The servo motor in an OTC industrial robot is the core power unit of welding automation equipment, designed for mass production conditions involving continuous arc welding, spot welding, and reciprocating trajectory motion, with stable low speed torque, precise trajectory response, and strong resistance to thermal degradation, supporting high precision positioning and constant load output at welding stations over the long term. Compared with motors used in general purpose handling models, this series of servo motors must continuously accommodate welding thermal cycles, frequent starts and stops, and small positional adjustments. As a result, the wear patterns of the internal windings, bearing assemblies, and encoder sensing structures are more distinctive. The hidden wear caused by long term operation gradually accumulates, resulting in positioning deviations, low speed vibration, abnormal load response, and system alarms. Routine surface level inspections may have difficulty locating the root cause, while a targeted OTC robot repair process can accurately address various electrical, mechanical, and software related faults and restore the motor's original operating performance.
Hidden abnormalities in the motor's electrical circuits are a major cause of frequent errors in OTC robot servo systems. Workshop power fluctuations, high frequency welding interference, and prolonged current impacts can weaken the insulation performance of the motor windings, resulting in reduced turn to turn insulation and unbalanced resistance between phases. These electrical defects do not directly cause shutdown failures, but they can make the motor operating current unstable and dynamic torque output uneven. Minor positioning deviations may then occur during robot welding, and system alerts related to abnormal voltage or current overload may be triggered under certain operating conditions. During the OTC robot repair inspection, the motor should be separated from the mechanical load of the reducer, and the resistance balance of the three phase windings should be tested independently. The phase to phase and phase to ground insulation parameters should be checked to identify fault points with excessive resistance deviation or aged insulation layers, followed by targeted insulation repair and winding reorganization to restore electrical circuit stability.
Encoder sensing faults are a primary source of inaccurate positioning in OTC servo motors. As the motor position signal acquisition unit, the encoder follows the robot arm through high frequency movement for long periods. Its internal sensing chip and signal cable can experience performance degradation and transmission abnormalities, causing counting errors and delayed position feedback. Corresponding equipment errors commonly include abnormal counting and abnormal servo following. Interruptions in signal transmission and reduced sampling accuracy can directly disrupt the robot's trajectory planning logic, causing trajectory drift, joint misalignment, and interruptions during constant speed movement in the welding process. Repair work requires detailed inspection of the encoder supply voltage, signal output waveform, and circuit continuity. Dust and oxidation on the sensor contact surfaces should be removed, and encoder components with degraded performance or distorted signals should be replaced, followed by resetting point data and calibrating the signals.
Wear and failure of the mechanical transmission structure can degrade the motor's operating smoothness and reduce its load capacity. The servo motor output shaft and support bearings are subjected to alternating loads and high frequency start stop impacts from welding equipment over long periods. Bearing grease gradually dries and deteriorates, while the rolling elements and raceways develop superficial wear, causing slight resistance fluctuations during operation. When wear is minor, it may appear only as unsmooth low speed operation. As wear increases, abnormal operating noise and slight shaft looseness may occur, causing overall motor vibration and affecting the smoothness of the welding trajectory. During OTC robot repair, the motor transmission end is disassembled, and dried grease residue and wear debris are removed from the bearing chamber. Bearing rotation smoothness and fit clearance are inspected, and bearing components with excessive wear, binding, or dryness are replaced. A dedicated lubricant suitable for the high speed dynamic operation of servo motors is then replenished to ensure smooth shaft rotation throughout the entire operating range without obstruction.
Abnormal operation of the braking and locking structure can easily cause equipment posture deviation and start stop faults. In OTC servo motors equipped with braking mechanisms, repeated engagement and release of the brake over long periods can cause friction material wear, rebound sticking, and insufficient magnetic attraction. The equipment may be unable to hold its stopped position securely, resulting in slight drift or angular deviation. When welding resumes, the trajectory reference may be misaligned, directly affecting workpiece welding accuracy. Uneven brake clearance and oil or dust adhering to the friction surfaces can also cause jerky starts and stops, motor overload, and heat generation. Repair requires disassembling the brake assembly, cleaning contaminants from the friction surfaces, checking brake pad thickness and the operating condition of the magnetic attraction mechanism, adjusting the brake clearance, and replacing aged or failed brake components to ensure accurate and reliable locking during starts and stops.
Contamination in the cooling system and high temperature degradation can continuously increase the likelihood of various motor faults. Dust, welding fumes, and residue from the welding shop can adhere to the motor cooling air ducts and the cooling ribs on the housing. Long term accumulation can block the cooling passages, preventing heat generated during continuous operation from being dissipated promptly. High temperatures accelerate winding insulation aging, encoder signal drift, and lubricant failure, creating a vicious cycle that substantially shortens servo motor service life. OTC robot repair and maintenance should remove accumulated dust and contaminants from the complete cooling structure, clear blocked areas in the air ducts, and inspect the operating condition of the cooling components to keep the motor temperature controllable during dynamic operation and reduce the effects of high temperature related performance degradation.
After all electrical repairs, mechanical replacements, and structural calibrations are completed, layered operating condition tests should be performed to verify the repair results. First, the individual motor should undergo no load run in to check rotational smoothness, current stability, and signal feedback accuracy, while abnormal noise, vibration, and parameter fluctuations under no load are investigated. The motor should then be installed on the robot body for multi axis coordinated testing covering key conditions such as low speed adjustment, constant speed positioning, and heavy load start stop operation. Trajectory repeatability, load response speed, and system operating parameters should be checked, and any reference deviations introduced by the repair should be corrected. A complete professional OTC robot repair process can address electrical, mechanical, and sensing faults in OTC servo motors, restore the equipment's high precision operating capability, and support the long term stable, accurate, and efficient operation of welding automation production lines.