The specific steps for partially cutting and reconnecting the magnesium oxide insulation layer are as follows. This operation is only applicable when the terminals are slightly damp and the length of the heating tube allows for cutting:
1. Power Off and Disassembly
Completely disconnect the power supply to the equipment, ensuring no residual voltage.
After the heater has completely cooled, remove the failed component from the hot runner system.
Clean the surface of oil and carbon deposits to facilitate subsequent operations.
2. Determine the Moisture Range and Mark the Cutting Location
Use a megohmmeter for preliminary testing to determine the area of abnormal insulation resistance.
Observe the terminals for water stains, rust, or crystals (such as white powder, which is Mg(OH)₂). Mark a safe cutting length extending at least 50mm inward from the visible moisture point with a marker.
3. Trim the Damaged Section
Use a specialized cutting tool (such as a small grinder or pipe cutters) to neatly cut along the marked line;
The cut must be smooth and burr-free to avoid damaging the internal heating wire and magnesium oxide filler layer;
Do not forcibly bend or strike to prevent loosening of the internal structure.
4. Re-strip and Crim the Leads
Strip approximately 10–15 mm of the inner insulation layer to expose the metal core wire;
Lightly sand the core wire until shiny to remove the oxide layer;
After applying conductive paste, insert the core wire into the new terminal and crimp it tightly with hydraulic crimping pliers, ensuring a contact resistance ≤ 0.03Ω.
5. Multi-layer Sealing Protection
Wrap Waterproof Tape: Evenly wrap 2-3 turns of self-fusing waterproof tape around the crimped joint and surrounding area;
Heat Shrink Tubing Sealing: Insert high-temperature resistant heat shrink tubing (diameter 2-3 cm larger than the crimped joint), and use a heat gun to evenly shrink it from the center outwards;
Optional Enhanced Sealing: Apply an additional layer of silicone rubber sealant over the heat shrink tubing to improve the moisture resistance.
After sealing, allow it to stand for at least 2 hours to allow the sealant to fully cure.
6. Insulation Performance Test
Use a 2500V megohmmeter to measure the insulation resistance between the new connector and the metal casing;
≥100 MΩ is acceptable; values below this require reprocessing;
If necessary, perform a withstand voltage test (AC 2000V, no breakdown for 1 minute).
7. Installation and Power-on Verification
Reinstall the repaired heater, ensuring the heating area is fully immersed;
Preheat at 50% power for 30 minutes, observing for any abnormal temperature rise or leakage alarms;
Gradually increase to rated power and confirm stable operation.
Note: This method is for emergency use only. It is recommended to replace the entire heating element in the future to ensure long-term reliability.
