I. Pre-Heating Preparation Optimization
Hot Runner Status Pre-confirmation: After drying and cooling, the insulation resistance of the entire channel is stable at ≥20MΩ. Residual old material in the runner has been completely replaced with special cleaning material, and there is no hidden moisture or dead-angle residue.
Temperature Control System Pre-calibration: Calibrate thermocouples channel by channel, controlling temperature deviation within ≤±1℃. Complete the self-tuning of PID parameters for each channel to match the thermal inertia characteristics of the current hot runner.
Hardware and Environmental Pre-check: Confirm that the heating coils and wiring terminals are not loose or oxidized, the power supply voltage is stable within ±5% of the rated value, and turn off the surrounding air coolers directly blowing on the hot runner to eliminate airflow interference sources.
II. Heating Curve Gradient Optimization
Low-Temperature Preheating Section: Heat from room temperature to 30℃ below the material's heat distortion temperature at a rate of ≤2℃/min, and hold for 30 minutes to avoid uneven local thermal stress caused by rapid heating.
Medium Temperature Transition Section: Heat to the lower limit of the material processing temperature range and hold for 20 minutes to ensure uniform temperature distribution throughout the flow channel plate and eliminate internal temperature differences.
Production Temperature Section: Gradually increase the temperature to the midpoint of the recommended processing temperature range for the material. Do not set the temperature directly to the upper limit. Hold for 15 minutes before feeding material.
III. Temperature Stability Optimization
Power Output Limitation: Limit the maximum output power of each heating channel to within 70% to avoid significant temperature fluctuations caused by full-power start-up and shutdown.
Zoned Staggered Heating: Large multi-cavity hot runners employ a staggered start-up mode for different heating zones to avoid instantaneous power overload causing voltage fluctuations.
Intensified Inspection Mechanism: For general materials, check the temperature every 20 minutes. For easily degradable materials, check the temperature every 5 minutes after the temperature exceeds the safety threshold. Temperature fluctuations should be controlled within ±2℃.
IV. Anti-Degradation Optimization
Shortening High-Temperature Waiting Time: After the hot runner reaches production temperature, material feeding and injection molding must be completed within 30 minutes. Prolonged empty holding that allows the melt to stagnate is prohibited.
Controlling Easily Degradable Materials: When heating sensitive materials such as PVC/POM, conduct continuous and intensive inspections of odor and overflow conditions. If signs of degradation appear, immediately cool down and replace the melt in the runner.
Rapid Response to Temporary Faults: If equipment malfunctions during heating and material feeding cannot be completed in time, immediately lower the hot runner temperature to below the material's glass transition temperature to prevent prolonged overheating and degradation.
V. Digital Closed-Loop Optimization
Enable full-process data recording of the temperature control system, automatically generate heating curves, compare with historical standard curves to identify anomalies, and continuously iterate and optimize parameters such as heating rate and holding time, gradually reducing the total heating time by 15%~20% while completely avoiding the risk of material degradation.
