Troubleshooting workflows
Diagnosing a Brake Slip Fault
For maintenance technicians investigating a SRVO-018 Brake abnormal alarm or a BRCH brake check failure that indicates an axis brake is not holding to spec.
- Step 1.
Capture the alarm and symptom
Record the exact alarm (for example SRVO-018 Brake abnormal) or the BRCH result code, which axis and group it applies to, and what the robot was doing at the time.
- Step 2.
Run the BRCH brake check function
Use the documented software brake check (BRCH) function to validate brake holding. The check compares measured holding torque against $BCK_GRP[group].$BRK_TORQUE[axis] for the affected axis and group.
- Step 3.
Confirm the torque threshold against motor specs
Verify $BCK_GRP[group].$BRK_TORQUE[axis] matches the BRAKE SPECIFICATIONS value from the AC SERVO MOTOR manual for the motor installed on that axis. A wrong threshold can cause false pass or false fail results.
- Step 4.
Review BRCH result codes
Interpret BRCH-001 through BRCH-010 results per the documented meanings to narrow the fault to a specific axis and condition before escalating.
- Step 5.
Escalate a confirmed BRCH failure
If BRCH fails or SRVO-018 keeps returning, treat the robot as stop-use and hand the axis off to a qualified technician for inspection and repair per the FANUC service documentation. Don't attempt field-level brake disassembly from this guide.
- Step 6.
Retest after service
After qualified repair, rerun BRCH and clear SRVO-018. Confirm a clean pass on the affected axis before returning the robot to production.
Common questions
- How long does Diagnosing a Brake Slip Fault take?
- Diagnosing a Brake Slip Fault is rated Advanced and takes about 50 minutes across 6 steps.
- What tools do I need?
- You will need Teach pendant, AC servo motor manual with brake specifications.
- What should I do before starting?
- A SRVO-018 Brake abnormal alarm, a BRCH-001 through BRCH-010 result, or another symptom pointing at brake holding capability.
- What is the first step?
- Capture the alarm and symptom. Record the exact alarm (for example SRVO-018 Brake abnormal) or the BRCH result code, which axis and group it applies to, and what the robot was doing at the time.