A customer encountered an issue with temperature control malfunction on their Mirel 9118 controller for an injection molding machine and sent us the controller screen display.
From the display, we identified Error Code 030, which indicates a thermocouple disconnection error.
Further examination of the controller display revealed that the temperature reading for the second section was abnormal, with an actual temperature significantly higher than the set temperature.
This suggests that the thermocouple in the second section may have failed, preventing the controller from accurately reading temperature data, which triggered the alarm.
Testing Method
Step 1: Use a multimeter to measure the thermocouple resistance.
Solution
If the thermocouple is confirmed to be faulty, replace it with a thermocouple of the same specifications.
After replacement, recalibrate the temperature control system and verify that the temperature readings return to normal.
Testing Method
Check whether the thermocouple terminal connections are loose, oxidized, or disconnected.
Solution
If loose connections are found, re-secure the terminal connections.
If the wiring is aged or damaged, it is recommended to replace it with high-temperature-resistant thermocouple wiring.
Testing Method
Short-circuit the second thermocouple’s I/O point on the mainboard to see if the issue persists.
If the alarm still occurs after short-circuiting, the issue is likely with the mainboard.
If the alarm disappears after short-circuiting, then the problem is not with the mainboard.
Solution
If the mainboard is confirmed to be faulty, it requires repair or replacement.
Through the above step, we identified that the root cause of the issue was a controller mainboard failure.
Preliminary analysis suggests that the thermocouple wiring might have accidentally come into contact with the heating wire, causing electrical current to transfer to the mainboard and overload it.
To keep production running on schedule while awaiting a permanent repair, we implemented a temporary workaround:
Step 2: Disable the temperature display for the second section on the controller to make the system ignore the faulty sensor.
This approach allows the machine to keep running without replacing the mainboard immediately.
However, we strongly recommend repairing or replacing the damaged controller mainboard as soon as possible to ensure long-term system stability.
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