Technical Points of On-site Rapid Calibration of Hot Runner Thermocouples

Due to the limitations of production jobs and order delivery time, it is frequently impossible to halt production for an extended period of time in the daily injection molding production process in order to perform professional laboratory accuracy calibration. Therefore, technical staff can quickly identify temperature measurement errors, quickly correct drift deviations, restore accurate temperature control effects, and resolve temperature inconsistency issues without interfering with regular production progress by mastering the on-site rapid calibration technology of thermocouples. For workshop daily troubleshooting and daily performance assessment, this simple and effective calibration approach is very useful.

A high-precision industrial infrared thermometer with confirmed accuracy is the most popular instrument for quick calibration on-site. Make that the infrared measuring device is operating normally and that the detection data is precise and useful before calibrating. Avoid the temperature rise and fall transition period with unstable heat distribution, choose the stable constant temperature stage of hot runner operation as the optimal calibration time point, and wait until all temperature zones reach the predetermined process temperature and continue operating steadily for more than 30 minutes before beginning data comparison work. At this stage, the flow channel's internal heat distribution is uniform, and the temperature data that is detected is more accurate and trustworthy, accurately reflecting each measuring point's actual operating temperature.

The specific calibration procedure involves aiming the infrared thermometer at the metal matrix close to the thermocouple probe installation position, maintaining a suitable measuring distance, avoiding interference from nearby heat sources and air flow, and precisely measuring the hot runner metal's actual surface temperature near the measuring point, which is considered the real reference temperature. Next, note the temperature display value that the corresponding thermocouple on the temperature controller feeds back, compare the two sets of data one by one, compute the temperature difference deviation between the actual and displayed temperatures, and categorize and record the positive and negative deviations of each temperature zone, respectively.

Perform quick data compensation repair based on the error condition after receiving the precise deviation measurement. Set a positive compensation value in the temperature control system to increase the feedback reference value if the thermocouple's displayed temperature is lower than the actual measured temperature; set a negative compensation value to lower the display benchmark if the displayed temperature is higher than the actual temperature. When setting compensation parameters, adhere to the principle of small adjustment and multiple verification. Don't enter excessive compensation values all at once; instead, adjust a small range of parameters each time, wait for the system to stabilize, and then perform secondary temperature comparison and confirmation until the displayed temperature is essentially consistent with the actual infrared measured temperature and the error is controlled within the permitted production range.

On-site fast calibration must finish basic performance evaluation tasks in addition to temperature data deviation correction. Examine each thermocouple signal's feedback speed as the temperature rises and falls, and eliminate any products that clearly exhibit a slow reaction or data lag. It can be determined that the internal performance of thermocouples with excessive deviation that cannot be corrected by compensation parameters alone has significantly aged and drifted. These thermocouples should be marked in advance to schedule shutdown replacement as soon as possible to prevent affecting product quality in subsequent formal production.

It should be mentioned that professional constant temperature equipment laboratory calibration cannot be fully replaced by on-site fast calibration; it is only utilized for daily error correction and traditional performance inspection. Infrared temperature measurement has certain small intrinsic inaccuracies that are influenced by the external ambient temperature, heat dissipation conditions, and measuring angle. To guaranty that the total temperature measurement accuracy of the thermocouple group satisfies the high-standard production requirements, businesses must schedule regular full-range professional precision calibration even after performing many on-site fast calibrations. Effective use of on-site rapid calibration technology may immediately resolve a variety of small temperature deviation issues in production, stabilize the molding quality of injection products, and significantly increase the efficiency of on-site fault debugging and process optimization.