Influence of Different Cooling Water Circuit Layout on Thermocouple Temperature Measurement

The layout position, water flow speed, and distance from the hot runner of the cooling water circuit, which is a crucial component of the mold temperature control system, will clearly cause heat dissipation interference on the surrounding hot runner components. This indirectly affects the actual temperature measurement accuracy and working stability of nearby thermocouples and can easily result in invisible temperature control deviation in production.

The low-temperature circulating cooling water will continually remove the surface heat of the hot runner metal matrix if the cooling water channel is positioned too close to the hot runner manifold and nozzle temperature measuring locations. The real melt temperature of the flow channel is clearly higher than the metal temperature surrounding the thermocouple probe. The thermocouple's temperature reading is consistently low. The internal flow channel's real temperature will rise over the process standard as a result of the temperature management system automatically increasing the heating power for compensating. The thermal breakdown and carbonization of plastic raw materials can be easily caused by this covert overheating event, posing unseen risks to product quality.

The temperature differential between the hot runner's near-water area and central heating area will increase if the cooling water flow is too rapid and the heat dissipation intensity is too high. The entire hot runner system has an uneven zoning temperature due to irregular temperature feedback data from thermocouples in various locations. Each flow channel has a distinct melt fluidity, and the injection molding process is prone to flaws such uneven product filling, irregular shrinkage rate, and significant dimensional tolerance deviation.

Conversely, the total mold heat dissipation speed is slow and the heat accumulated by the hot runner cannot be dispersed in time if the cooling water circuit is too far from the hot runner. Long-term exposure to excessively high ambient temperatures causes the thermocouple's internal alloy wire core to age more quickly, decreasing the accuracy of temperature readings and reducing the sensing element's stable service life. In the meantime, a high overall temperature will decrease the overall efficiency of molding production and lengthen the time it takes for the product to cool and shape.

Additionally, the mold's unequal local heat dissipation will result from the irrational water circuit cross distribution layout, creating irregular temperature fluctuation locations. The displayed temperature values frequently move up and down unexpectedly, interfering with the temperature controller's regular constant temperature adjustment logic. This is because the thermocouples in these places are impacted by variable ambient temperature.

Early on in the mold design process, designers must carefully consider the distance between cooling water channels and hot runner temperature sensors, avoiding close proximity and direct confronting. Technicians must balance the mold heat dissipation efficiency and hot runner heating stability, as well as modify the circulating water flow speed in accordance with the real temperature feedback situation during the manufacturing and debugging process. In order to achieve the coordinated and stable operation of the hot runner heating system and mold cooling system, simultaneously increase the frequency of temperature calibration for thermocouples placed close to the water channel, promptly correct the temperature deviation caused by heat dissipation interference, and guaranty that the temperature data collected is accurate and useful.