Basic Knowledge Of Wires And Cables

Overview of wire and cable manufacturing process

The manufacturing method of wires and cables is completely different from that of most mechanical and electrical products. Mechanical and electrical products are usually assembled into parts by another part, and then assembled into a single product by multiple parts. The products are measured by the number of sets or pieces. The length of wires and cables is the basic unit of measurement. All wires and cables are made of wire and cable products by adding insulation, shielding, cabling, protective layers, etc. layer by layer on the periphery of the conductor from the conductor processing. The more complex the product structure is, the more layers are superimposed.

1、 Process characteristics of wire and cable manufacturing:

1. Large length continuous superposition combined production mode

The influence of large-length continuous superposition combination production mode on wire and cable production is global and controlling, which involves and affects:

(1) Production process flow and equipment layout

All kinds of equipment in the production workshop must be reasonably discharged according to the process flow required by the product, so that the semi-finished products in each stage can be transferred in sequence. Equipment configuration should consider different production efficiency to balance the production capacity. Some equipment may have to be configured with two or more to balance the production capacity of the production line. Therefore, the reasonable selection and combination of equipment and the layout of production site must be balanced and comprehensively considered according to products and production capacity.

(2) Production preparation management

The production preparation management must be scientific, reasonable, thorough, accurate, strict and meticulous. The operator must strictly implement the process requirements. Any problem in any link will affect the smoothness of the process flow and the quality and delivery of products. In particular, for multi-core cables, if the length of a pair or basic unit is short, or there is a quality problem, the length of the whole cable will be insufficient, resulting in scrapping. On the contrary, if the length of a unit is too long, it must be sawn away, causing waste.

(3) Quality management

The production mode of continuous superposition and combination of large length will cause a little problem in any link and instant in the production process, which will affect the quality of the whole cable. The more quality defects occur in the inner layer, and the greater the losses caused by not finding and terminating production in time. Because the production of wires and cables is different from that of assembled products, they can be disassembled, reassembled and replaced with other parts; The quality problem of any part or process of wire and cable is almost irretrievable and irreparable to this cable. The subsequent treatment is very negative, either sawing or degrading, or scrapping the whole cable. It cannot be disassembled and reassembled.

The quality management of wires and cables must run through the whole production process. The quality management and inspection department should carry out patrol inspection of the whole production process, self inspection of operators and mutual inspection of upper and lower processes, which is an important guarantee and means to ensure product quality and improve the economic benefits of enterprises.

2. There are many 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 technology such as wrapping and weaving of fiber materials, wrapping of metal materials, longitudinal wrapping of metal strips, metal forming and processing technology of welding, etc.

All kinds of materials used in the manufacture of wires and cables are not only of many types, varieties and specifications, but also in large quantities. Therefore, the consumption, standby consumption, batch cycle and batch of various materials must be verified. At the same time, the decomposition, recycling, reuse and waste disposal of waste products, as an important part of management, do a good job in material quota management and pay attention to saving.

In the production of wires and cables, from the import and export and storage of raw materials and various auxiliary materials, the circulation of semi-finished products in various processes to the storage and delivery of products, the material flow is large, so it must be reasonably arranged and dynamically managed.

3. Many special equipment

Wire and cable manufacturing uses special production equipment with the process 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, wire drawing machine series, stranding machine series, wrapping machine series, etc.

The manufacturing process of wires and cables is closely related to the development of special equipment and promotes each other. New process requirements to promote the emergence and development of new special equipment; In turn, the development of new special equipment has improved the promotion and application of new processes. Such as wire drawing, annealing, extrusion series line; Special equipment such as physical foaming production line has promoted the development and improvement of wire and cable manufacturing process, and improved the product quality and production efficiency of cables.

2、 Main process of wires and cables

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

1. Draw

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

Drawing process: monofilament drawing and stranding drawing.

2. Stranding

In order to improve the softness and integrity of wires and cables, interweaving more than two single wires in the specified direction is called stranding.

Stranding process is divided into: conductor stranding, cabling, weaving, steel wire armor and winding.

3. Coating

According to the different performance requirements of 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 package: rubber, wrinkled aluminum strip 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

3、 Basic technological process of plastic wire and cable manufacturing

1. Copper and aluminum monofilament drawing

The copper and aluminum rods commonly used for wires and cables can be reduced in section, increased in length and increased in strength by using a wire drawing machine through one or more die holes of the drawing 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

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

3. Stranding of conductors

In order to improve the softness of wires and cables and facilitate the laying and installation, the conductive wire core is twisted by multiple single wires. From the stranding form of conductor core, it can be divided into regular stranding and irregular stranding. Irregular stranding is also divided into bundle stranding, concentric compound stranding, special stranding, etc.

In order to reduce the occupied area of the conductor and reduce the geometric size of the cable, the form of compression is adopted while stranding the conductor, so that the ordinary circle changes into a semicircle, fan-shaped, tile shaped and compacted circle. This kind of conductor is mainly used in power cables.

4. Insulation extrusion

Extruded solid insulation layer is mainly used for plastic wires and cables. The main technical requirements of plastic insulation extrusion are as follows:

4.1 eccentricity: the deviation value of the extruded insulation thickness is an important sign of the extrusion process level. Most product structure dimensions and their deviation values are clearly specified in the standard.

4.2 smoothness: the surface of the extruded insulating layer shall be smooth, and there shall be no poor quality problems such as surface roughness, scorching and impurities

4.3. Densification: the cross section of the extruded insulating layer should be dense and solid, and there should be no visible holes, so as to prevent the existence of bubbles.

5. Cabling

For multi-core cables, in order to ensure the molding degree and reduce the shape of the cable, they generally need to be twisted into a circle. The mechanism of stranding is similar to that of conductor stranding. Because the stranding pitch diameter is large, most of them adopt the method of no untwisting. Technical requirements for cable forming: first, prevent the twisting of cables caused by turning over of special-shaped insulated cores; The second is to prevent the insulation layer from being scratched.

Most cables are completed with the completion of two other processes: one is filling, which ensures the roundness and stability of cables after cable completion; One 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 armor, it is necessary to properly protect the insulating layer. The inner protective layer is divided into: extruded inner protective layer (isolation sleeve) and wrapped inner protective layer (cushion). Wrapping cushion instead of binding belt is carried out synchronously with cabling process.

7. Armor

If the cable is laid underground, it may bear a certain positive pressure during work, and the inner steel strip armored structure can be selected. If the cable is laid in the place with both positive pressure and tension (such as in water, vertical shaft or soil with large drop), the structural type with inner steel wire armour shall be selected.

8. Outer sheath

The outer sheath is a structural part to protect the insulation layer of wires and cables from environmental factors. The main function of the outer sheath is to improve the mechanical strength, chemical corrosion prevention, moisture-proof, water-proof and human immersion of wires and cables, and prevent cable combustion. According to the different requirements of cables, the plastic sheath is directly extruded by the extruder.