SRVO-023

Identify the faulting axis

Press RESET on teach pendant, then navigate to MENU → ALARM → F1(DETAIL). Note which axis number is listed in the alarm detail. The alarm will specify the joint (e.g., 'Group:1 Axis:2' indicates J2).

Perform audible brake engagement test

With robot stationary, toggle servo power OFF using the teach pendant (MENUS → SYSTEM → F1[TYPE] → Servo Disconn). Listen closely at the motor of the faulting axis for a distinct mechanical 'click' sound indicating brake engagement. Silence or weak sound indicates brake failure.

J2 and J3 axis brakes are most prone to wear due to constant gravity loading. Brakes typically click within 100-200ms of servo disconnect.

Ensure robot is in a stable position before disabling servo power. Vertical axes may drop if brake is failed.

Verify brake cable continuity and connection

Power down robot completely (PANEL E-STOP + main disconnect). Locate the brake cable connector at the servo amplifier (RDC connector on axis amplifier card) and at the motor connector. Check for loose pins, damaged insulation, or corrosion. Use multimeter to verify continuity from amplifier brake output to motor brake coil (typical resistance 40-120Ω depending on axis).

LOTO required. Brake connector pins can arc if disconnected under power.

Check brake release voltage at motor

Access MENU → SYSTEM → F1[TYPE] → Servo Disconn to monitor brake status. With servo ON, measure DC voltage at motor brake connector (should read amplifier brake voltage, typically 90-180VDC depending on model). Voltage dropout or fluctuation indicates amplifier brake circuit failure or wiring fault.

On R-30iB, brake voltage can be monitored via $BRKVOLT system variable if available on your software version. Compare against nominal spec in mechanical unit documentation.

Inspect mechanical brake assembly

If electrical checks pass, the brake friction disk may be worn, contaminated with oil, or the brake spring may have lost tension. Motor removal and brake disassembly required. Check friction surface for glazing, measure air gap (typically 0.2-0.5mm spec), and inspect for oil contamination from gearbox seal failure.

Axis must be mechanically supported with crane or lift during motor removal to prevent drop.

Verify payload configuration parameters

Navigate to MENU → SETUP → Payload. Verify payload number being used (displayed during program run or set in program header with 'PAYLOAD[n]'). Check configured values against actual tooling weight and CoG offset. Compare total to nameplate rating on J3 arm.

Many integrators never update payload settings from default [1]. Incorrect payload causes both motion instability and stop errors.

Calculate actual payload and moment loading

Physically weigh end-of-arm tooling including all grippers, cameras, cables, and dress-out. Measure center of gravity offset from tool flange using suspension method or CAD. Calculate moment load on J3 axis: M = (payload_kg × distance_from_J3_mm). Compare to specification in mechanical unit maintenance manual.

Include weight of all pneumatic hoses, cable carriers, and fluid lines. These are frequently overlooked and add 5-15kg on large robots.

Review alarm history for pattern analysis

Access MENU → ALARM → F5[HIST]. Review alarm occurrence timestamps and robot positions. If SRVO-023 occurs only at extended reach positions or specific orientations, this confirms gravity/moment overload rather than electrical fault. Alarms occurring at all positions suggest brake or amplifier issue.

Use F4[POSN] in alarm history to see exact robot position when alarm occurred. Extended J3 or horizontal J2 positions increase moment arm significantly.

Test with reduced or removed payload

Remove end-of-arm tooling or reduce to minimum test payload. Re-run motion pattern that triggered alarm. If SRVO-023 clears with reduced payload, overload is confirmed. Solution requires payload reduction, robot upsize, or motion profile optimization to reduce deceleration forces.

Temporary ballast weight can be added to J1 or J2 to test if counterbalancing resolves the issue without payload reduction.

Check DC bus voltage at servo amplifier

Navigate to MENU → SYSTEM → F1[TYPE] → Servo Voltages. Observe DC bus voltage (typically 280-320VDC for R-30iA/iB with 230VAC input, or 560-640VDC for high-voltage systems). Low bus voltage (<270VDC) indicates input power issues, transformer problems, or regeneration circuit faults.

Bus voltage should remain stable under load. Voltage sag >10% during motion indicates undersized supply transformer or line impedance issues.