How to Avoid Thermocouple Damage During Hot Runner Mold Installation and Debugging

One of the main reasons of early damage and premature failure of thermocouples is improper operation during hot runner mould installation, assembly and machine troubleshooting. Standardised operation criteria may effectively prevent man-made damage, maintain the integrity of thermocouple construction and the stability of temperature measuring performance, and eliminate unnecessary replacement costs and debugging time.

Before installation of thermocouple in the stage of mould construction, the reserved temperature measuring holes of the manifold and the nozzle should be properly cleaned to remove iron filings, oxide scale, oil grime and residual carbon deposits. Any hard particles remaining in the hole will scratch the surface of the sheath when the probe is inserted, or crush and deform the internal temperature measuring head, resulting in hidden risks such as short circuits and drift. Do not violently knock and press the thermocouple into the hole. Insert it gently down the axis of the hole so that there is no skew force which will cause the probe to bend and distort by extrusion.

In the wiring and fixing connection, the thermocouple wire harness should follow the preset wire groove of the mould, avoid crossing the mould splitting surface and sharp steel edges, and prevent the wire harness from being crushed and cut when the mould is closed. Ensure enough slack in the wiring harness based on the mould opening stroke, manage the bending radius to avoid severe right angle bends, and prevent internal thermoelectric wire breakage due to long-term bending fatigue. The connector should be mounted in a hidden and ventilated position away from the heating ring, to avoid the high temperature baking and ablation of the terminal.

The temperature cannot be set at an excessively high value at one time in the mould testing and heating debugging process. Gradually increase heat in steps so that there is no immediate high temperature influence on the thermocouple and ageing acceleration. Real time observation of the temperature display of each zone of the controller. Stop heating immediately to determine if there is anomalous jump, open circuit and drift warning, do not run with faults to avoid the local overheating burning the thermocouple and heating ring.

After debugging is completed and the mould is taken out of the machine, the thermocouple connector should be secured from moisture and dust, the wire harness should be sorted out and bundled, and the probe location should be protected from extrusion and collision when handling and storing the mould. After long-term usage, it is necessary to regularly check the tightness of the fixed joint, prevent loosening and virtual connection induced by vibration, and minimise early damage concealed threats in time. The full process operation from installation,wiring,debugging to storage may be standardized,so as to drastically reduce the damage rate of hot runner thermocouples and prolong the overall service life.