The key indicator for determining if a hot runner system has good insulation is an insulation resistance >10MΩ under high-temperature operating conditions. This should be combined with visual inspection, electrical testing, and a comprehensive evaluation of historical data to ensure the system's safe and stable operation.
1. Core Judgment Criterion: Insulation Resistance Value
Ideal State: Under high-temperature operation (150℃~400℃), the insulation resistance should be >50MΩ;
Minimum Acceptance: Not less than 10MΩ. A value below this indicates a risk of leakage;
Cold State Reference Value: At room temperature, the insulation resistance should be >100MΩ, serving as a preliminary judgment basis before commissioning.
Note: For every 10℃ increase in temperature, the insulation material resistance decreases by approximately half. The actual insulation performance needs to be dynamically evaluated in conjunction with temperature.
2. Judgment Steps and Key Operating Points
|
Steps |
Operating Instructions |
|
Power Off and Cooling |
Turn off the heating power and wait for the system to cool to <80℃, ensuring safe operation. |
|
Visual Inspection |
Check the junction box, plug, and heating rod ports for signs of burning, carbonization, or moisture condensation. |
|
Cleaning |
Wipe the terminals with anhydrous alcohol to remove oxide layers and dirt, avoiding poor contact that could interfere with the test. |
|
Applying Test Voltage |
Use a 500VDC megohmmeter. Connect the L terminal to the heating circuit and the E terminal to the casing or ground wire. |
|
Reading Stable Value |
Maintain the test for 1 minute and record the final stable resistance value. |
|
Data Comparison |
Compare with historical records. If the sudden drop exceeds 50%, internal aging or moisture should be investigated. |
Risk Warning: If the measured resistance is <1MΩ, it indicates a serious insulation failure. Do not power on; disassembly and repair are necessary.
3. Auxiliary Judgment Methods
Power-on Operation Monitoring: Observe for abnormal tripping, large current fluctuations, and inaccurate temperature control; Use an infrared thermal imager to detect localized overheating points, which may be precursors to leakage.
Environmental Factors: High temperature and humidity environments (such as Wuhan in summer) can easily lead to insulation degradation; it is recommended to increase the testing frequency to once every two weeks; Insulation testing must be completed before restarting after a long-term shutdown.
