Troubleshooting of Servo Motor Bearings: Causes and Solutions
During the long-term operation of servo motors bearings, as the core rotating components, their failure directly leads to increased equipment vibration, reduced precision and even downtime, causing unnecessary losses to production. When the bearing malfunctions, accurately locating the cause of the fault and quickly resolving it is the key to ensuring the stable operation of the equipment. This article will focus on three common types of faults, share practical diagnostic methods and targeted solutions to help you troubleshoot problems efficiently, reduce maintenance costs, and fully demonstrate professional technical service capabilities.
1. Three Common Types of Faults: Phenomenon + Core Cause Breakdown
Faults of servo motor bearings are often related to installation, lubrication, material or working conditions mismatch. The following three types of faults account for more than 80% and can be targeted for troubleshooting:
1. Abnormal vibration: Equipment "jitter warning", mostly due to installation deviation
Typical phenomenon: Obvious shaking occurs when the motor is running, causing the whole machine to resonate; The positioning accuracy of precision equipment decreases; Operating noise increases as vibration intensifies.
Core cause:
Installation deviation: too tight or too loose fit between the shaft and the inner ring of the bearing; The bearing is tilted during installation, and the coaxiality deviation exceeds 0.02mm;
Part wear: Pitting and spalling on the raceways or rolling elements of the bearing, resulting in rotational imbalance;
Improper selection: The use of ordinary deep groove ball bearings in high-speed scenarios causes resonance due to insufficient critical speed.
2. Excessive temperature rise: Bearing "heat alarm", the root cause is lubrication or heat dissipation
Typical phenomenon: After the motor has been running for 1 hour, the temperature at the bearing end exceeds 80°C (normal range: 40-70°C); In severe cases, the grease melts and leaks, accompanied by an unpleasant smell; In extreme cases, it can cause the bearing to jam.
Core cause:
Lubrication failure: Incorrect grease selection (such as using regular mineral grease in high-temperature scenarios), insufficient lubrication (filling less than 20% of the internal space of the bearing), or too long lubrication cycle (aging and deterioration of the grease);
Poor heat dissipation: Motor heat dissipation channels are blocked, bearing seals are too tight to dissipate heat;
Overload: The actual load exceeds the rated dynamic load of the bearing, causing increased friction and heat generation.
3. Shortened lifespan: Failure before reaching the designed lifespan, mostly due to material or working condition compatibility issues
Typical phenomenon: The operating time of the bearing is much shorter than the L10 design life; Failure is characterized by severe raceway wear, broken rolling elements or cage damage.
Core cause:
Material fatigue: Common bearing steel experiences a decline in
material strength and premature fatigue cracking under high-frequency impact loads or high-temperature conditions;
Improper working condition adaptation: New energy vehicle high-voltage platforms do not use electro-corrosion-resistant bearings, resulting in raceway electro-pitting; Sealed bearings are not used in harsh environments, and dust intrusion intensifies wear;
Installation damage: Hammering the outer ring of the bearing with a hammer during installation causes hidden damage to the raceway, posing a lifespan hazard.
Two - and three-step troubleshooting method: Quickly locate the root cause of the problem
Fault diagnosis requires a combination of "sensory judgment + tool detection". The following three-step method is simple and efficient, suitable for on-site practice:
1. Locate by sound: Make a preliminary judgment based on the type of noise
Press a screwdriver or stethoscope against the bearing end cover and listen for the operating noise corresponding to the type of fault:
Uniform "hum" : mostly due to installation deviation or a tight fit between the inner ring of the bearing and the shaft, resulting in increased rotational resistance;
Shrill squeaking: Insufficient or aged grease, dry friction between the rolling elements and the raceways;
Irregular "clacking" : pitting, flaking, or cage damage on the raceways or rolling elements;
High-frequency whistling: Insufficient critical speed in high-speed scenarios, causing resonance.
2. Temperature monitoring: Use data to determine the degree of heat
Use infrared thermometers or temperature sensors to monitor the temperature at the bearing ends and determine the operating time:
Normal range: After running for 1 hour, the temperature is 40-70℃ and tends to stabilize without a continuous upward trend.
Minor faults: Temperature 70-80°C, accompanied by a slight odor, mostly due to insufficient lubrication or poor heat dissipation;
Serious fault: If the temperature exceeds 80°C and rises by more than 5°C within 10 minutes, it may be due to lubrication failure or overload and requires immediate shutdown.
3. Precision detection: Use tools to quantify the extent of the fault
Core inspection indicators: Radial runout (measured with a dial indicator) coaxiality (measured with a laser alignment instrument) :
Radial runout: Normal for P5 grade bearings ≤0.005mm, P4 grade ≤ 0.003mm; If it exceeds the standard by more than twice, it indicates raceway wear or installation deviation;
Coaxiality: The coaxiality between the motor shaft and the bearing housing should be ≤0.02mm. If it exceeds the limit, the vibration is caused by installation deviation.
Fit clearance: Check the fit between the shaft and the inner ring of the bearing with a feeler gauge. If it is too tight (no clearance) or too loose (clearance > 0.01mm), it is abnormal.
3. Targeted Solutions: Address the root cause of the problem
Depending on the type of fault and the diagnosis result, the following solutions can be implemented directly while taking cost and effect into account:
1. Abnormal vibration: Optimize installation and selection Installation adjustments:
Install using a hydraulic nut or hot mounting method (insert the shaft after heating the bearing to 80-100°C), avoid hard hammering;
Use a laser alignment instrument to correct coaxiality, ensuring that the deviation is ≤0.02mm;
The shaft fits the inner ring of the bearing with a transition fit (such as H7/k6), which neither loosens nor compresses the bearing.
Selection optimization: For high-speed scenarios (speeds ≥ 10,000 RPM), replace with angular contact ball bearings or hybrid ceramic bearings to increase the critical speed.
2. Excessive temperature rise: Upgrade lubrication and heat dissipation
Lubrication scheme optimization:
Synthetic high-temperature grease is selected for high-temperature scenarios (≥80°C);
Lubrication control: Fill 30%-40% of the inner space of the bearing; too much leads to heat; too little leads to dry friction;
Lubrication cycle: Replenish every 2000 hours for high-speed conditions and check every 1000 hours for harsh conditions.
Heat dissipation improvements: Clean motor heat dissipation channels and add heat sinks to bearing end covers; Use non-contact seals for sealing scenarios to reduce heat dissipation hindrance.
3. Shortened lifespan: Material upgrades adapted to working conditions Material upgrade:
High frequency impact, high temperature conditions: Use carburized bearing steel (G20CrNiMo), strength increased by 30%;
High precision and long service life requirements: Use hybrid ceramic bearings (Si3N4 rolling elements), which increase service life by more than 50% compared to ordinary bearings;
New energy vehicle high voltage platform: Use electrically resistant bearings (ceramic rolling elements + insulating coating) to solve the problem of electrical erosion.
Working condition adaptation:
Dusty, humid environment: Replace with double-sealed bearings (2RS + labyrinth seal) to prevent contaminants from entering;
Heavy load scenarios: Replace deep groove ball bearings with tapered roller bearings to increase load capacity 2-3 times.
Conclusion: Precise troubleshooting makes the bearing run more stably for a longer time
Faults in servo motor bearings are not accidental; they are often associated with improper installation, lubrication failure, and incorrect selection. Mastering the entire process of fault type identification - diagnosis - targeted resolution can not only quickly solve the current problem but also avoid potential risks in advance. By optimizing installation, upgrading lubrication, and fitting materials, bearing life can be significantly extended and equipment downtime losses reduced.
