The Basic Knowledge of Wire And Cable

The manufacture of wire and cable is completely different from the production of most electromechanical products. Mechanical and electrical products are usually assembled into components, and multiple components are assembled into a single product, and the product is measured by the number of units or pieces. Wire and cable are based on length as the basic unit of measurement. All wires and cables start from conductor processing, and then add insulation, shielding, cabling, sheathing, etc. layer by layer on the periphery of the conductor to make wire and cable products. The more complex the product structure, the more layers are superimposed.

一. Process characteristics of wire and cable product manufacturing:

1. Large-length continuous stacking combination production method

The large-length continuous stacking combined production method has a global and controllable impact 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 technological process required by the product, so that the semi-finished products at each stage can be circulated in sequence. The equipment configuration should consider the different production efficiency and balance the production capacity. Some equipment may have to be equipped with two or more sets to balance the production capacity of the production line. Therefore, the reasonable selection and 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 and management must be scientific, reasonable, thorough, accurate, and strict. Operators must follow the process requirements meticulously. Any problem in any link will affect the smooth process flow and affect product quality and delivery. Especially for multi-core cables, if the length of a certain line pair or basic unit is short, or if there is a quality problem, the entire cable will not be long enough, resulting in scrapping. Conversely, if a unit is too long, it must be sawn off to cause waste.

(3) Quality management

The production method of continuous superposition and combination of large lengths makes any momentary problem in any link in the production process affect the quality of the entire cable. The more quality defects occur in the inner layer, and the production is not found out in time, the greater the loss will be. Because the production of wires and cables is different from assembled products, they can be disassembled, reinstalled and replaced; the quality problems of any part or process of wires and cables are almost irreparable and irreparable for this cable. The aftermath solutions are very depressing, either sawing short or returning to treatment, or scrapping a cable. It cannot be disassembled and reassembled.

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

2. There are many types of production processes and 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 paint; textile technologies such as wrapping and weaving of fiber materials, to wrapping of metal materials and metal strips Longitudinal package, welding metal forming process and so on.

The various materials used in the manufacture of wires and cables not only have many types, varieties, and specifications, but also a large number. Therefore, the consumption, spare quantity, batch cycle and batch size of various materials must be approved. At the same time, as an important content of management, the decomposition, recycling, recycling and waste disposal of waste products should be done well in the management of material quotas and emphasis on conservation.

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 flow of materials is large, which must be rationally arranged and dynamically managed.

3. Many special equipment

Wire and cable manufacturing uses special production equipment with the technical characteristics of the industry to meet the structure and performance requirements of cable products and meet the requirements of large-length continuous and high-speed production as much as possible, thus forming a series of special equipment for cable manufacturing. Such as extruder series, drawing machine series, stranding machine series, wrapping machine series, etc.

The manufacturing process of wire and cable is closely related to the development of special equipment and promotes each other. New process requirements promote the production and development of new special equipment; in turn, the development of new special equipment promotes the promotion and application of new processes. Special equipment such as wire drawing, annealing, extruding serial lines; physical foaming production lines, etc., have promoted the development and improvement of wire and cable manufacturing processes, and improved the product quality and production efficiency of cables.

二, The main process of wire and cable

Wires and cables are manufactured through three processes: drawing, twisting, and coating. The more complex the model specification, the higher the repeatability.

1. Drawn

In metal pressure processing. Under the action of external force, the metal is forced to pass through the mold (press wheel), the metal cross-sectional area is compressed, and the technical processing method to obtain the required cross-sectional area shape and size is called metal drawing.

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

2. Stranded

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

The stranding process is divided into: conductor stranding, cabling, braiding, steel wire armoring and winding.

3. Clad

According to different performance requirements for wires and cables, 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． Longitudinal bag: rubber, corrugated aluminum tape material.

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

D． Dip coating: insulating varnish, asphalt, etc.

三. The basic technological process of plastic wire and cable manufacturing

1. Copper, aluminum monofilament drawing

Commonly used copper and aluminum rods for wires and cables, at room temperature, use a wire drawing machine to pass through one or several die holes of the drawing die to reduce the cross section, increase the length and improve the strength. Wire drawing is the first process of each wire and cable company, and the main process parameter of wire drawing is mold matching technology.

2. Monofilament annealing

When the copper and aluminum monofilaments are heated to a certain temperature, the toughness of the monofilaments is improved and the strength of the monofilaments is reduced by means of recrystallization, so as to meet the requirements of electric wires and cables for conductive cores. The key to the annealing process is to prevent the oxidation of the copper wire.

3. Stranding of conductors

In order to improve the softness of wires and cables and facilitate laying and installation, the conductive core is made of multiple monofilaments twisted. From the stranding form of the conductive core, it can be divided into regular stranding and irregular stranding. Irregular stranding is divided into beam stranding, concentric stranding, special stranding, etc.

In order to reduce the occupied area of the wires and reduce the geometric size of the cable, the compact form is adopted while the conductor is stranded, so that the ordinary circle is mutated into a semicircle, a fan shape, a tile shape and a tightly pressed circle. This kind of conductor is mainly used in power cables.

4. Insulation extrusion

Plastic wire and cable mainly use extruded solid insulation layer. The main technical requirements for plastic insulation extrusion:

4.1. Eccentricity: The deviation value of the extruded insulation thickness is an important indicator of the extrusion process level. Most of the product structure size and its deviation value are clearly stipulated in the standard.

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

4.3. Density: The cross-section of the extruded insulating layer should be dense and firm, without pinholes visible to the naked eye, and to prevent the existence of air bubbles.

5. Cabling

For multi-core cables, in order to ensure the formability and reduce the shape of the cables, it is generally necessary to twist them into a circular shape. The mechanism of stranding is similar to that of conductor stranding. Due to the large pitch diameter of stranding, most of them adopt the non-back twisting method. Technical requirements for cabling: one is to prevent twisting and bending of the cable caused by the overturning of special-shaped insulated cores; the other is to prevent the insulation layer from being scratched.

Most of the cables are cabled together with the completion of two other processes: one is filling to ensure the roundness and stability of the cable after cable forming; 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 the armor, it is necessary to properly protect the insulation layer. The inner sheath is divided into: extruded inner sheath (isolation sleeve) and wrapped inner sheath (cushion). The wrapping cushion instead of the binding tape is carried out simultaneously with the cable forming process.

7. Armor

Cables laid underground may bear a certain amount of positive pressure during work, and the inner steel tape armored structure can be selected. When the cable is laid in the occasion with both positive pressure and tension (such as in water, vertical shaft or soil with large drop), the structure type with inner steel wire armor should be selected.

8. Outer sheath

The outer sheath is a structural part 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, chemical corrosion resistance, moisture resistance, water immersion, and the ability to prevent the cable from burning. According to the different requirements of the cable, the plastic sheath is directly extruded by the extruder.