ELMI CM-6M: imbalance error above a certain speed, even without a rotor
What happened
Imbalance error (db) aborting runs; it triggered even with no rotor fitted, but only above a certain speed reported in the case.
What was checked
- The engineers turned the motor shaft by hand — bearings were free of roughness and play.
- They checked the rubber mounts under the motor — sound, not perished or collapsed.
- They confirmed the fault appeared only above a certain speed, which pointed away from a true imbalance load.
Cause
With bearings and mounts confirmed sound, the cause in this case was a drifted imbalance threshold calibration: above a certain speed the sensor read normal vibration as imbalance, even with the rotor off.
What was done
The fix was a recalibration of the imbalance threshold — a procedure from the manufacturer's service documentation, done by authorised personnel — carried out only after the bearings and mounts had been verified sound. The error did not return.
Safety
Imbalance protection is a safety function on a machine that stores serious rotational energy: never raise or recalibrate the threshold before bearings, mounts and rotor are verified sound, and confirm a smooth, balanced spin before returning the unit to use.
Lesson: A speed-dependent imbalance alarm means check the mechanics first, and only recalibrate the threshold through the manufacturer's authorised procedure once the machine is proven mechanically sound.
Covered in the course: Lab Analyser Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.