When a hot runner system overheats, critical intervention must be completed within 90 seconds to prevent material degradation, equipment damage, and safety accidents. The following is a standardized emergency response procedure based on engineering practice and material properties, applicable to industrial injection molding production environments.
I. Immediately Cut Off the Heat Source – First Action, No Hesitation
Operation: Immediately press the E-Stop button on the temperature controller;
If there is no response, manually disconnect the heating circuit air switch (not just turn off the temperature controller interface);
Do not simply turn off the temperature controller power – the heating coil may still be energized and continue to generate heat.
Key Principle: Heat source disconnection must be physically isolated, not just software-based.
Basis: Both Husky and Mold-Masters require that "power disconnection takes precedence over any other operation."
II. Close All Needle Valves – Block Melt Flow to Prevent Drooling and Leakage
Operation: Manually trigger the close command for all hot runner needle valves (even if the system is powered off);
If it is a pneumatic needle valve, immediately shut off the air supply;
If it is an electric needle valve, confirm that the control signal has failed, and manually mechanically lock it (if applicable).
Purpose: To prevent high-temperature melt from continuously dripping from the gate without pressure control, avoiding mold contamination and slag buildup.
III. Maintain Cooling Circulation – Do Not Stop Water or Airflow
Operation:
Keep the cooling water system running (even if heating has been stopped);
Keep the hot runner cooling fan running continuously;
Do not immediately shut off the cooling pump or compressed air.
Principle: The hot runner metal (such as H13 steel) has a large heat capacity, and a large amount of residual heat remains even after heating is stopped. Continuous heat dissipation is necessary to prevent thermal stress cracking.
Data: Within 10 minutes after cooling stops, the hot runner temperature can still rise by 15–25°C, causing the sealing ring to melt.
IV. Activating Forced Ventilation – A Matter of Life and Death for Heat-Sensitive Materials
Material Overheating Gas Release Emergency Ventilation Requirements
POM Acetaldehyde (CH₃CHO) Immediately activate the local exhaust system, with a wind speed ≥2 m/s for at least 30 minutes; test the acetaldehyde concentration in the air (limit: 5 ppm)
PA6/PA66 Amines, Ammonia Activate full ventilation in the workshop to prevent ammonia accumulation and equipment corrosion.
PC, PLA No obvious toxic gases No forced ventilation required, but air circulation must still be maintained.
Safety Red Line: After POM overheats, do not open the mold or approach the gate area before ventilation. Acetaldehyde is flammable (explosion limits 4–11.8%).
V. Isolation and Protection – Personnel Safety Prioritized over Equipment Safety
Operation:
Evacuate non-essential personnel within 5 meters;
Operators must wear respirators (for POM), high-temperature resistant gloves, and face shields;
Establish a warning perimeter and prohibit unauthorized personnel from approaching the hot runner area.
Accident Case: In a medical injection molding plant, due to lack of ventilation, acetaldehyde gas accumulated and ignited upon contact with static sparks, causing a minor deflagration that resulted in minor injuries to two people.
VI. System Diagnostic Preparation – Data Acquisition Before Shutdown
After confirming that the temperature has stabilized (<150℃), perform the following:
Export historical temperature controller curves: Focus on recording the peak temperature, duration, and fluctuation frequency;
Take photos: Record scorch marks on the hot runner surface, gate residue, and the deformation status of the sealing ring;
Record abnormal phenomena: Whether there is stringing, unusual odor, abnormal noise, or material leakage.
Purpose: To provide a basis for subsequent fault analysis and avoid repeating mistakes.
VII. Shutdown and Maintenance – Unplanned shutdowns require thorough investigation.
Operating Procedure:
Wait until the temperature drops below 80℃, then turn off the main power supply;
Lock and tagged the unit (LOTO), and obtain a maintenance ticket;
Inspection Items:
Check for:
Thermocouple looseness or oxidation (replace if drift is ±0.5℃);
Heating coil resistance increase >10%;
Insulation resistance <50 MΩ;
Sealing ring cracks or hardening;
Carbon deposits or degradation residue in the flow channel.
Repair Principle: After any overheating event, the hot runner sealing ring and thermocouple must be replaced, even if there is no visible damage.
Emergency Handling Golden Rules:
Heat cut-off → Valve closure → Cold insulation → Ventilation → Protection → Recording → Maintenance. Missing any step may lead to secondary accidents or irreversible equipment damage.
Industry Consensus: 90% of hot runner failures stem from "failure to follow procedures after overheating," not from the overheating itself.
