensions and their deviation values are clearly defined in the standard.


    4.2. Smoothness: The surface of the extruded insulation layer is required to be smooth, and there must be no problem of poor quality of surface roughness, charring and impurities.


    4.3. Density: The cross section of the extruded insulation layer should be dense and strong, and pinholes visible to the naked eye should not be allowed to prevent the presence of air bubbles.


    5. Cable


    For multi-core cables, in order to ensure the degree of molding and reduce the shape of the cable, it is generally required to be twisted into a circular shape. The mechanism of stranding is similar to that of conductor stranding. Due to the large diameter of the stranding, most of the twisting is used. Technical requirements for cable-forming: First, to prevent the twisted corner of the cable caused by the turning of the special-shaped insulated wire core; the second is to prevent the insulating layer from being scratched.


    Most of the cables are cabled along with the completion of two other processes: one is filling, ensuring roundness and stability of the cable after cable is formed; one is tying to ensure that the cable core is not loose.


    6. Inner sheath


    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 an inner sheath (isolation sleeve) and a inner sheath (cushion). Substituting the wrap layer in place of the tie wrap is performed in synchronization with the cabling process.


    7. Decoration


    It is laid on the underground cable and may be subjected to a certain positive pressure during work. The inner steel belt armor structure can be selected. When the cable is laid in a place with both positive pressure and tensile force (such as water, vertical shaft or soil with large drop), the structure with inner steel wire armor should be selected.


    8. Outer sheath


    The outer sheath is a structural part that protects the insulation 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, chemical corrosion resistance, moisture resistance, water immersion, and the ability to prevent cable burning. The plastic sheath is directly extruded using an extruder according to the different requirements of the cable.