Maintenance & Troubleshooting of CNC Robots Flashcards

A FANUC robot joint fails to move and displays SRVO-006 (Hand Broken). In a typical configuration, what triggers this alarm?

Answer: An end-of-arm tooling overload signal or broken-tool detection I/O input is active

SRVO-006 is triggered by an active signal on the configured hand-broken detection I/O input, which is typically wired to a tool crash sensor or pneumatic pressure switch.

When performing FANUC joint mastering using the Master/Cal fixture method, the robot joints must be positioned at:

Answer: The zero-degree reference position defined by the mastering fixture marks

Fixture mastering requires aligning each joint to its physical zero-degree mark (witness line or tooling hole) so the pulse coder reference matches the mechanical zero position.

During FANUC controller maintenance, the technician notices the SRAM battery alarm is active. What is the immediate risk if power is cycled without replacing the battery first?

Answer: All SRAM-stored data (programs, mastering, system variables) will be lost

SRAM is volatile memory backed only by the controller battery; if power is cycled with a dead battery, all programs, mastering data, and system variables stored in SRAM are permanently erased.

A FANUC robot axis moves in the wrong direction compared to taught positions after a motor replacement. The technician should:

Answer: Check and correct the axis direction parameter ($DIR_PARAM) or perform re-mastering

Wrong-direction movement after motor replacement typically indicates the replacement motor has a different encoder phase or the axis direction parameter needs to be verified and corrected, followed by re-mastering.

In FANUC CNC robotics, what is the purpose of the 'Torque Limit' instruction (TL[n]) in a TP program?

Answer: It limits the servo torque to protect workpieces or tooling during specific motion segments

TL[n] temporarily reduces the servo torque output to a percentage of maximum, used to prevent workpiece damage, detect obstructions, or protect tooling during force-sensitive operations.

A FANUC robot's wrist joint (J4/J5/J6) cable unit requires replacement. After the replacement, which additional maintenance task is MANDATORY before returning the robot to production?

Answer: Full TCP (Tool Center Point) calibration and wrist joint mastering

Replacing the wrist cable unit disturbs the wrist joint mechanical assembly, requiring re-mastering of the affected axes and TCP recalibration to ensure positional accuracy.

What FANUC diagnostic utility allows a technician to run a motion test on a single axis without executing a TP program, typically used to isolate servo faults?

Answer: JOG mode with individual joint selection on the teach pendant

Using Jog mode on the teach pendant with JOINT coordinate frame selected allows individual axis motion without a TP program, isolating whether a servo fault is axis-specific.