Based on your previous experience focusing on Husky hot runner K-type thermocouple calibration, sensor verification after heater leakage repair, hot runner full lifecycle maintenance, and your attempt to build a low-cost online calibration system using Python + LabVIEW, the following are complete and detailed operation steps for calibrating Husky hot runner sensors suitable for 320℃ high-temperature, high-load precision injection molding:
I. Pre-calibration Preparation
Tools and Qualification Confirmation: Prepare a CNAS-calibrated multi-channel high-precision temperature monitoring instrument, a 500V digital megohmmeter, a 0.8N·m torque screwdriver, high-temperature thermal grease, high-temperature resistant polyimide tape, and heat-insulating gloves.
Confirm that the calibration personnel are qualified to operate the hot runner temperature control system. Access the historical calibration log for this Husky hot runner system in advance, confirming the channel numbers and corresponding temperature measurement points of all sensors.
Equipment Pre-Check: Turn off high-power start/stop devices around the hot runner in advance to avoid grounding loop interference with the temperature measurement signal.
Confirm that the Husky temperature controller has no abnormal alarms such as heater overcurrent or sensor open circuit, and that the equipment is in a normal operating condition capable of heating up.
Peak Pre-heating: During non-production breaks, heat the hot runner from room temperature to 280°C and hold. 30 minutes before calibration, heat to 320°C and hold for 2 hours until the overall temperature of the runner is completely uniform and stable.
II. Sensor Pre-calibration Steps:
Appearance and Mechanical Inspection: Inspect each channel for thermocouple probes for bending, no green corrosion or wear through the armor layer, and no oxidation or burning of the connector pins. Ensure the probe is fully inserted into the bottom of the sensing hole without any gaps.
Tighten all sensor fixing screws to 0.8 N·m with a torque screwdriver to prevent probe loosening or displacement.
Insulation Performance Test:** Use a 500V digital megohmmeter to test the insulation resistance between the thermocouple core wire and the armor layer and hot runner shell for each channel. An insulation resistance ≥ 5 MΩ at room temperature is considered合格 (qualified).
After holding the hot runner at 320℃ for 2 hours, the high-temperature insulation resistance was retested, confirming an insulation resistance ≥0.1MΩ, indicating no potential insulation failure at high temperatures.
Basic Signal Verification: Using a multimeter in millivolt range, the thermocouple circuit was tested channel by channel to confirm continuity and no open circuits. The deviation between the output thermoelectric potential at room temperature and the theoretical value on the K-type thermocouple standard calibration table was ≤0.05mV.
III. On-site Data Acquisition Steps
Standard Probe Fixing: The standard temperature probe of the temperature monitoring instrument was firmly attached to the surface of the corresponding hot runner temperature measurement point using high-temperature resistant polyimide tape, ensuring complete contact between the probe and the metal surface of the runner without gaps.
After all standard probes for all channels were fixed, 15 minutes were allowed for the probe temperature to be fully synchronized with the runner temperature.
Parallel Data Acquisition: The multi-channel temperature monitoring instrument was started, set to acquire one set of data per minute, and continuously and automatically acquired 10 sets of synchronized temperature measurement data for all channels.
Run a pre-written Python automatic sampling script to directly connect to the Husky temperature controller via PTP industrial communication, synchronously and automatically collecting sensor temperature data from the controller without manual recording.
Data Validity Screening: Remove abnormal data jumps caused by equipment start-up and shutdown interference during the acquisition process, retaining 10 sets of continuous and stable valid temperature measurement data. Calculate the average deviation between the standard value and the sensor temperature measurement value for each channel.
IV. Husky Temperature Controller Parameter Correction Steps
Accessing the Calibration Menu: On the Husky temperature controller operation panel, enter the administrator password to access the "Sensor Calibration" menu and select the corresponding channel to be calibrated.
Confirm that the cold junction compensation reference value for the current channel is consistent with the measured room temperature value to avoid introducing additional errors through cold junction compensation.
Compensation Parameter Setting: Input the inverse value of the calculated average deviation for each channel as the temperature compensation parameter into the calibration offset field of the corresponding channel.
For systems with 8 or fewer channels, compensation parameters for all channels can be directly imported in batches. For systems with 16 or more channels, ensure that the parameters for each channel correspond one-to-one with the acquired data to avoid channel misalignment.
Parameter Saving and Implementation: After confirming that all channel compensation parameters have been entered, click the "Save and Implementation" button. The temperature controller will automatically load the new calibration parameters, complete the cold junction compensation reset, and the sensor temperature data will be updated immediately.
V. Post-Calibration Stability Verification Steps
Accuracy Re-verification: After the parameters take effect, wait 30 minutes and then synchronously collect 5 sets of temperature data again to confirm that the temperature deviation of all channel sensors is ≤ ±1℃, with no jumps or drifts.
Manually increase and decrease the set temperature by 10℃ three times each, observe the PID adjustment process, and confirm that the temperature overshoot is ≤ 2℃ and returns to the set value within 3 minutes.
Long-Term Stability Verification: Run continuously at the set temperature for 1 hour, monitoring the temperature data of all channels throughout the process, and confirm that the temperature fluctuation range is ≤ ±0.5℃, with no irregular jumps.
Simulate the start and stop of surrounding high-power equipment to confirm that the sensor temperature data has no instantaneous jumps and is not affected by grounding loop interference.
Final Acceptance of Trial Production: Initiate low-speed trial production, continuously producing 20 molds of products. Monitor sensor temperature data and heater current dynamic changes throughout the process, confirming no overcurrent alarms or signal interruptions.
Inspect the appearance and dimensional accuracy of the trial-produced products, confirming no defects caused by flash, insufficient glue, uneven stress, or other temperature anomalies, and that process stability fully meets standards.
VI. Calibration Closed-Loop Archiving Steps:
Automatic Data Upload: Automatically and synchronously upload all original data collected during this calibration, compensation parameters, and verification results to the existing MES system, generating a compliant calibration report with CNAS traceability.
Automatically update the sensor lifecycle maintenance log for this Husky hot runner system, recording the calibration time, deviation value, and next calibration cycle for each channel.
Dynamic Cycle Adjustment: For sensors with three consecutive calibration deviations < ±0.5℃, automatically extend the calibration cycle from 3 months to 6 months.
Sensors with calibration deviations exceeding ±2℃ will be marked as key monitoring targets, and the subsequent calibration cycle will be temporarily shortened to 2 weeks. The original cycle will be gradually restored after two consecutive calibration deviations stabilize.
