Fanuc Servo Motors on CNC Machines
Fanuc AC servo motors move each machine axis and send position feedback to the control through a Pulsecoder encoder on the motor. Alpha series motors carry A06B part numbers like A06B-0371 for the Alpha 1/3000 and A06B-0123 for the Alpha 3/3000. Some axis motors add a holding brake on the shaft and an absolute encoder with battery backup for axis position.
Older Fanuc machines run DC servo motors with carbon brushes on the commutator. A DC servo motor rebuild replaces the bearings, the seals, and the carbon brushes. Some rebuilders stock hard-to-find Fanuc OEM parts like seals, encoder covers, and specialty connectors.
Fanuc Servo Motor Repair Shops
Automation & Control Technologies (ACT)
Perrysburg, OH
Brands: Fanuc
CNC Electronics Inc
Charlottesville, VA
Brands: Fanuc
Global Electronic Services
Buford, GA
Brands: Fanuc, Haas, Okuma
Lakeside CNC Electronics
Addison, IL
Brands: Fanuc
MRO Electric and Supply
Raleigh, NC
Brands: Fanuc
Northline Industrial
Redford, MI
Brands: Fanuc, Makino, Okuma
Repair Zone
Bay City, MI
Brands: Fanuc
Servotech, Inc.
Middletown, CT
Brands: Fanuc
T.I.E. Industrial (FanucWorld)
La Vergne, TN
Brands: Fanuc, Okuma
Tri Star CNC Services, LLC
McHenry, IL
Brands: Fanuc
York Repair
Bay City, MI
Brands: Fanuc
Compare Fanuc Servo Motor Repair Shops
This table lists turnaround, warranty, and evaluation terms from each shop's published information.
| Shop | Repair type | Turnaround (business days) | Warranty (months) | Free evaluation | Rush service |
|---|---|---|---|---|---|
| CNC Electronics Inc | Ship-in repair | Not listed | 12 | Not listed | Not listed |
| Global Electronic Services | Ship-in repair | 3-5 | 24 | Yes | Yes |
| Lakeside CNC Electronics | Ship-in repair | 2-3 | 12 | Yes | Yes |
| MRO Electric and Supply | Ship-in repair | 2-3 | 12 | Not listed | Not listed |
| Northline Industrial | Ship-in and on-site | Not listed | 12 | Yes | Not listed |
| Repair Zone | Ship-in repair | Not listed | 12 | Not listed | Yes |
| Servotech, Inc. | Ship-in repair | 5 | 12 | Not listed | Yes |
| T.I.E. Industrial (FanucWorld) | Ship-in repair | Not listed | 12 | Not listed | Not listed |
| Tri Star CNC Services, LLC | Ship-in and on-site | Not listed | 12 | Not listed | Not listed |
Common Servo Motor Failures
Bearing wear in a servo motor shows up as noise from the motor and calls for an evaluation at that stage. A failed bearing can damage other parts of the motor and push the repair cost much higher than a bearing job. Published repair records on Fanuc Alpha motors list bad front and rear bearings along with bent shafts and worn brakes.
Servo motor encoders count as delicate electronic parts and pick up contamination easily. Most encoders run on internal bearings with their own wear life apart from the motor bearings. Coolant or oil inside a motor damages the coil insulation, the bearings, and the encoder.
Motor, Cable, or Amplifier
An excessive position error alarm like SV0411 can trace back to the servo motor encoder or to a break in the cable shield. Serial encoder alarms on Alpha systems can come from a fault on the encoder interface board as well. A check of the feedback cable and connector belongs ahead of any motor removal and saves a trip for a good motor.
Some axis symptoms overlap between servo motor faults and mechanical wear in the ball screw on the same axis. Following error alarms show up with a worn ball screw as well as with a failing motor encoder. A check of the mechanical side first keeps a good motor off the repair bench and points the work at the right part.
What a Servo Motor Rebuild Covers
A servo motor rebuild starts with a full teardown and an inspection of each part for wear, damage, and contamination. Some rebuilders then wash and bake the motor to clear out contaminants. Rebuilders replace all bearings and seals and machine the shaft or end bells in cases of wear or damage.
Encoder work comes next and calls for special equipment to align the encoder to the motor poles. Encoder repair can include cleaning, optical alignment, and new encoder bearings ahead of reinstallation on the motor. Reassembly ends with checks on encoder alignment, brake torque, and shaft runout against the OEM specs for that motor.
Testing After the Rebuild
Post-rebuild testing checks motor function, the brake, the encoder, and the thermistors. Test stands measure EMF, encoder or resolver feedback, and commutation alignment ahead of production use. Rebuilders compare those readings against the manufacturer data sheets for that motor model.
Run testing commissions the motor on a servo amplifier and turns the motor forward and reverse for an hour or more. Some shops run the motor through a full CNC simulation for two hours to check performance against OEM specs. Other shops test each motor under load in custom simulators set up to replicate real working conditions.