Wanma Macromolecule XLPE BD-PE is fed from sealed aluminum-foil-lined bags into the hopper of a single-screw extrusion line producing single-core low-voltage power cable rated 0.6/1 kV. The insulation is applied directly onto annealed copper conductors from 1.5 mm² to 10 mm². The extruder uses a 25:1 L/D barrier screw with a 3.0:1 compression ratio. Barrel temperatures are set from 135°C at the feed throat to 170°C in the metering section. Head pressure is held between 120 bar and 160 bar. Melt temperature at the die is not permitted to exceed 180°C. A screen pack of 60/80/100 mesh removes contamination above 0.25 mm. The copper conductor is preheated to 80-100°C before entering the crosshead. Insulation wall thickness is 0.7 mm for 1.5 mm² conductor and increases for larger cross-sections. The extrudate passes through a cooling trough and then enters a wet storage chamber at 85-95°C. Silanol condensation continues for 4-8 h depending on wall thickness. Hot set testing is performed per IEC 60811-507 at 200°C under 0.2 MPa for 15 min. The acceptance threshold is ≤175% elongation under load and ≤15% permanent set after cooling. Terminal finished products include fixed-installation low-voltage power cable for building distribution, panel feeder conductors, and internal wiring in dry locations with continuous conductor temperature 90°C.

What Constrains Extrusion Speed in Photovoltaic DC Cable Insulation?

In 1500 V DC photovoltaic cable production, the limiting factor is not the extruder throughput but the downstream crosslink bath length and the scorch margin of the compound. Tinned flexible copper conductors from 1.5 mm² to 35 mm² are insulated to 0.5-0.7 mm wall thickness. The compound is gravimetrically blended with catalyst masterbatch at a 95:5 mass ratio. Feeder precision is controlled to ±0.5 wt%. A loss-in-weight dosing unit is required. Barrel temperatures are set 10-15°C lower than building-wire profiles. The feed zone is held at 130°C, the metering zone at 165°C, and the head at 170°C. Melt temperature is measured by infrared sensor and must not exceed 178°C. Premature crosslinking produces visible scorch particles that pass through the 0.25 mm screen pack and cause spark-test faults. The extruder is a 30:1 L/D single-screw machine with a double-flighted barrier mixing section. Screw speed is typically limited to 45-70 rpm depending on conductor cross-section. Line speed is capped by crosslink bath residence time. A water bath at 90°C requires 6-8 h for full crosslink at 0.6 mm wall. Steam chambers at 95% relative humidity reduce this to 4-5 h. Gel content is checked by xylene extraction per ASTM D2765-16 Method A, with a minimum of 65% for release. Finished cable is tested per EN 50618 and IEC 62930. End-use products include H1Z2Z2-K photovoltaic cables with silane-crosslinked insulation and a separate low-smoke zero-halogen sheath. Do not combine the compound with amine-based antistatic masterbatches, because amine groups accelerate premature silanol condensation and produce surface pitting.

Automotive battery cable insulation crosses the 125°C thermal class boundary only after complete silanol condensation

Battery cable insulation for low-voltage automotive applications is extruded on flexible copper conductors with wall thickness from 0.48 mm to 1.00 mm. The conductor is pre-dried to remove surface moisture. The compound is dried at 70°C for 2 h in a desiccant dryer with dew point not higher than -40°C only when bags have been opened for more than 30 min at relative humidity above 60%. The extrusion line uses a 20:1 L/D single-screw extruder with a polyethylene-type screw. Temperature zones range from 140°C to 175°C. Head pressure is kept below 140 bar. The conductor is preheated to 90°C before the crosshead. Crosslinking is completed in a 90°C water bath or a 90% RH steam chamber. For 0.75 mm wall, crosslink time is 5-7 h. Partially cured insulation fails hot set testing and also shows reduced abrasion resistance. The material meets ISO 6722-1 class C long-term heat ageing at 125°C for 3000 h when processed within these boundaries. Terminal products include engine compartment battery ground cables, starter cable interconnects, and charge accessory leads rated for 125°C continuous service after full crosslinking.

Class F motor lead wire is insulated directly with a single layer of silane-crosslinked polyethylene on flexible copper. The application requires a 600 V rating and repeated bending during motor termination. Wall thickness is set at 0.4-0.5 mm for AWG 18-14 conductors. The line uses a 25:1 single-screw extruder with a vacuum hopper and a pressure-relief crosshead. Melt temperature is limited to 170°C to avoid scorch. Crosslinking is completed in low-pressure steam at 85°C for 3-5 h. The resulting insulation is tested for dielectric strength per IEC 60243-1, with a typical acceptance value of ≥20 kV/mm. Flame testing and ageing are conducted to UL 1581 reference methods. Terminal products include motor lead wires for submersible pumps and industrial fan motors. The material is not recommended where the lead wire is submerged in hot transformer oil above 80°C, because oil absorption reduces long-term mechanical integrity.

Control and instrumentation cable insulation under IEC 60092-350

Multi-core control cable insulation for marine and industrial automation is extruded on stranded tinned copper conductors. Conductor sizes range from 0.75 mm² to 2.5 mm². Insulation wall is 0.6 mm for 250 V circuits. The compound is processed at 145-170°C barrel temperature. A 24:1 L/D single-screw extruder is used with a pressure-relief head. Crosslinking at 90°C in a water bath for 5-6 h is followed by 24 h ambient conditioning. Dielectric constant is 2.3 at 1 MHz. Dissipation factor is below 0.0004 at 1 MHz. These values keep capacitance low in twisted pairs. Insulation resistance is measured per IEC 60093 with a minimum of 1×10¹⁵ Ω·cm. The finished cables are tested for cold bend at -40°C. Terminal products include shipboard control cables, machinery control cables, and fieldbus trunk cables where the sheath is a separate low-smoke zero-halogen compound.

When EV charging cable insulation requires wall-thickness variation below 0.05 mm

EV charging cable insulation is produced on high-flex copper conductors with cross-sections from 2.5 mm² to 16 mm². The wall thickness is specified at 0.8 mm for 450/750 V rated cores. Wall-thickness variation cannot exceed 0.05 mm along the cable core. The extrusion line uses a 30:1 L/D single-screw extruder with a crosshead designed for concentricity control. A laser diameter gauge and an X-ray wall-thickness scanner are placed 1.5 m after the die. The screw speed is held between 35 rpm and 55 rpm. Melt temperature is 165-175°C. The conductor is preheated to 95°C. Crosslinking takes place in a 90°C water bath with a minimum residence time of 6 h for 0.8 mm insulation. Uncrosslinked material is detected by hot set sampling every 4000 m of insulated conductor. The cable must meet EN 50620, IEC 62893, and GB/T 33594 ageing profiles. Terminal products include flexible EV AC charging cables and mode 3 charging leads. The material is not used as the outer sheath; a separate halogen-free sheath compound is extruded over the insulated cores.