The primary purpose of this stage is to reduce the metal wire diameter as required. Imported copper (Cu) or aluminum (Al) materials, typically with an initial diameter of 9.5mm (f9.5), are drawn into various sizes such as f4.0, f3.6, f2.8, f0.18… The machine contains a roller system that draws and pulls metal wire through multiple steel alloy dies of progressively smaller sizes. A hydraulic oil pumping system helps reduce friction, protect the dies, and prevent metal wire oxidation.

Typically, after drawing, the wire undergoes heat annealing to restore its flexibility and malleability. However, Ngoc Lan Cable’s factory features modern machinery that combines continuous drawing and annealing, making this stage a 2-in-1 process.

Depending on specifications, requirements, and applicable standards, metal conductors undergo different stranding methods: bunched stranding, concentric stranding, or compact concentric stranding. Common electrical wires and power cables typically use concentric stranding (or compact stranding when required) in configurations of 7, 19, 37, or 61 strands.

For producing 7-strand wire, the stranding machine has a rotating shaft with 1 central bin and 6 rotating peripheral bins to create concentrically stranded wire. If compacting is required, the final twist must pass through a die system that compresses the copper strands together, minimizing internal void spaces.

Depending on the application and applicable standards, wires and cables are insulated with different materials and colors. The voltage rating determines the insulation material, commonly XLPE, PVC, or HDPE. Insulation colors typically help electrical contractors distinguish between phases to avoid confusion during installation.

Some twisted cables receive ribbed insulation (LV-ABC, MV-ABC) or are marked with identification numbers for multi-core cables (Multiplex, control cables).

Power cables typically feature 2, 3, 4, 5… up to over 51 conducting cores. Therefore, core twisting is an essential process in Ngoc Lan Cable’s manufacturing plant. For large-core cables, the core laying machine (group laying) includes additional filling materials to achieve better roundness. Common fillers include PP or PVC synthetic fibers.

To enhance protection, wires & cables often receive 1-2 layers of metal armor, which can be copper, aluminum, steel, etc. Metal armor is produced in various forms such as tape armor, wire armor, or mesh armor. This process occurs simultaneously during cable core twisting.

After core twisting and armoring, cables undergo the final stage of jacket coating and surface marking. The coating machine extrudes plastic around the twisted cores, creating the finished conductor.

Jacket materials are similar to insulation materials, with additional options like FR-PVC for flame-retardant properties. Jacket colors and cable markings are produced according to customer requirements.