According to IEC 60204-1 and GB/T 25296-2022 standards, the core criterion for determining if the insulation performance of hot runners is qualified is: under a 500 V DC test voltage, the insulation resistance between the live parts and the protective connection circuit (mold body) should be ≥1 MΩ. Meanwhile, based on industry practice, the injection molding industry generally adopts a stricter internal control standard-≥10 MΩ in cold state and ≥5 MΩ in hot state as the qualification threshold.
I. Direct Judgment Requirements in the Standard
1. IEC 60204-1:2018 (General Standard for Electrical Safety of Machinery)
Test Item: Insulation Resistance Test (Clause 18.3)
Test Conditions:
Apply 500 V DC voltage
Measure the resistance between the live part (e.g., heating rod lead) and the accessible metal part (mold body)
Pass/Fail Judgment:
Insulation resistance ≥ 1 MΩ
No breakdown, no flashover (applicable to withstand voltage test)
Additional Requirements: Must pass the protective connection circuit continuity test (grounding resistance ≤ 0.1 Ω)
Recommended withstand voltage test: AC 1500 V / 1 min, no breakdown
Note: IEC 60204-1 is an internationally recognized standard for electrical safety of machinery. All exported equipment or injection molding machines with CE certification must meet this standard.
2. GB/T 25296-2022 (General Test Guidelines for Electrical Equipment Safety in China)
Scope of Application: Electrical equipment with a rated voltage ≤1000 V, fully covering hot runner systems.
Test Method: Insulation resistance is measured using DC voltage (500 V DC recommended).
Ambient temperature and humidity during testing must be recorded.
Pass/Fail Criteria: No specific numerical threshold is given, but "insulation performance testing" is explicitly listed as one of the six major categories of safety inspections.
In actual implementation, the judgment should be made in accordance with IEC 60204-1 or GB 19517 mandatory standards.
Test Types:
Type Test: New product design verification
Factory Test: Must pass before each system leaves the factory.
Note: GB/T 25296-2022 is a recommended national standard, but it differs from GB 19517 "National Electrical Equipment Safety Technical Specification". Used in conjunction with the latter, which is a mandatory standard and constitutes the legal basis for domestic compliance.
II. Industry-Specific Compliance Standards (Higher Than Basic Requirements)
Although the minimum standard requirement is ≥1 MΩ, hot runners operate in high-temperature, oil-contaminated, and vibration-prone environments, posing a high risk of insulation aging. Therefore, the industry generally adopts stricter internal control thresholds:
|
Status |
Compliance Standard |
Basis and Explanation |
|
Cold State (Room Temperature) |
≥10 MΩ |
Recommended value in most manufacturers' (e.g., Yudo, Husky) maintenance manuals, reflecting initial insulation quality. |
|
Hot State (Operating Temperature) |
≥5 MΩ |
Referencing IEC 60335-1 requirements for hot-state insulation in household appliances, as a safety redundancy. |
|
Trend Change |
Continuous decrease in value triggers an early warning |
Even if not below the threshold, if it changes from 30 MΩ to 8 MΩ, maintenance should be scheduled. |
Key Reminder: Single pass rate ≠ long-term safety. It is recommended to establish an insulation resistance history file for each hot runner system to achieve trend-based management.
III. Complete Judgment Process (Combining Standards and Practical Operation)
Power Off and Cool Down: Shut down the system for at least 4 hours to ensure it cools to room temperature and avoids high temperatures affecting measurement accuracy (complies with GB/T 25296-2022 environmental adaptability requirements).
Disconnect Sensitive Electronic Components: Disconnect the temperature controller and PLC wiring to prevent high-voltage backflow from damaging the control module (mandatory requirement of IEC 60204-1 §10.3).
Clean Test Points: Wipe the heating rod socket and terminals with anhydrous alcohol to avoid surface contamination leading to misjudgment (refer to IEC 62631-3-1 surface resistance control).
Connect Megohmmeter for Testing:
L terminal → Heating rod metal casing or lead wire
E terminal → Mold body (reliably grounded)
Apply 500 V DC, maintain for 10–30 seconds, and read the stable value.
Multi-Site Testing:
Test each heating zone individually. Thermocouple insulation to ground. Insulation between circuits.
Result Judgment:
≥10 MΩ: Meets industry high reliability standards and is ready for use.
1～10 MΩ: Meets IEC minimum requirements, but moisture and contamination must be checked; a warning is recommended.
<1 MΩ: Unqualified; do not power on; must be repaired or replaced.
Records and Traceability
Record test time, location, measured values, and environmental conditions. Digital archiving facilitates auditing and trend analysis (complies with the spirit of continuous monitoring in GB/T 25296-2022, Clause 7.4).
Safety Reminder: Wear high-temperature resistant gloves and safety glasses throughout the testing process. Do not touch exposed metal parts. Ensure reliable grounding.
