Troubleshooting workflows
Diagnosing a FANUC Robot That Stalls Mid-Program
Work through the common causes when a FANUC R-30iB robot halts partway through a program without a clear alarm, from wait conditions to I/O and sensor faults.
Identify the exact stall point
Note the line or instruction where the robot stops and whether any alarm or message accompanies it.
Check for a wait condition
Review whether the program is waiting on an input signal, such as a part-present sensor or a downstream machine ready signal, that has not changed state.
Check the actual I/O status
Look at the live I/O screen to see whether the expected signal is present, and trace back to the originating device if it is not.
Inspect the originating sensor or device
Check the sensor, PLC output, or upstream equipment responsible for the signal the robot is waiting on.
Check for a timeout setting
Confirm whether the program has a timeout on the wait instruction and whether it is set appropriately for the process.
Review recent program or cell changes
Check whether a recent change to the program, PLC logic, or upstream equipment could explain why the expected signal is no longer arriving.
Correct the root cause
Repair the sensor or device, correct the PLC logic, or adjust the timeout as appropriate once the cause is identified.
Run a full cycle test
Execute several complete cycles to confirm the stall does not recur before returning the cell to unattended production.
Common questions
- How long does this procedure take?
- Diagnosing a FANUC Robot That Stalls Mid-Program is rated Intermediate and takes about 45 minutes across 8 steps.
- What tools do I need?
- You will need Teach pendant, I/O status screen, Program listing for the affected routine.
- What should I do before starting?
- Point in the program where the stall occurs identified.
- What is the first step?
- Identify the exact stall point. Note the line or instruction where the robot stops and whether any alarm or message accompanies it.