The core method for determining whether a hot runner system has been compromised by moisture involves a combination of insulation resistance testing, visual inspection, and environmental analysis. If a megohmmeter measures an insulation resistance value between 100 kΩ and 1 MΩ (with no obvious physical damage), or if condensation, blackened metal components, or rust are observed inside connectors or terminal boxes, the system can be deemed to have suffered moisture damage.
1. Insulation Resistance Testing (Key Indicator)
Typical Manifestations:
When measured in a cold state, the insulation resistance value falls between 100 kΩ and 1 MΩ; however, the resistance value recovers somewhat after the system has been heated and operated for a period.
A drop in resistance values is observed simultaneously across multiple points, yet there are no signs of localized burnout or carbonization.
Testing Recommendations:
Use a 500V DC megohmmeter to test the cables, connectors, and heating elements in sections.
In the early stages of moisture damage, the issue often manifests as a "soft fault"-characterized by unstable resistance values that are highly susceptible to fluctuations in ambient humidity.
2. Visual and Tactile Inspection (Auxiliary Assessment)
Connectors and Terminal Boxes:
Upon opening the connectors or terminal boxes, check for the presence of water droplets, mist/fogging, metal oxidation, or white powdery deposits.
If the O-ring seals appear aged or deformed, and the interior is damp, this indicates a seal failure that has allowed moisture to infiltrate the system.
Mold Storage Environment:
Check whether the mold is stored in an area with poor ventilation, high humidity, or significant temperature fluctuations between day and night, as these conditions are prone to generating condensation.
For molds that have been shut down and left unused for extended periods, the appearance of slight rust or traces of condensation around the heating elements is a classic sign of moisture damage.
3. Analysis of Environmental and Operational Characteristic
Correlation with High-Humidity Environments:
Faults occur most frequently during the rainy season, in coastal regions, or in workshops lacking dehumidification equipment.
If the machinery is powered down over weekends or during the night, the alternating cycles of heating and cooling can easily cause condensation to form internally, thereby exacerbating the risk of moisture damage. The "Self-Recovery" Phenomenon Upon Heating:
After the system is powered on and preheated for 30 minutes, the insulation resistance rises significantly. This indicates that moisture has evaporated-a typical characteristic of moisture ingress.
Note: Moisture ingress often serves as a "prelude" to insulation degradation. Even if the current readings have not yet reached the fault threshold, immediate measures-such as drying, cleaning, and reinforcing seals-should be implemented to prevent the condition from escalating into permanent damage.
