Daily Inspection Checklist for Hot Runner Thermocouple System

For hot runner thermocouple systems, creating a systematic daily inspection checklist is a crucial step in achieving preventative maintenance, removing hidden flaws beforehand, lowering unexpected production shutdown failures, and stabilizing injection molding production quality. In order to guaranty that all hot runner thermocouples and related auxiliary lines are always in optimal operating condition, workshop maintenance staff and on-site operators can perform an all-around quick inspection of the entire temperature measuring system in accordance with the unified checklist every day before beginning production and after shutting down, record abnormal items in detail, and schedule targeted rectification and maintenance in a timely manner.

The first section is the pre-start-up visual appearance inspection item, which is primarily used to verify each thermocouple's surface condition and exterior structural integrity. First, examine each nozzle and manifold thermocouple's metal probe to see if it is bent, worn, oxidized, blackened, or rusted. Verify that the probe's surface is free of scratches and extrusion deformation, and make sure the sensing end can fit closely to the heating hole wall normally. In order to prevent poor heat conduction and signal instability brought on by loose installation, secondly, examine the firmness of each thermocouple's installation, determine whether the locking thread is loose and whether the entire sensor is displaced and skewed, and promptly re-lock and fix any loose sensors.

Third, examine the thermocouple high-temperature connecting wires' appearance; note whether the outer insulating skin is aged, hardened, cracked, faded, and damaged; look for oil dirt adhesion and high-temperature scorching marks on the wire body; and designate the wires with significant aging damage for replacement as soon as possible. Fourth, check the thermocouple wiring plugs, terminal heads, and external junction boxes; remove any accumulated dust, condensed water, and rust stains from the terminals; make sure the wiring terminals are not loose, oxidized, or virtually connected; and make sure the signal circuit connection is steady and dependable.

After the appearance inspection is qualified, the second section is the circuit and signal function test item, which is used to confirm the thermocouple system's proper signal feedback and normal conduction. First, turn on the temperature controller power supply while there is no heating output. Next, make sure that all temperature zone display screens are able to display real-time temperature values normally. Lastly, make sure that there are no blank screens, random code displays, negative temperatures, or other unusual display phenomena. Finally, make sure that the thermocouple loop's open circuit and short circuit faults are promptly fixed.

Second, manually adjust the temperature rise parameters, perform a low-temperature trial heating operation, monitor the temperature rising trend and data change speed of each temperature zone, assess the sensitivity and normality of the temperature feedback response, and filter out the sensors with slow signal response and noticeable temperature lag. Third, make sure the temperature measurement accuracy satisfies the production process standards by using portable standard temperature measuring devices to perform spot checks and comparisons on the actual temperature and display temperature of key temperature zones, record the temperature deviation value, and mark the thermocouples with excessive error for calibration or replacement.

The third section is the working environment and related accessory inspection item, which focuses on examining how the external usage environment affects thermocouples' functioning stability and service life. To prevent excessive heat loss that could cause anomalous temperature control and accelerate thermocouple aging, first inspect the hot runner's surrounding heat preservation structure and make sure the heat insulation gaskets and plates are complete. Second, keep the thermocouple installation position dry, check for water seepage and splashing around the mold cooling water pipeline, promptly address any water leakage issues, and guard against moisture corroding the sensor's internal structure.

Third, reorganize the thermocouple wiring harnesses inside the mold. Verify that the wires are organized neatly, that there is no extrusion friction with moving mold components, that the reserved bending margin is adequate, and that the movement of the mold's opening and closing prevents wire core breakage. Fourth, assess the ventilation and dust removal conditions in the on-site workshop, lower the concentration of oil smoke and plastic dust floating around the hot runner, and slow down the rate at which dirt accumulates on the thermocouple surface.

The data record and hidden hazard sorting item make up the fourth section. Once every inspection item has been finished, consistently complete the daily inspection record form, note the serial number, installation location, temperature deviation state, degree of appearance damage, and other specific details of each abnormal thermocouple individually, and categorize the hidden hazards based on the severity level. Mark the next re-inspection time for slightly abnormal sensors that can be used after calibration; schedule a replacement for sensors that are moderately aging within three working days; and cease using severely malfunctioning thermocouples that exhibit significant temperature deviation and unstable signals on the same day.

Additionally, create a complete closed-loop management mode of inspection, record, maintenance, summary, and optimization by summarizing the inspection situation each week, counting the failure rules and aging laws of hot runner thermocouples in various production positions and raw material processing environments, and making targeted adjustments to the reserve quantity of spare parts and the regular maintenance cycle.

More than 90% of sudden temperature control faults can be eliminated from the source by strictly adhering to the daily standardized inspection of the thermocouple system in accordance with the inspection checklist. This can also effectively extend the overall service life of hot runner temperature measuring components, keep the hot runner temperature control system operating efficiently and steadily for a long time, and lay the groundwork for stable injection molding production, high product yield, and low overall operation costs.