For drying a hot runner system that has been exposed to moisture, the most suitable method is low-temperature heat-soaking. This involves-once the insulation resistance is confirmed to be ≥100 kΩ-setting the temperature controller to 80–100°C and running the system for 1–2 hours. By leveraging the system's inherent advantages of uniform heating and stable heat conduction, this process safely and effectively expels internal moisture.
1. Why is low-temperature heat-soaking the most suitable method?
Uniform Heating: Heat is conducted outward from within the heating elements, effectively penetrating sealed cavities-such as the manifold plate and nozzles-to drive out moisture trapped in microscopic pores.
Avoidance of Thermal Shock: A gradual temperature rise (recommended rate: 10–20°C/min) prevents deformation of sealing rings or material cracking that could result from excessive temperature differentials.
Protection of Insulation Materials: By keeping the temperature within 100°C-well below the tolerance limit of the silicone insulation layer (≥300°C)-the risk of carbonization or material aging is eliminated.
Operational Convenience: No additional equipment is required; the process can be executed directly using the existing temperature control system, making it ideal for rapid on-site response.
Applicable Scenarios: Mild to moderate moisture exposure where the insulation resistance falls within the range of 100 kΩ to 1 MΩ, provided there is no visible standing water and the connectors are free from severe contamination.
2. Comparison of Other Drying Methods and Their Applicable Conditions
|
Drying Method |
Applicable Conditions |
Advantages |
Risks and Limitations |
|
Low-Temperature Heat Preservation Drying |
Insulation ≥ 100 kΩ; unit is slightly damp overall |
Uniform heating; safe and reliable; requires no external equipment |
Unsuitable for cases of severe water ingress or insulation < 100 kΩ |
|
External Hot Air Drying |
Localized dampness (e.g., junction boxes, connectors) |
Allows for precise treatment of external components; rapid drying |
Limited to surface drying; difficult to penetrate internal structures; improper temperature control may damage materials |
|
Natural Ventilation + Desiccants |
Ample downtime available; minor dampness |
No risk of electrical hazards; suitable for long-term moisture prevention during storage |
Low efficiency; typically requires 24–48 hours; cannot meet urgent production demands |
Industry Best Practice Recommendation: Prioritize Low-Temperature Heat Preservation Drying as the primary solution, supplemented by External Hot Air drying for exposed components (such as connectors), to establish a comprehensive, synergistic strategy for moisture removal-addressing both internal and external areas.
3. Key Points for Implementation
Mandatory Pre-Inspection: Use a 500V DC megohmmeter to verify that the insulation resistance is ≥ 100 kΩ; otherwise, energizing the equipment is strictly prohibited.
Prohibition on Full-Power Startup: Never set the temperature directly to the molding process setpoint (e.g., above 200°C) immediately, to prevent localized arcing or short circuits.
Segmented Monitoring: Power off the equipment every 30 minutes to re-measure the insulation resistance value and observe whether it is steadily increasing.
Post-Cooling Verification: Upon completion of the drying process, allow the system to cool down to room temperature before measuring the insulation resistance again; ensure that all channels register > 1 MΩ before placing the equipment back into operation.
