The layout position and density of hot runner thermocouples not only control temperature measurement accuracy, but also directly affect the service life and working load of heating coils. Unreasonable thermocouple arrangement will cause long-term overheating or frequent power fluctuation of heating coils, accelerating aging, burnout and local damage, increasing mold maintenance cost.
If the thermocouple is arranged too close to the heating coil, it directly senses the radiant high temperature of the heater rather than the actual runner temperature. The controller mistakenly judges the temperature as too high and continuously reduces output power, resulting in insufficient melt temperature, poor fluidity and molding defects. Conversely, if the measuring point is too far away from the heating zone, the sensed temperature lags seriously, the controller keeps high-power heating for a long time, making the heating coil work under overloaded high temperature for a long time, accelerating wire aging, insulation carbonization and easy burnout.
Unbalanced thermocouple layout in multi-zone manifolds causes frequent frequent power rise and fall of individual heating coils under PID automatic adjustment. Repeated current impact produces thermal fatigue of heating wire, shortening service life significantly. Reasonable layout should keep thermocouple at the moderate position of the heating zone, away from direct radiation of the coil, accurately feeding back runner temperature, making the heating coil work in stable power output state, reducing frequent load changes, and extending the overall service life of both heater and thermocouple.
