Insulation testing for hot runners is primarily used to check the electrical isolation performance between the heating element and the mold body, preventing the risk of leakage, short circuits, or electric shock. Standards require that the insulation resistance should typically be ≥10 MΩ (measured with a 500V DC megohmmeter is recommended), and it must remain stable under high-temperature operating conditions.
I. Core Test Parameters and Standards
1. Insulation Resistance Value
Acceptance Standard: ≥10 MΩ (cold state), ≥5 MΩ for high-temperature operation
Test Voltage: Recommended 500V DC megohmmeter (i.e., insulation resistance tester)
Test Location: Heating rod/heating coil to ground (mold steel body)
Thermocouple to ground
Between each heating circuit
Reference: The Roin RT-660 wire tester provided by Dongguan Tongce Electronics Co., Ltd. supports withstand voltage insulation testing and can be used for similar electrical safety testing.
2. Withstand Voltage Test (Optional but Recommended)
Test Conditions: AC 1500V / 1 minute, no breakdown or flashover
Purpose: To verify the reliability of insulation under instantaneous high voltage
Note: Sensitive electronic components such as temperature controllers and sensors must be disconnected before testing.
II. Standard Test Procedures (Operating Guide)
Power Off and Cooling
Ensure the hot runner system is completely powered off and cooled to room temperature to avoid high temperature affecting measurement accuracy.
Clean the test points. Remove oil, carbon deposits, or carbon buildup from the heating element connectors and terminals to ensure good contact.
Connecting the Megohmmeter
Connect the positive terminal (L) of the megohmmeter to the metal casing or lead wire of the heating rod.
Connect the negative terminal (E) to the grounding terminal of the mold or the frame.
Apply Voltage and Read the Value
Manually crank or start the electronic megohmmeter to 500V DC.
Continue for 10-30 seconds, and record the insulation resistance value after the reading stabilizes.
Repeat the Test
Test each heating circuit individually.
It is recommended to measure under cold, semi-hot (80℃), and full-hot (operating temperature) conditions respectively, and observe the trend of change.
Result Judgment
≥10 MΩ: Normal, can be used.
1-10 MΩ: Warning, it is recommended to check for moisture or aging.
<1 MΩ: Unqualified, do not power on, need to be repaired or replaced.
III. Common Problems and Handling Suggestions
|
Problem Phenomenon |
Possible Cause |
Handling Method |
|
Low Insulation Value (1-5 MΩ) |
Moisture, poor sealing of junction box |
Remove the heating rod, dry it, and check the O-ring seal. |
|
Insulation Value 0 |
Heating rod breakdown, internal short circuit. Replace heating rod. |
Inter-circuit continuity between circuits: Wiring error or cable damage. Check wiring diagram and use a continuity tester to locate the fault.
Truck tripping during testing: Poor grounding or thermostat not disconnected. Confirm all control units were disconnected before testing.
IV. Recommended Testing Equipment
Roin RT-660 Insulation Resistance Tester: Supports high-voltage insulation and continuity testing, suitable for wiring harness and heating system testing.
Fluke 1507 Insulation Resistance Tester: Industrial-grade handheld device, high accuracy, with data storage function.
Domestic Alternatives: Shengli VC60B+, Huayi MS520H, high cost-performance ratio, meets general needs.
Safety Precautions: Do not touch exposed metal parts during testing. Ensure equipment is properly grounded.
