How to verify successful repair after sensor replacement

I. Verification of static foundation after installation

Mechanical Installation Check: Verify thermocouple probe is completely seated in the bottom of the hot runner sense port with no gaps or hanging. The fixing screw torque shall be adjusted to 0.8 N·m. The probe shall not be bent by compression. The tail connector shall be properly tightened and latched.

Insulation Performance Test Use 500V digital megohmmeter to test the insulation resistance of thermocouple core wire, armor layer and hot runner shell. The insulation resistance at room temperature should be ≥5MΩ, without risk of short circuit and leakage.

Continuity Signal Verification Thermocouple Circuit Use a multimeter with a millivolt range to check the thermocouple circuit for continuity with no open circuits. The cold junction thermoelectric potential divergence at room temperature from the theoretical value in the K-type thermocouple standard calibration table should be ≤0.05mV without signal interruption problems.

II. Verification of the heating process in dynamic mode

Heating synchronization verification: The hot runner was heated from room temperature to the rated working temperature of 320℃ at a rate of 50℃/h. During the process, the temperature data of the thermocouples were recorded. It was confirmed that the sensor temperature response lag behind the heater current change is <30 seconds, without heating lag or jump phenomena.

Full-Channel Consistency Verification: The temperature data of all channels were synchronously compared at three important temperature nodes of 100℃, 200℃ and 320℃ with a high-precision temperature monitoring instrument calibrated by CNAS . The single channel temperature deviation was ≤±1℃

High-Temperature Insulation Re-Test After the hot runner was heated to 320℃ and kept at this temperature for 2 hours, the high-temperature insulation resistance of the thermocouples was re-tested. The insulation resistance was confirmed to be ≥0.1MΩ, which means there is no insulation failure at high temperatures.

III. Verification of the temperature control system linkage

PID Control Stability Verification: Increase and decrease the set temperature by 10℃ three times respectively. Observe the process of PID regulation for the temperature controller, verify that the temperature overshoot is ≤2℃, it returns to the set value within 3 minutes, and there is no continuous oscillation and over-temperature warning.

Long-term stability verification: run continuously for 4 hours, record temperature data every 10 minutes, and verify that the thermocouple temperature data has no abnormal jumps or baseline drift, and the temperature fluctuation range is ≤±0.5℃ throughout.

Grounding Interference Immunity Verification: Simulate the start and stop of surrounding high-power equipment, confirm that the thermocouple temperature data has no instantaneous jump, is not affected by the grounding loop interference, and the CMRR common-mode rejection performance meets the standard.

IV. Verification of Final Production Conditions

Small batch trial production verification: Continuously build 20 pieces of modules, monitor the continuous thermocouple temperature data and the dynamic change of the heater current throughout the process, and verify that there is no overcurrent alert and aberrant signal interruption.

Product Yield Verification: Verify the trial production products for visual and dimensional accuracy to check no flaws caused by aberrant temperatures, such as burrs, lack of glue, or uneven stress, and the process stability has been fully restored.

Data Archiving Confirmation: Record the thermocouple serial number, complete-process verification data and calibration parameters of this replacement in the hot runner sensor's entire lifecycle maintenance log for benchmark reference data for following periodic inspections.