CLOOS robots are widely used on automated welding lines, where their motors repeatedly start, stop, and make small changes in direction while following welding paths. Load fluctuations continually stress the servo motors’ internal components, making them susceptible to various hidden faults over extended operation. These motors differ significantly from general-purpose industrial servo motors: their rotor dynamic balancing and encoder signal acquisition arrangements are specifically developed for welding conditions. CLOOS robot repair therefore requires more than simply applying general-purpose servo motor repair methods. Potential causes must be investigated individually in light of the robot’s operating characteristics to reduce the likelihood of the same problem recurring after repair.
The first abnormalities noticed by on-site personnel usually involve motion. A single axis may judder while the robot follows a welding path, with the judder becoming more pronounced at low speeds and sometimes accompanied by unusual noise. These symptoms can easily be attributed to gearbox backlash or cable faults. Mechanical clearance adjustments or power cable replacement may then be carried out, only for the problem to recur. Troubleshooting should move beyond a purely mechanical assessment by retrieving the drive’s alarm history and reviewing the motor current traces during operation. If the current fluctuates periodically with angular position, this generally points to an internal motor problem rather than a fault in external transmission components.
External checks before disassembly are essential to reducing diagnostic errors during CLOOS robot repair. First, disconnect the motor power and encoder cables. Use specialized instruments to test winding insulation and measure the resistance of the three-phase windings, comparing the results with the factory-specified ranges. Reduced insulation resistance is usually caused by moisture and dust from welding spatter entering the motor housing, settling on the winding surfaces, and gradually degrading the insulation. Unequal resistance across the three phases indicates an interturn short circuit within the windings. Such faults do not directly trigger a shutdown alarm; instead, abnormalities gradually become apparent as the load increases. Check the encoder signal channels at the same time for intermittent signal loss. Encoder faults can corrupt position data, causing positioning drift and increased error at target positions.
Disassembly should begin only after external electrical tests confirm internal damage to the motor. During CLOOS robot repair, mark the relative positions of components, including the rotor, encoder end cover, and seals, to prevent alignment errors during reassembly. CLOOS welding servo motors have compact sealing arrangements. As sealing rings at the housing joints age under prolonged heat exposure, fumes, dust, and moisture can continually enter the motor cavity and attack the enamel-insulated winding wire. This is also the main cause of interturn short circuits. After removing the rotor, inspect the condition of the bearings. Wear and pitting on the bearing raceways produce periodic noise during rotation and increase resistance to motion, raising the drive’s output current and intensifying winding heating.
Winding repair is the most technically demanding stage of CLOOS robot repair. Control the heating temperature when removing the old windings, as excessive heat can damage the magnetic permeability of the rotor core. Once the core is damaged, the repaired motor’s output characteristics will be permanently degraded. Remove residual insulation from the core slots, install new slot insulation, and arrange the enamel-insulated wire strictly according to the original winding turn count and wire diameter to ensure consistent electrical parameters across all three phases. After winding, impregnate the windings with insulating varnish and cure it. The curing process must produce a complete, dense insulation layer capable of withstanding the workshop’s moisture and dust. Once the varnish has dried, recheck insulation resistance and three-phase DC resistance. Proceed with assembly only when the parameters meet the required standards.
Encoder inspection and repair should be handled as a separate task. The encoder is integrated into a confined space at the rear of the motor. Electromagnetic interference, vibration, and impacts at the welding site can cause scratches on the encoder’s optical grating disk or displacement of the signal read head. Minor contamination on the disk can be removed using dust-free cleaning methods. If the disk is scratched or the internal circuitry is damaged, the encoder assembly must be replaced with a compatible model. Precise angular alignment is essential during encoder installation. Misalignment can directly cause loss of the zero reference, failed robot homing, and persistent path deviation. Once all components have been reassembled during CLOOS robot repair, install new sealing gaskets to restore the housing seal and prevent external contaminants from reentering the motor cavity.
After assembly, the motor must undergo no-load and loaded tests in stages before being returned to production. First, power the motor separately for a no-load rotation test. Check that it rotates smoothly without unusual noise or periodic judder, and monitor the no-load current for stability. Once the no-load test passes, reinstall the motor on the robot axis, calibrate the zero position, and run a basic motion program that moves the axis back and forth at different speeds. Continuously monitor the current and temperature data reported by the drive. During the loaded trial run, simulate the varying loads encountered in welding operations and observe the motor’s temperature rise, checking for overheating, judder, and alarms. The motor may be released for workshop use only after all tests meet the acceptance criteria.
After servo motor repair, provide on-site operation and maintenance personnel with the relevant routine inspection points. Regularly check the condition of the motor housing seals, remove accumulated welding dust from the motor surface, and watch for changes in operating noise and temperature rise. Stop the equipment promptly for inspection if abnormalities are detected. Appropriate on-site protection and periodic inspections can slow seal aging, reduce the entry of fumes, dust, and moisture into the motor, extend servo motor service life, and reduce production interruptions caused by unexpected downtime on automated lines.