Can Grease Condition Predict Robot Joint Failures? Sampling, Analysis, and Repair Judgment Methods
The color, impurities, and abnormal loss of industrial robot grease can provide clues for diagnosing joint wear, but cannot be used alone as a basis for replacing the reducer. This article introduces grease inspection and fault closed-loop methods for ABB, FANUC, KUKA, YASKAWA, and general-purpose robots.
When industrial robot joints exhibit abnormal noise, temperature rise, or increased backlash, grease condition is an important diagnostic clue. For ABB, FANUC, KUKA, YASKAWA, and general-purpose industrial robots, inspection work should combine operation records, mechanical measurements, and manufacturer maintenance documents, avoiding the determination of reducer damage based solely on grease discoloration.
01. Which Phenomena Require Checking Grease Condition
When the robot exhibits periodic abnormal noise during operation, vibration in specific postures, abnormal trends in joint housing temperature, grease leakage, or decreased repeat positioning performance, a lubrication system inspection can be scheduled. First confirm load, speed, ambient temperature, and collision records, because overload, loose base, abnormal motor brake, and cable interference can also produce similar phenomena.
02. How to Ensure Safety Before Sampling
The equipment should be shut down according to on-site safety procedures, with measures implemented for power-off, pressure relief, and preventing axis drop. Sampling locations, tools, and containers must be kept clean to avoid contamination from dust, cleaning agents, or mixing with different greases. Specific oil draining, grease replenishment, and air bleeding methods, as well as grease specifications, must strictly follow the official manuals for the corresponding brand, model, and axis number; they cannot be applied across different models.
03. What to Focus on When Observing Grease
Record the sample's color, consistency, odor, visible particles, and whether moisture is mixed in, while also checking the discharge port, sealing surfaces, and joint housing. Minor color changes do not equal mechanical failure; if obvious metal particles, abnormal clumping, emulsification, or continuous grease loss are found, further inspection of seals, bearings, gear transmission, and the internal condition of the reducer is necessary. If required, professional institutions can perform wear particle or composition analysis.
04. How to Cross-Reference with Operational Data
Run the robot at low speed under no-load and process load conditions separately, comparing sound, vibration, temperature rise trends, and motor load changes for each axis, and reviewing alarm history. If abnormalities are consistently concentrated in the same joint and at the same angle, continue investigating mechanical clearance, bearings, and internal transmission; if abnormalities change with tool posture or cable bend position, priority should be given to checking the robot body cables, external pipelines, and load settings.
05. How to Verify After Maintenance
After completing grease replenishment, replacement, or component repair, confirm there are no leaks, connections are reset, and safety protections are effective. First perform single-axis testing at a safe speed, then execute combined movements and actual process verification, recording sound, temperature, vibration, load, and repeat operation results. When disassembly involving the reducer, motor, or positional relationships is performed, also check zero points and positioning accuracy according to the manufacturer's procedures.
Proper industrial robot repair should not replace diagnosis with blind part replacement. Incorporating grease samples, alarm logs, and trend data into the robot maintenance archive helps identify early wear and reduce unplanned downtime.
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