The core principle for quickly addressing a hot runner system exposed to moisture is as follows: immediately cut off power, perform segmented testing of insulation resistance, clean and dry the affected areas, and only gradually resume operation after confirming that the insulation value has recovered to above 1 MΩ.
Step 1: Immediate Shutdown and Power Disconnection
Turn off the power to the temperature control unit and disconnect the hot runner system from the control cabinet.
Place a "Do Not Energize" warning sign on the power distribution cabinet to prevent accidental operation that could lead to short circuits or electric shock.
Step 2: Preliminary Assessment of the Affected Area
Check if multiple heating zones are triggering alarms simultaneously (e.g., for leakage current or overcurrent); this suggests that a shared path (such as the main power cable or junction box) has been exposed to water ingress or condensation.
Inspect the mold storage environment for any obvious signs of condensation, cooling water leaks, or high humidity.
Step 3: Segmented Measurement of Insulation Resistance
Use a 500V DC megohmmeter to perform the following tests:
First, measure the insulation resistance of the entire circuit to ground:
If > 1 MΩ: The system is generally normal; continue to monitor.
If < 1 MΩ: Moisture ingress or contamination is present; further troubleshooting is required.
Next, isolate and test each segment individually:
Cable Harness: Disconnect both ends and measure the insulation resistance between the conductors and the shielding layer.
Connectors: After cleaning, measure the resistance between the terminals and the connector housing.
Heating Element Body: Connect the "L" terminal to the electrode core and the "E" terminal to ground; measure the resistance to ground.
Note: Do not apply power directly to dry the system without first performing these diagnostic tests!
Step 4: Cleaning and Localized Treatment
Remove the connectors and thoroughly wipe the terminal surfaces with anhydrous alcohol to remove any water films, oil residues, or carbonized deposits.
Use dry compressed air or a low-temperature heat gun (≤ 80°C) to blow dry the junction boxes, plugs, sockets, and surrounding areas, taking care to avoid using excessive heat that could damage the insulation materials.
Step 5: Low-Power Drying (Proceed with Caution)
Condition: Proceed only if the measured insulation resistance is ≥ 100 kΩ.
Method:
Set the temperature controller to "Low-Temperature Hold Mode" (80–100°C) and maintain heating for 1–2 hours;
Alternatively, use external hot-air equipment to bake the mold's electrical cavities from the outside.
Monitoring: Re-measure the insulation resistance value every 30 minutes using a megohmmeter to observe whether it is steadily increasing.
Step 6: Pre-Operation Verification
After drying, allow the system to cool to room temperature, then measure the insulation resistance again to ensure that all channels read > 1 MΩ.
Reconnect the wiring and run the system under a no-load condition for 30 minutes; observe whether the temperature remains stable and check for any abnormal noises or signs of smoke.
Assign a dedicated personnel to stand by and monitor the first two molding cycles; proceed to normal production only after confirming that no anomalies are present.
Note: If the insulation resistance value remains below 100 kΩ after drying, it indicates that carbonization or permanent damage has likely occurred. In this case, the heating rods or cables must be replaced; do not attempt to force the system to start.
