How to determine if a hot runner temperature control box needs calibration

Whether a hot runner temperature control box needs calibration should be determined based on a comprehensive assessment of four dimensions: temperature accuracy, process stability, equipment alarm feedback, and service life. The following are systematic judgment criteria, covering technical performance, operational anomalies, and management standards, ensuring scientific and feasible decision-making.

 

I. Excessive deviation between displayed and measured temperature values ​​(most direct criterion)

On-site comparison method: Use a metrology-certified standard temperature measuring instrument (accuracy ±0.1℃) and a thermocouple inserted side-by-side into the same temperature measuring port. Read the value after the system has stabilized for 10 minutes.

Deviation ≤ ±1℃: System normal, no calibration required.

Deviation > ±1℃ and ≤ ±2℃: Calibration recommended to prevent process drift.

Deviation > ±2℃: Calibration required immediately, posing a quality risk.

Example: Set temperature 250℃, temperature control box displays 253℃, standard instrument measures 249℃, deviation +4℃ → Calibration required.

 

II. Abnormal Process Stability (Indirect but critical production signal)

Abnormal Phenomenon	Possible Cause	Does it indicate calibration requirement?
Product weight fluctuation > ±3% under the same mold and parameters	Temperature fluctuation causes melt viscosity change	Strong correlation
Product exhibits short shots, flow marks, silver streaks	Localized insufficient or overheating	Temperature control accuracy needs verification
Uneven color, localized carbonization	Overheating in a certain area, thermocouple inaccuracy	Calibration required
Dimensional variation exceeds tolerance by ±0.1mm per batch	Temperature control lag or drift	High Probability Correlation

Note: If other variables such as raw material batch, injection pressure, and mold wear have been ruled out, temperature runaway is the primary suspect.

 

III. Temperature Control Box Alarms and Abnormal Control Behavior

Alarm Type	Behavioral Characteristics	Calibration Required
Thermocouple Open Circuit	Sensor open circuit or poor contact; calibration is required after replacement	Forced
Frequent Over-Temperature/Under-Temperature Alarms	Actual temperature is not exceeded, but the system reports a false alarm	Temperature Feedback Distortion
Continuous PID Oscillation (above ±5℃)	Unable to stabilize after ruling out parameter setting errors	Abnormal Feedback Signal
Slow Heating Response	Set to 250℃, takes more than 30 minutes to reach the temperature	Sensor Aging or Carbon Deposits

Warning: If alarms are frequent but there is no hardware damage, over 90% of the time it is caused by temperature sensing system drift.

 

IV. Maintenance Cycle and Usage Scenarios Triggering Mechanisms

Usage Scenarios	Recommended Calibration Cycle	Calibration Triggered?
High-Precision Production (Medical, Electronic, Optical Components)	Every 3 Months	Calibrate upon expiration
Regular Injection Molding (Daily Necessities, Packaging)	Every 6–12 Months	Calibrate upon expiration
Multi-Shift Continuous Operation (>18h/day)	Every 3–6 Months	Mandatory Calibration for High-Frequency Use
Equipment Restart After Long-Term Shutdown (>30 Days)	-	Mandatory Calibration
Replacing Thermocouples, Temperature Control Modules, or Molds	-	Recalibration Required
Two Consecutive Calibration Correction Value Changes > ±1.5℃	-	Systematic Drift Exists, Cycle Needs to Be Shortened

 

V. Calibration Record Trend Analysis (Preventative Judgment)

Establish a calibration history archive, recording each correction value (Offset):

If three consecutive calibration correction values ​​show a unidirectional increase (e.g., -0.5℃ → +0.3℃ → +1.2℃), it indicates sensor aging, and the cycle should be shortened to 3 months.

If the correction value remains stable within ±0.2℃, the calibration period can be extended to 18 months, but quarterly spot checks are required.

It is recommended to use an electronic ledger with automatic alerts for approaching calibration dates to avoid human error.

Conclusion: Determining whether a hot runner temperature control chamber needs calibration should not rely on a single indicator, but rather on a four-tiered verification system: measured deviation + process anomaly + alarm feedback + periodic management. Any condition triggering "mandatory calibration" should be implemented immediately to prevent "operation with defects." Regular calibration is not a maintenance cost, but an investment in quality assurance.