Basic Knowledge of Worn-out Wires and Cables

The manufacturing process for wire and cable is fundamentally different from that of most electromechanical products. Electromechanical products typically involve assembling components into sub-assemblies, and then multiple sub-assemblies into a single product, which is measured by the number of units or pieces. Wire and cable products are measured by length. All wire and cable products begin with the processing of conductors, where layers of insulation, shielding, cabling, and sheathing are added around the conductor to form the final product. The more complex the product structure, the greater the number of layers stacked.

I. Process characteristics of wire and cable product manufacturing:

1. Continuous long-length composite production method

The large-length continuous stacking and assembly production method has a global and controlling impact on the production of wires and cables, involving and affecting:

(1) Production Process and Equipment Layout

The various equipment in the production workshop is arranged in a fair sequence according to the product's process requirements, ensuring the sequential flow of semi-finished products. The equipment configuration takes into account the varying production efficiency to balance production capacity, with some equipment possibly requiring two or more units to achieve balanced production line capacity. Consequently, the fair selection and combination of equipment, as well as the layout of the production site, are comprehensively balanced based on the product and production volume.

(2) Production Organization Governance

Our production organization is governed by scientific, fair, thorough, and precise management. Operators meticulously adhere to the process requirements. Any issue at any stage can disrupt the smooth flow of the production process, affecting product quality and delivery. Particularly in the case of multicore cables, if a pair of wires or a basic unit is too short, or if there is a quality issue, the entire cable will be insufficient in length, resulting in scrapping. Conversely, if a unit is excessively long, it would be cut off, leading to waste.

(3) Quality Management

The production method of large-length continuous叠加 combinations means that any issue at any stage or instant during the manufacturing process can affect the entire cable's quality. The greater the quality defects occur in the inner layers, and the longer they go undetected and unaddressed, the greater the resulting loss. Unlike assembly-style products, the production of wires and cables cannot be disassembled, reassembled, or replaced with parts; any quality issue with a component or process in the cables is nearly irreparable. Post-production remedies are highly negative, often involving shortening the cable, downgrading it, or even scrapping the entire cable. It cannot be disassembled and reassembled.

Quality control of electrical wires and cables is integrated throughout the entire production process. The quality control team conducts routine inspections, operator self-inspections, and inter-process inspections to ensure product quality and enhance the economic benefits of the enterprise.

2. A wide range of production processes and a large material flow

The manufacturing of wire and cable involves a wide range of processes, from the melting and pressure processing of non-ferrous metals, to chemical technologies such as plastics, rubber, and paints; from textile techniques like winding and weaving of fiber materials, to metal forming processes such as wrapping of metals and longitudinal wrapping and welding of metal strips.

The materials used in the manufacturing of electrical wires and cables are not only diverse in types, varieties, and specifications but also in quantity. Consequently, careful consideration is given to the usage, reserve quantities, and batch cycles of these materials, as well as the batching specifications. Additionally, the decomposition and treatment of waste products, recycling, reuse, and waste disposal are important aspects of management. Efforts are made to implement material quota management and emphasize the importance of conservation.

In the production of electrical wires and cables, the material flow is significant, requiring fair layout and dynamic management from the procurement and storage of raw materials and various auxiliary materials, through the circulation of semi-finished products in various processes, to the storage and dispatch of finished products.

3. A wide range of dedicated equipment

Cable and wire manufacturing equipment features specialized production machinery with industry-specific process characteristics to accommodate the structural and functional requirements of cable products. It meets the demands for continuous production over long lengths at as high a speed as possible, thereby forming a series of specialized equipment for cable manufacturing. This includes extrusion machines, wire drawing machines, stranding machines, and winding machines, among others.

The manufacturing process of wire and cable is closely related to the development of specialized equipment, fostering mutual advancement. New processes necessitate the creation and development of new specialized equipment; conversely, the development of new specialized equipment further promotes the popularization and application of new processes. Equipment such as drawing, annealing, and extrusion lines; physical foaming production lines, etc., have promoted the development and progress of wire and cable manufacturing processes, enhancing cable product quality and production efficiency.

Section II: Main Processes of Wires and Cables

Cable wires are manufactured through three processes: drawing, twisting, and sheathing. The more complex the model and specifications, the higher the repeatability.

