First, find the cold solder joint as soon as possible.
First, unscrew the thermocouple junction box and turn off the electricity. To rule out loose terminals creating false cold solder junctions, retighten every terminal.
As you watch the temperature on the temperature controller, gently jiggle the thermocouple wires close to the solder connection. Find the cold solder junction where the shaking causes the signal to fluctuate.
Step 2: On-site temporary reinforcement
Once the cold solder junction has been located, use fine sandpaper to carefully remove the oxide layer on the surface. Next, maximise the contact area by tightly twisting the two thermocouple wires together with tweezers.
To stop further short circuits between the wires and shield it from dust and grease, cover the connection with a high-temperature insulating sleeve after temporary twisting.
Step 3: Short-term signal stabilisation techniques
In order to prevent false alarms from the temperature control system, activate the short-term program filtering function in the PLC temperature control program after the emergency handling is finished. This will appropriately increase signal damping and filter out tiny temperature fluctuations caused by the cold solder joint.
By adding a ferrite core to the thermocouple signal line, anomalous temperature signal fluctuations are further reduced by suppressing electromagnetic interference from the motor and frequency converter.
Emergency Operation Precautions: A designated individual is required to check the temperature profile every two hours following temporary intervention. Replace the thermocouple and turn off the machine right away if temperature swings are more than ±5°C.
Only temporary manufacturing line maintenance is supported by this emergency plan. In order to entirely minimise the danger of faulty soldering and prevent eventual thermocouple failure that could result in uncontrolled hot runner temperature management, thermocouple connections must be resoldered during non-production hours.
This emergency handling technique allows for the quick restoration of steady temperature control system performance without the need to replace the thermocouple and is completely adaptable to on-site repair circumstances in hot runner injection moulding production lines.
