Spindle Servo Motor Repair
Spindle motor repair naturally compliments servo repair. Spindle motors use servo technology to run closed loop. All considerations for servos apply to spindles, in some respects spindle motor repair can be even more intricate. Spindles endure an intense evaluation specifically tailored to their characteristics. We obtain a comprehensive understanding of the spindle motor’s condition not only to fix what is broken, but also to fine tune the motor for optimum performance. It is our goal to retrofit, repair, or re-manufacture your spindle motor back to “Like New” condition.
Proper spindle motor repair requires specialized knowledge, skills and tooling. It is important for any company that repairs spindle motors to have precision measuring devices to check mechanical tolerances, balance, and feedback signal integrity. Servotech has built relationships with many manufacturers such as Mitsubishi, Yaskawa, Fagor, and Fanuc. These relationships have allowed us to build a vast library of documentation, which we utilize to verify the quality of our repairs.
1. Motor Evaluation
Servotech stringently inspects all electrical and mechanical parts on all spindle motors. During our evaluation, we check for:
- Bearing fits and bearing journals on the rotor
- End-bell cooling jacket integrity
- Flange fits, and mounting surface imperfections
- Broken conduit boxes, compromised terminal blocks
- Worn output shafts, key ways, and pulleys
- Corroded and/or broken flanges
- Flanges suffering from stress fractures
- Winding condition
- Cooling fan condition
Inspection of a spindle rotor with a bad bearing journal, and initial balance reading on a rotor.
2. Repair of Motor Problems
Any defective parts that do not meet factory standards are repaired during the process. Some of our standard procedures include:
- Windings – AC and DC spindle windings are washed, baked, and redundantly tested.
- Re-winding – any windings that are shorted or irreparably contaminated are stripped and rewound in our professional winding department.
- Bearing fits that do not meet tolerances are bored and bushed. Bearing journals are chromed and ground.
- Rotors are balanced by our balancing department specialists to decrease vibration.
- Cooling fans are rebuilt or replaced depending on their condition and availability. Siemens and Mitsubishi spindle motors use a standard cooling fan that is not cost effective to rebuild so Servotech keeps plenty of them in stock.
Servotech stock magnetic proximity sensor and its output, used by many different manufacturers. Pictured: Fanuc
3. Preliminary Testing of Repaired Spindle Motor
Each spindle motor repair will be meggered numerous times. Both electrical and mechanical procedures constitute our battery of tests.
- “Spindle-scope”, an iPad friendly vibration analysis test to identify excessive vibration.
- Test to confirm there are no grounded electrical parts in the spindle motor (Megger test).
- All AC stators are surge tested to at least 1500 volts.
- After the baking process DC armatures go through a bar to bar test. This test will show if there are any shorts or opens in the winding.
- Spindle sensor testing and adjustment. Spindles often utilize proximity sensors that need to be tuned or gapped to very tight tolerances. Fanuc for example uses toothed wheels that need to be gapped just right in order to achieve the proper voltages that the drive will recognize without errors.
A spindle during the repair process with a fan that needs rebuilding, and the final product. Mitsubishi spindle motor.
4. Spindle Assembly
Once the individual components of a spindle have been repaired and tested to our technician’s satisfaction, the motors are rebuilt. The assembly process employs careful handling of delicate parts and often improves internal motor components. Our assembled spindle motors utilize:
- High-speed ceramic bearings – any application that sees high RPM, 8000 or greater, is subject to tremendous forces that can take small imperfections and magnify them. Our bearing choice is as important as our machining skill.
- High speed grease- complimentary to the bearings is good grease, no component of our spindle motors is skimped on. It does not behoove our process or our customers to cut corners, our collection of high speed grease is no exception.
- All new seals, O-rings, gaskets and connectors – ensure that your spindle motor is protected from liquid contamination.
- Two-part epoxy coating for an added protection – the same coating used on Navy submarines.
Spindle motor being run on a factory drive in the final test department, accompanied by a vibration analysis report that was preformed simultaneously.
5. Final Spindle Servo Motor Testing
Once the spindle motor has been re-assembled, it is subjected to final testing. Final testing is its own department at Servotech that re-tests every component of the motor, cooling fan and sensor. The spindle motor is then run on a factory drive. Bearings are worn in properly before the motor is brought up to full RPM. Once the motor has achieved maximum rpm, final vibration analysis is conducted to make sure that the motor will not wear through its components in undo time. Servotech takes pride in the spindle drives it has accrued.
Mitsubishi spindle motors were designed to run on Mitsubishi drives, the same can be said for Fanuc and Yaskawa. Our drive collection is constantly being upgraded and added to, in an effort to stay on top of current technology and to give our final test department the edge it needs to ensure that the repair process was completed correctly.
6. Final Name Plating
Before leaving the shop, Servotech fabricates all new nameplates. Each nameplate is completed with factory data so that the appropriate information is available to the customer when they need it to install their spindle motor. Additionally, we include the Servotech job number that corresponds to the motor paperwork so the repair can be traced and quickly referenced for data and procedures that were conducted.