A production line stoppage is rarely accompanied by explosions. More often, it loses power in silence. The servo motor vibrates a little more, the encoder loses a pulse, and the current increases by a fraction of an ampere. These subtle changes appear long before the controller alerts, but they're easy to miss when the workload is high. This is why early diagnostics are crucial, as they allow for data recording and comparison, allowing for the detection of operational anomalies. The sooner the team identifies a deviation, the greater the chance of incurring lower costs and avoiding unforeseen downtime. This results in better OEE, less pressure, and a smoother shift.
Every servo motor can communicate its status in advance; you just need to know which parameters to pay attention to and react before a minor anomaly escalates into a fault. Below, we present a collection of 5 symptoms that may indicate an impending failure.
Servo motor vibration
Vibration is the clearest indication of a problem with a servo motor. Exceeding the permissible vibration level doesn't always result in immediate failure, but in almost every case, it indicates increasing rotor imbalance, loose mounting bolts, or the initial stages of bearing damage. This symptom is easy to detect using a prediction system. If the value remains above the threshold for several consecutive measurement cycles, it's worth scheduling alignment and rebalancing. Detecting symptoms in time shortens the subsequent servo motor repair to routine mechanical reconditioning.
Errors in servo motor measurement systems
The precise position of a servo motor relies on feedback from an encoder or resolver. Random "position error" alarms or sudden spikes in the pulse counter can indicate a problem with the reliability of the system. Even a small deviation can impact measurement accuracy. The cause can be as simple as internal contamination, wear of mechanical components, or poor electrical connections. The first step in diagnosis is to test the measurement system using a specialized analyzer adapted to the given interface.
During the measurement, the actual operating conditions of the device should be reproduced as accurately as possible, taking into account parameters such as ambient temperature and humidity. All of these factors can affect the operation of the measurement system factors accompanying engine operation, such as vibrations, overloads or difficult working environment.
Increase in gear vibration in the band
A servo motor typically emits uniform, predictable vibrations. A sudden peak in the spectrum indicates progressive motor wear, loss of alignment or balance, or drivetrain wear. Excessively high peaks in the vibration spectrum indicate excessive wear in the drivetrain, such as the gears, and increased resistance torque in these components. It's a good idea to measure at nominal load and at a servo motor speed corresponding to the mechanism's resonance. If the amplitude increases quarter-on-quarter, a drivetrain disassembly and audit should be scheduled. If necessary, the gear should be replaced or the clearance adjusted before it causes a failure of the entire unit.
Uneven servo motor torque
A servo motor should deliver smooth, constant torque throughout the entire speed range. When a regular torque pulsation appears over time, we speak of torque ripple. Oscillation exceeding ±5% of the rated value can indicate a loss of electromagnetic force or local rotor deformation. It is often invisible at idle, but becomes apparent only under load, when the torque sensor or the inverter's oscilloscope function records increases and decreases in force. Causes include demagnetization of the magnet segment, gear backlash, clutch misalignment, the condition of the motor windings, or mechanical damage to the magnetic cage. In such cases, it is recommended to measure it at operating speed and compare it with the reference value at the time of installation. Increasing torque fluctuations lead to shaft vibration and uneven motor wear, ultimately leading to irreversible failure.
Increasing power consumption with unchanged operation
When the production program does not change speed or torque, and the energy counter increases, it indicates increasing motor load or thermal or current overload. Early trend analysis allows for planning diagnostics and possible service before the servo motor reaches an alarm state. Increasing current is usually a phenomenon resulting from another fault and, consequently, a potential cause of damage. It's best to measure it during a repeatable operating cycle, recording the phase current and winding temperature. If, after excluding environmental influences, the current still exceeds the assumed threshold, it's worth collecting a thermal log. Elevated temperature reduces the life of winding insulation by half, and the loss of efficiency increases energy costs and the load on the inverter.
Early diagnosis of these faults can protect the entire production line from unwanted and costly downtime. Rising power consumption, increased vibration, uneven servo motor torque, or random encoder errors are all signs that it's time to schedule a service visit.
