I. Dynamic Insulation Resistance Method
Determination Procedure: Every hour during baking, use a 500V digital megohmmeter to re-measure the insulation resistance between the heating element, sensor core wire, and housing of the hot runner channel.
Moisture Absorption Characteristics: Initially, the insulation resistance is <5MΩ, and as the baking temperature increases, the insulation resistance shows a continuous and steady upward trend, indicating that moisture exists inside the hot runner channel and is gradually being dried.
Drying Completion Determination: After two consecutive tests with a 1-hour interval, if the insulation resistance is ≥20MΩ and the value no longer increases significantly, it indicates that the moisture has been completely removed and the hot runner channel is no longer damp.
II. Appearance and Physical Characteristics Method
Determination Procedure: During the baking process, periodically observe the changes in the condition of the hot runner sealing surface, junction box gaps, and exposed metal surfaces.
Moisture Absorption Characteristics: In the initial stage of baking, a fine water mist quickly appears on the surface of the hot runner channel, and obvious hot air escapes from the junction box gaps, indicating that a large amount of moisture has been absorbed internally, indicating a significant moisture absorption state.
Drying Completion Criteria: After 2 hours of continuous baking, surface water vapor completely disappears, no more hot air escapes, and there are no condensation marks on the metal surface, indicating that surface moisture has been completely removed.
III. Heating Lag Characteristic Criteria
Criteria Operation: Record the heating rate of the hot runner during baking and compare it with the standard heating curve of a similar model of drying hot runner.
Moisture Absorption Criteria: After the hot runner reaches 100℃, it remains at a low temperature for an extended period and cannot continue to rise. A large amount of heat is vaporized and carried away by internal moisture, indicating the presence of a large amount of free moisture, indicating a severely damp state.
Drying Completion Criteria: After exceeding 100℃, the heating rate of the hot runner returns to the standard level of a similar model of drying hot runner, with no obvious temperature plateau, indicating that internal moisture has been completely vaporized and removed.
IV. Special Scenario Auxiliary Criteria:
Slightly Moist Hot Runner: Only the insulation resistance is slightly below 5MΩ, there is no obvious water vapor, no heating stagnation, and dehumidification can be completed with just 8 hours of standard baking. Severely Moist Hot Runner: Meeting the following three characteristics simultaneously-insulation resistance <1MΩ, significant surface condensation, and prolonged temperature hold at 100℃-the total baking time must be extended to 20-24 hours to prevent residual moisture from causing insulation breakdown in subsequent heaters.
No Moisture Criterion: If the insulation resistance remains ≥20MΩ throughout the baking process, with no water vapor overflow and a completely normal temperature rise curve, the hot runner is not moist, and baking can be directly terminated to proceed to the installation stage.
