What is the production process of control cables?

The production process of control cables is a multi-link and high-precision manufacturing process. It needs to combine requirements such as electrical performance, mechanical strength and environmental adaptability, and achieve the transformation from raw materials to finished products through a systematic process. The following is a detailed analysis of its core steps and technical key points from the perspective of the entire process flow:

I. Raw material Preparation Stage

Conductor processing

Material selection and testing: High-purity electrolytic copper (copper content ≥99.95%) or aluminum alloy is selected. The impurity content (oxygen content in copper < 0.02%) is confirmed through spectral analysis, and the resistivity of the conductor is tested (copper conductor ≤0.017241Ω · mm²/m at 20℃).

Wire drawing process: A multi-pass wire drawing machine is used to draw copper rods into single wires of the target diameter. The temperature of the wire drawing die (≤40℃) and the concentration of the lubricant (emulsion concentration 5% to 8%) need to be controlled to prevent scratches or oxidation on the surface of the conductor.

Annealing treatment: Continuous annealing is carried out on copper single wires (temperature 300-400℃, time 10-15 seconds) to enhance flexibility (elongation ≥30%) and prevent cracking during subsequent processing.

2. Preparation of insulating materials

Particle screening: Select insulating materials (such as PVC, XLPE, silicone rubber) based on the temperature resistance grade of the cable, check the uniformity of the particles, and remove impurities or agglomerated particles.

Crosslinking treatment (for XLPE) : Through chemical crosslinking (adding DCP crosslinking agent) or physical crosslinking (electron irradiation), the molecular chains form a network structure, enhancing heat resistance (increasing the long-term working temperature from 70 ° C to over 90 ° C).

Ii. Conductor lamination process

1. Stranding and cabling

Twisted structure design: Determine the number of cores and their arrangement based on the cable specifications (such as 2-core twisted pair, multi-core layered twisted pair), and control the twisted pitch (generally 15 to 25 times the diameter of the conductor) to ensure that the wire cores are compact and round.

Tension control: A constant tension wire release device (tension fluctuation ≤5%) is adopted to prevent the conductor from stretching, deforming or loosening, which may affect electrical performance (such as impedance stability).

2. Filling and wrapping

Filling material laying: Fill rock wool, hemp rope or special filling strips in the twisting gap to improve the roundness and mechanical buffering capacity of the cable (filling rate ≥90%).

Wrapping layer processing: Use polyester tape or non-woven fabric for wrapping (overlap rate ≥15%), fix the filling material and provide a smooth base for the shielding layer. The wrapping speed should be matched with the cabling speed (error ≤±2%).

Iii. Insulation Extrusion process

1. Extrusion molding

Equipment parameter control: The temperature of the extruder is set in sections (such as 140~160℃ in the feeding section, 170~190℃ in the plasticizing section, and 180~200℃ in the die section) to ensure that the insulating material is fully plasticized and avoid the formation of bubbles or particles.

Thickness and eccentricity control: The thickness of the insulation layer (tolerance ≤±0.05mm) is monitored in real time by a laser diameter gauge. The traction speed (10-30m/min) and the screw speed (50-100 RPM) are adjusted to control the eccentricity < 10%.

2. Crosslinking and cooling

XLPE insulation cross-linking: Warm water cross-linking (temperature 90~95℃, time 12~24 hours) or steam cross-linking is adopted to ensure complete cross-linking of the insulation material (cross-linking degree ≥80%), thereby enhancing weather resistance.

Cooling and setting: The insulation layer is rapidly cooled through a cold water tank (water temperature ≤25℃) to prevent surface wrinkling or residual internal stress. After cooling, the insulation resistance (≥1000MΩ · km) needs to be tested.

Iv. Shielding Layer Processing Technology

Selection of shielding structure

Copper mesh weaving: High-speed weaving machines (with a rotational speed of 800 to 1200 revolutions per minute) are used, the copper wire diameter is 0.1 to 0.2mm, the weaving coverage rate is ≥85%, the lap rate is ≥10%, and the anti-electromagnetic interference capability is ensured (shielding attenuation ≥60dB).

Aluminum foil winding: The thickness of the aluminum foil is ≥0.1mm, the overlapping rate of the winding is ≥20%, and it is adhered to the copper braided grounding wire (cross-sectional area ≥0.5mm²) to ensure the continuity of the shielding layer grounding.

2. Key points of the process

During the weaving process, the tension of the copper wire (5-10N) is monitored in real time to prevent wire breakage or loosening. When winding aluminum foil, control the winding tension (10 to 15N) to prevent wrinkles.

V. Sheath Extrusion Process

1. Extrusion of sheath material

Material temperature control: The extrusion temperature of PVC sheath material is 160~180℃. For silicone rubber sheath, it needs to be combined with the vulcanization process (such as peroxide vulcanization temperature 180~200℃) to ensure that the surface of the protective sheath is smooth and free of bubbles.

Thickness and mechanical properties: The thickness of the sheath is set according to the cable usage environment (for example, the thickness of the outdoor cable sheath ≥1.5mm). After extrusion, the tensile strength (PVC≥15N/mm², silicone rubber ≥6N/mm²) and elongation at break (≥150%) are tested.

