FANUC Fundamentals of CNC Robotics Operation 5 — Questions and Answers
Question 1: What is the FANUC macro instruction $SHELL_CMD used for in advanced programming?
- Executing operating system shell commands from within a Karel program (Correct answer)
- Defining a custom G-code macro for a connected CNC machine
- Creating a shortcut key on the teach pendant
- Launching a background vision process
Correct answer: Executing operating system shell commands from within a Karel program
$SHELL_CMD allows Karel programs to invoke system-level OS commands on the robot controller.
Question 2: Which joint configuration setting prevents a FANUC robot from flipping its wrist during continuous linear motion?
- Wrist Joint (WJ) flag in the program footer
- SINGULARITY AVOIDANCE enable in motion setup (Correct answer)
- CNT value set to 0 at all waypoints
- TCP speed limit below 500 mm/s
Correct answer: SINGULARITY AVOIDANCE enable in motion setup
Enabling singularity avoidance allows the controller to deviate slightly from the programmed path to prevent J5 near-zero wrist flip.
Question 3: On the FANUC R-30iB+ controller, what does the STATUS indicator light flashing amber (yellow) signify?
- The robot is executing a program normally
- A non-fatal alarm is active but the robot can still run (Correct answer)
- The teach pendant is disconnected
- The E-stop circuit is open
Correct answer: A non-fatal alarm is active but the robot can still run
A flashing amber STATUS light indicates a warning-level alarm that does not prevent motion but should be investigated.
Question 4: What is the correct sequence to perform a cold start on a FANUC robot controller?
- Cycle power while holding PREV + NEXT on the teach pendant (Correct answer)
- Hold F1 + F5 during boot to access the configuration menu
- Set the controller mode switch to COLD then cycle power
- Power off, wait 30 seconds, then power on normally
Correct answer: Cycle power while holding PREV + NEXT on the teach pendant
Holding PREV + NEXT during controller power-up forces a controlled cold start that clears runtime state.
Question 5: Which FANUC feature allows a robot program to be automatically selected and started by an external PLC signal?
- Program Select (RSR or PNS) (Correct answer)
- Auto Mode Override
- Remote Start Interlock
- Scheduled Task Execution
Correct answer: Program Select (RSR or PNS)
RSR (Robot Service Request) and PNS (Program Number Select) allow external devices to select and start TP programs via I/O.
Question 6: In FANUC arc welding applications, what does the 'Arc Start Retry' function do?
- Repeats the entire weld path from the beginning if the arc fails
- Attempts to re-ignite the welding arc a set number of times before faulting (Correct answer)
- Switches to a backup wire feeder on arc loss
- Reverses the robot to the previous waypoint on arc failure
Correct answer: Attempts to re-ignite the welding arc a set number of times before faulting
Arc Start Retry re-attempts arc ignition up to a configured maximum count before triggering an alarm.
Question 7: What does the FANUC Zero Torque Control mode enable during robot operation?
- Forces all joint torques to zero for payload estimation
- Allows the robot arm to be freely back-driven by hand with minimal resistance (Correct answer)
- Disables the brake release interlock for maintenance
- Sets joint speed to zero while keeping servos energized
Correct answer: Allows the robot arm to be freely back-driven by hand with minimal resistance
Zero Torque Control (also called drag-teach or gravity compensation mode) lets an operator manually guide the robot with minimal force.
FANUC Fundamentals of CNC Robotics Operation 5
What is the FANUC macro instruction $SHELL_CMD used for in advanced programming?