I. Preparatory Work
Tools needed: High-precision digital multimeter, oscilloscope, standard signal generator, spare resistors/capacitors of corresponding specifications, anti-static wrist strap.
Safety Confirmation: Cool the hot runner system to below 60℃, disconnect the high-voltage heating output circuit of the temperature controller to avoid the risk of electric shock or accidental heating during live operation.
Record Reference: Export the original RC parameters, filter cutoff frequency, and interference attenuation target value before drifting as a reference for calibration and repair.
II. Fault Location Steps
Use a digital multimeter to directly measure the actual resistance and capacitance values of the RC network to identify the specific drifting component and distinguish between resistance and capacitance drift.
Use a standard signal generator to input standard sine waves of different frequencies to the temperature controller input terminal. Use an oscilloscope to observe the waveform at the filter output terminal, measure the current actual filter cutoff frequency and interference attenuation amplitude, and confirm the specific value of the drift exceeding the limit.
Investigate the surrounding environment for any newly added sources of interference or damage to the temperature sensing wires, ruling out "false drift" caused by external factors.
III. Rapid Calibration and Repair Operations
If the parameter drift is only minor (deviation ≤30%): Use the built-in dynamic RC adjustment menu on the temperature controller to fine-tune the resistance and capacitor input settings, calibrating the actual filter cutoff frequency back to the set value, ensuring the target interference attenuation is ≥20dB.
If the component hardware drift exceeds the standard (deviation >30%): Power off and remove the drifting resistor/capacitor, replace it with a high-precision temperature drift component of the same specification, and remeasure the capacitance value after soldering, confirming the deviation from the nominal value is ≤5%.
Post-calibration parameter verification: Re-enter the standard test signal, confirming that the total RC time constant is ≤200ms, the temperature signal delay is ≤200ms, and all performance indicators return to the acceptable range.
IV. On-site Verification and Closed-Loop Operation
Restore the hot runner heating loop, start the heating process, observe the temperature control curve, and confirm there are no jumps, overshoots, or oscillations.
Simulate the maximum interference conditions in the field to verify the stability of the filtering effect, with temperature reading fluctuations ≤ ±0.5℃.
Enter the repaired RC parameters, calibration time, and information on replaced components into the process file, and update subsequent calibration cycles synchronously to prevent similar drift problems from recurring.
