After replacing the hot runner heating element, a systematic commissioning process is essential to ensure temperature control accuracy, electrical safety, and process stability. The following is a complete commissioning procedure and verification points:
I. Electrical Performance Retest (Safety First)
|
Test Item |
Standard Requirements |
Operating Method |
|
Heating Element Resistance |
Deviation from original manufacturer's nominal value ≤ ±5% |
Measure cold resistance using a digital multimeter. For example, a 200W element should be approximately 24.2Ω. |
|
Insulation Resistance to Ground |
≥ 5MΩ (tested with a 500V megohmmeter) |
Test the insulation between the heating rod and the mold shell after power is off. Powering on is strictly prohibited if the insulation resistance is below 1MΩ. |
|
Thermocouple Continuity and Resistance |
PT100 at 25℃ is 109.6Ω±1Ω |
Check if the temperature sensing wire is open-circuited, short-circuited, or has a drifting resistance value. |
Key Note: Any abnormal electrical parameter requires re-inspection. Operation with defects is prohibited.
II. Temperature Control System Calibration and PID Tuning
No-load Heating Test
Set each temperature zone to a typical processing temperature (e.g., 230℃).
Observe whether the heating curve is smooth; the time to reach the set value should be ≤ 15 minutes.
After stabilization, the fluctuation range should be ≤ ±2℃.
PID Parameter Optimization
If the controller supports self-tuning (e.g., Siemens PID Wizard), start automatic calibration.
If manual tuning, use the decay curve method:
First, turn off I and D operations, only adjust P, so that the system exhibits a 4:1 decaying oscillation.
Use a metrology-certified standard thermocouple placed side by side with the original sensor.
Compare the readings at three points: 200℃, 250℃, and 300℃.
If the deviation is > ±1.5℃, a compensation coefficient needs to be entered in the controller.
III. Thermal Uniformity Verification (Thermal Balance Adjustment)
Multi-point Temperature Distribution Measurement
Use an infrared thermometer to scan the nozzle tip, the surface of the manifold, and the root of the hot nozzle.
The temperature difference between nozzles on the same manifold should be ≤ ±3℃ Deviance between nozzle tip and set value ≤ ±2℃
Thermal Balance Confirmation
Run continuously for 30 minutes and record the temperature fluctuation trend of each zone.
If a zone remains consistently low, check:
Is the heating element misaligned?
Is there partial blockage in the manifold channel?
Is the insulation layer damaged?
Industry Standard: According to GB/T 38507-2020 Technical Conditions for Hot Runner Systems in Injection Molds, the maximum temperature difference between each zone of the hot runner system under stable conditions shall not exceed 5℃.
IV. Process Verification and Trial Molding Test
|
Process Indicators |
Acceptance Criteria |
Judgment Basis |
|
Filling Integrity |
All cavities are completely filled, no short shots |
Check product weight consistency; single-piece deviation ≤ ±1%. |
|
Appearance Quality |
No scorch marks, silver streaks, or flow marks |
Visual inspection with a magnifying glass, especially near the gate. |
|
Dimensional Stability |
Critical dimension fluctuation ≤ ±0.05mm |
Use a coordinate measuring machine to inspect at least 3 samples. |
|
Weld Line Strength |
No obvious weak lines |
Tensile test or ultrasonic testing verification. |
Recommended Operation: Mass production can only begin after producing 10 consecutive qualified parts.
V. Post-Debugging Document Archiving
Record the new component model, batch number, and installation location.
Save the resistance, insulation value, and PID parameters before and after debugging.
Attach an infrared thermal image (if available) or temperature curve screenshot.
Complete the "Hot Runner Maintenance and Debugging Confirmation Form," signed by the operator and supervisor.