2. Printing and logos

The cable model, specification, factory name and execution standard (such as GB/T 9330) are continuously printed on the surface of the sheath using an ink printing machine. The clarity of the printed characters should be distinguishable under a 10x magnifying glass and be resistant to rubbing (not fading after being wiped 50 times with alcohol).

Vi. Cabling and Structural Integration

Multi-core cable cabling

Arrange the insulated wire cores as designed (such as stranded type or unit type), and adopt a fixed structure with tape wrapping (overlap rate ≥15%). The cable pitch should be 12 to 20 times the cable diameter to ensure the roundness of the cable core (ellipticity < 10%).

For highly flexible cables (such as those used in drag chains), an aramid fiber reinforcing layer (with a tensile strength of ≥2800MPa) needs to be added to enhance the bending resistance (with a minimum bending radius of ≤6D).

2. Special process treatment

Oil-resistant sheath treatment: Add oil-resistant additives (such as chlorinated paraffin) to the sheath material and test the resistance to mineral oil (volume change rate ≤±10% after 24 hours at 100℃).

Flame-retardant structure design: Flame retardants such as aluminium hydroxide are added to the sheath or insulating material, and pass the bundle combustion test (GB/T 18380.33, flame temperature 750℃, combustion time 40 minutes, carbonization height ≤2.5m).

Vii. Inspection and Quality Control

1. Electrical performance testing

Withstand voltage test: Apply 1500V industrial frequency voltage (rated voltage 0.6/1kV) to the finished cable for 1 minute without breakdown, and the partial discharge is ≤5pC.

Insulation resistance test: Measured with a 500V megohmmeter, the insulation resistance should be ≥100MΩ · km (at 20℃), and the on-resistance of the shielding layer should be ≤0.5Ω/km.

2. Mechanical and environmental performance testing

Bending test: Bend the cable 180° around a cylinder with a diameter of 10D. Repeat this process five times and check that there are no cracks in the insulation layer and no breaks in the shielding layer.

Aging test: Aging in a 70℃ oven for 168 hours. After aging, the retention rate of tensile strength of insulation/sheath is ≥80%, and the retention rate of elongation at break is ≥70%.

3. Other specialized tests

Conduct weather resistance tests on outdoor cables (with no cracking in the sheath after 500 hours of UV exposure); Salt spray resistance tests were conducted on Marine cables (35℃, 5% salt water spray, 48 hours without corrosion).

Viii. Winding and Packaging

1. Roll up the finished products

Use an automatic winding machine to neatly wind the cables onto cable reels (reel diameter ≥20D), with uniform winding tension (10~15N) to prevent excessive cable stretching (elongation rate ≤1%).

The edge of the cable reel is marked with warning signs such as "Prevent squeezing" and "Do Not Roll", and the production batch, length and inspection report number are recorded.

2. Packaging and Protection

The exposed cable ends are sealed with heat shrink caps to prevent moisture from entering. The outer layer of the cable reel is wrapped with waterproof plastic sheet and fixed with steel straps to adapt to the transportation environment (if it is transported by sea, moisture-proof treatment is required).

Comparison table of key process parameters

Ordinary control cables, high-flexibility drag chain cables, and high-temperature resistant cables (180℃) in the process link

Conductor twisting pitch: 15 to 25 times the conductor diameter; 8 to 12 times the conductor diameter (more compact); 12 to 18 times the conductor diameter (to prevent high-temperature relaxation)

Insulating materials: PVC (temperature resistance 70℃), PUR (temperature resistance -40 ℃ to 80℃), silicone rubber (temperature resistance -60 ℃ to 180℃)

Shielding coverage rate ≥80% ≥90% (Double-layer shielding: aluminum foil + copper mesh) ≥85% (tin-plated copper mesh)

Sheath thickness: 0.8-1.2mm, 1.0-1.5mm (wear-resistant PUR), 1.2-1.8mm (silicone rubber + glass fiber)

Bending radius ≥6D ≥4D (dynamic bending ≥1 million times) ≥8D (maintaining flexibility at high temperatures)

Process optimization direction

Intelligent production: Introducing Industry 4.0 technology, parameters such as the temperature and traction speed of the extruder are controlled by PLC (accuracy ±1%), and an AI visual inspection system is used to identify insulation layer defects (such as bubbles and scratches) in real time.

Green process: Halogen-free and low-smoke insulating materials (halogen content < 50ppm) are adopted to reduce the release of toxic gases during combustion and meet environmental protection standards (such as IEC 61034).

High-precision shielding: Utilizing a CNC weaving machine (positioning accuracy ±0.1mm), the shielding layer is evenly covered, enhancing the high-frequency anti-interference capability (shielding attenuation ≥80dB at 100MHz).

Summary

The production process of control cables takes "stable electrical performance, reliable mechanical structure and strong environmental adaptability" as its core goals. Through precise control in multiple links such as conductor processing, insulation extrusion, shielding and sheath forming, combined with full-process inspection, product quality is ensured. Different application scenarios (such as industrial control, ships, and new energy) have differentiated requirements for process parameters. It is necessary to optimize the stranded structure, material selection, and testing standards based on specific needs to maximize the performance of the cable.