1. Drawn

In metal pressure processing, the technique of forcing metal through dies (pressure rolls) under external force, compressing its cross-sectional area, and achieving the required cross-sectional shape and dimensions is called metal drawing.

Pulling process: Single fiber pulling and twisted pulling.

Twisting

To enhance the flexibility and uniformity of wire and cable, multiple single wires are intertwined together in a designated direction, a process known as twisting.

Texturing processes: conductor texturing, cabling, braiding, wire armor and wrapping entanglement.

3. Encapsulation

According to the diverse functional requirements for electrical wires and cables, different materials are coated over the conductors using specialized equipment. The coating processes are categorized as follows:

A. Extruded products: Materials such as rubber, plastic, lead, and aluminum.

B. Coated Yarn: Rubber, embossed aluminum strip materials.

Coating Wraps: Striped paper tape, mica tape, alkali-free glass fiber tape, non-woven fabric, plastic tape, linear cotton yarn, silk, and other fiber materials.

D. Coating: Insulating paint, asphalt, etc.

Basic Process Flow of Plastic Wire and Cable Manufacturing

Copper and aluminum single wire drawing

Copper and aluminum rod materials commonly used in wire and cable production are stretched through one or more die holes of a drawing machine at room temperature, resulting in reduced cross-section, increased length, and improved strength. Drawing is the first process in the manufacturing of all wire and cable companies, with die matching technology being the primary process parameter.

2. Annealed monofilament

Copper and aluminum single wires are heated to a certain temperature to improve their toughness and reduce their strength through the process of recrystallization, in order to meet the requirements of wire and cable conductors. The key to the annealing process is to prevent oxidation of the copper wire.

3. Conductor Twisting

To enhance the flexibility of electrical cables for easier installation, the conductor cores are made from multiple single filaments twisted together. The twisting patterns of the conductor cores can be categorized into regular and irregular twisting. Irregular twisting includes strand twisting, concentric lay twisting, and special twisting, among others.

To minimize the occupied area of conductors and reduce the geometric dimensions of cables, a tight pressing form is adopted during the twisting of the conductors, transforming the ordinary circular shape into semi-circular, sector, tile-like, and tightly pressed circular shapes. This type of conductor is primarily used in power cables.

4. Insulation Extrusion

Plastic insulated wire and cable mainly use solid-core insulation. The primary technical requirements for the extrusion of plastic insulation:

4.1 Eccentricity: The deviation value of the extruded insulating thickness is an important indicator of the extrusion process level. Most product structures and their deviation values are clearly defined within the dimensions.

4.2. Smoothness: The extruded insulation layer must have a smooth surface without any roughness, scorching, or impurities.

4.3. Density: The cross-section of the extruded insulation layer must be compact and solid, free from any visible joints or bubbles.

5. Cable Manufacturing

To ensure the shape and reduce the cable's profile, multi-core cables are typically twisted into a circular shape. The twisting mechanism is similar to conductor twisting, as the pitch is larger, usually employing a non-reversing twist method. Technical requirements for cable formation include: 1) preventing the twist of non-standard insulated cores from causing cable twists; 2) preventing the insulation layer from being scratched.

During the cable manufacturing process, the large department cables are accompanied by the completion of two additional工序: one is filling, which ensures the roundness and orderliness of the cable after it is made; the other is binding, which ensures that the cable core is not loose.

6. Inner sheath

To protect the insulated core from being damaged by the armor, appropriate protection for the insulation is required. The inner sheath is divided into: extruded inner sheath (insulating sleeve) and wrapped inner sheath (padding layer). The wrapped padding layer replaces the binding tape and is performed simultaneously with the cable-making process.

7. Armor Installation

Underground cable laying may be subjected to certain positive pressure during operation, and an inner steel tape armor structure can be selected. For cable laying scenarios where both positive pressure and tensile forces are present (such as in water, vertical shafts, or in soil with significant drop), equipment with an inner steel wire armor structure should be chosen.

Outer Sheath

The outer sheath is a structural component that protects the insulation of wires and cables from environmental corrosion. The primary function of the outer sheath is to enhance the mechanical strength, chemical resistance, moisture resistance, waterproofing, and flame-retardant capabilities of the wires and cables. Depending on the specific requirements for the cables, a plastic sheath is directly extruded using an extruder.