FANUC Maintenance & Troubleshooting of CNC Robots 5 — Questions and Answers
Question 1: A FANUC R-30iB robot displays a SRVO-062 (BZAL Alarm) on multiple axes simultaneously after a power outage. What should the technician do first?
- Replace all pulse coders immediately
- Check and replace the controller's SRAM backup battery, then perform mastering (Correct answer)
- Initialize the FROM memory and reload all programs
- Replace the main CPU board
Correct answer: Check and replace the controller's SRAM backup battery, then perform mastering
SRVO-062 BZAL indicates battery alarm on the pulse coder; when multiple axes show this after a power outage, the controller SRAM battery is depleted and must be replaced before mastering is redone.
Question 2: During FANUC robot path verification after maintenance, the robot overshoots target positions consistently on high-speed moves. Which parameter adjustment should the technician investigate first?
- Increase the acceleration time constant (CNT value) in TP programs
- Tune the servo loop gain (KV or KPROP) via FANUC's servo tuning utility (Correct answer)
- Decrease the DCS zone size
- Increase the payload setting to add artificial inertia
Correct answer: Tune the servo loop gain (KV or KPROP) via FANUC's servo tuning utility
Consistent overshoot on fast moves typically indicates servo gain (KV/KPROP) is too high or too low, and the FANUC servo tuning utility allows safe incremental adjustment while monitoring the response.
Question 3: A FANUC Collaborative Robot (CR series) stops unexpectedly in production. After confirming no physical contact occurred, the technician should check which system first?
- The EtherNet/IP scanner for dropped packets
- The Force/Torque sensor calibration and sensitivity threshold settings (Correct answer)
- The pneumatic pressure regulator for the gripper
- The vision system camera exposure settings
Correct answer: The Force/Torque sensor calibration and sensitivity threshold settings
CR-series collaborative robots use integrated force/torque sensing to detect contact; false stops typically result from miscalibrated or overly sensitive thresholds that must be reviewed in the safety configuration.
Question 4: What is the function of the FANUC 'Quick Master' (or Single-Axis Master) procedure?
- Masters all axes simultaneously using a reference fixture
- Re-establishes the reference for a single axis without disturbing others, used after motor/encoder replacement on one joint (Correct answer)
- Performs mastering automatically while the robot runs a test program
- Imports mastering data from a backup file
Correct answer: Re-establishes the reference for a single axis without disturbing others, used after motor/encoder replacement on one joint
Quick Master (Single-Axis Master) allows re-mastering of only the affected joint by positioning it at its reference mark, leaving the other axes' mastering data intact.
Question 5: A FANUC robot's collision detection (SPEED CHECK alarm) triggers repeatedly during a specific TP instruction. The tooling and payload settings are correct. What is the next troubleshooting step?
- Disable collision detection for the entire program
- Increase the collision detection sensitivity level (or adjust the torque model) for that motion segment (Correct answer)
- Reduce the robot speed to 10% permanently
- Replace the servo amplifier for the flagged axis
Correct answer: Increase the collision detection sensitivity level (or adjust the torque model) for that motion segment
If collision detection false-triggers on a specific motion, adjusting the collision detection sensitivity level or refining the torque model for that segment prevents nuisance alarms without disabling safety.
Question 6: In a FANUC CNC robot cell, the Programmable Machine Controller (PMC) ladder logic is used to:
- Store TP program waypoints and positions
- Control I/O interlocks, sequence logic, and interface between the CNC and external machine signals (Correct answer)
- Manage servo amplifier gain tuning parameters
- Configure the teach pendant display layout
Correct answer: Control I/O interlocks, sequence logic, and interface between the CNC and external machine signals
The PMC executes ladder logic to manage I/O sequencing, safety interlocks, and communication handshaking between the robot CNC controller and peripheral machine equipment.
Question 7: After installing a FANUC robot axis servo amplifier replacement, the technician should verify the amplifier's axis assignment by checking:
- The color of the amplifier status LED
- The amplifier's DIP switch or parameter setting that assigns it to the correct axis number (Correct answer)
- The part number printed on the amplifier faceplate only
- The motor nameplate current rating matches the old amplifier
Correct answer: The amplifier's DIP switch or parameter setting that assigns it to the correct axis number
FANUC servo amplifiers use DIP switches or software parameters to define which axis they control; an incorrect assignment will cause the wrong joint to respond, requiring verification before powering up.
FANUC Maintenance & Troubleshooting of CNC Robots 5
A FANUC R-30iB robot displays a SRVO-062 (BZAL Alarm) on multiple axes simultaneously after a power outage.
What should the technician do first?