Static Basic Verification: Measure the thermocouple circuit's resistance using a multimeter when the power is off. Verify that there are no high impedance or sporadic open circuit problems, and that the resistance value differs by ≤10% from that of a qualified thermocouple of the same specification.
Calculate the insulation resistance between the shielding layer and the thermocouple poles. To ensure that there is no risk of leakage or short circuit and that the insulation layer was not damaged during the repair procedure, the value should be ≥1MΩ.
Verify that the thermocouple calibration numbers and compensating wires match exactly, and that the wiring terminals are firmly attached. Verify that no connections are loose or faulty.
Dynamic Temperature increase Test: Set the target temperature to the typical production temperature, turn on the hot runner temperature management system, and watch the temperature increase curve. Verify that there are no lags, leaps, or abrupt increases or drops in the temperature as it climbs in accordance with the predetermined value.
Shake the thermocouple solder junctions and wire locations lightly while the temperature rises. The temperature controller's display should not exhibit any unusual variations, indicating that the possible cold solder connection problem has been totally resolved.
Temperature Stability Verification: Run the temperature controller self-tuning (AT) software to automatically adjust the system to the repaired thermocouple characteristics and optimise PID parameters once the hot runner achieves the desired temperature.
Record the temperature fluctuation range while operating continuously at a steady temperature for at least 30 minutes. Verify that there are no unidirectional drifts or random jumps and that the temperature deviation is steady within ±1°C.
Using an infrared thermometer, determine the actual temperature at the relevant location in the hot runner and compare it to the value shown on the temperature controller. The variance should be ≤±3°C, indicating that the precision of the temperature measurement is up to par.
Verify the production conditions by starting formal injection moulding production and continuing for a minimum of two full moulding cycles. Throughout the process, keep an eye out for any abnormal temperature jumps or alarms from the temperature control system. Additionally, make sure that the product's moulding status is steady and free of faults linked to flash, short-filling, or other temperature control issues.
Verify that the complete temperature control loop functions steadily by confirming that the load current and power displays of each heating section of the hot runner are normal, with no unusual overload or current jumps.
It is 100% certain that the hot runner temperature control system has fully recovered from the cold solder joint failure and can resume regular long-term production operations once the aforementioned four verification stages are finished.
