FANUC robot controllers provide four startup modes for different maintenance conditions: initialization start, controlled start, cold start, and hot start. Select the mode according to whether the controller must erase configuration, expose protected settings, reset operating state, or preserve the interrupted state.
Compare the Four Startup Modes
| Mode | Primary use | Result |
|---|---|---|
| Initialization start | Main-board replacement or system-software replacement | Deletes programs, restores settings to standard values, and clears the factory-established zero calibration; then enters controlled start automatically. |
| Controlled start | Change normally inaccessible system parameters, read system files, or change robot settings | Opens the controlled-mode maintenance interface. |
| Cold start | Return the controller to an operable state when normal power cycling has not resolved the condition | Resets I/O, terminates program execution, and restores defined operating states. |
| Hot start | Restart while retaining the operating context | Normally retains output states, program state, speed override, and coordinate-system selection. |
Perform an Initialization Start Safely
Initialization start is destructive. Back up the controller before proceeding because this operation clears all programs and configured content, including the zero-calibration values established at the factory. Use it only when the maintenance task requires a clean system state, such as after replacing the system main board or system software.
- Shut down the robot system.
- Hold F1+F5 while powering on the controller to open the boot screen.
- Select the third item, INIT start.
- Confirm the initialization when prompted.
- Wait for initialization to finish. The controller automatically enters controlled start and returns the system to its original state.
Use Controlled Start for System Configuration
Controlled start provides access to system parameters and settings that cannot normally be changed. It also supports reading robot system files and changing robot configuration. From the teach pendant, press FCTN, select Restart, confirm the restart prompt, select Startup Mode, and then select Controlled Start. After startup, select the fourth menu item to enter the parameter-setting interface.
Use this mode when the maintenance objective is configuration access rather than controller-state recovery. The evidence does not identify the fourth menu item's label, so verify its displayed function before changing parameters.
Choose Between Cold Start and Hot Start
Cold start resets robot I/O and other input/output signals, terminates the executing program, returns execution to the beginning of the program, restores the speed override to its initial value, selects the joint coordinate system, and releases the robot lock state. To invoke it during power-up, hold PREV+NEXT, switch on the controller, and select the second configuration-menu item, Cold start. The controller also provides a cold-start path while normally powered, but the available evidence does not define that menu sequence.
Hot start normally preserves digital I/O, analog I/O, robot I/O, and group I/O output states. It also retains the execution state—pausing a program at its current point when applicable—and preserves the speed override and coordinate-system selection. However, after an I/O configuration change or hardware rewiring, the controller resets input and output signal states during hot start for safety. Verify the I/O state before permitting automatic motion; after startup, the interface returns to the screen displayed when restart occurred.
FAQ
Does FANUC initialization start delete robot programs?
Yes. Initialization start deletes all programs, restores configured content to standard values, and clears the factory-established zero calibration. Create a backup before selecting INIT start.
How do I enter FANUC controlled start from the teach pendant?
Press FCTN, select Restart, confirm the prompt, choose Startup Mode, and select Controlled Start. Use the fourth item on the resulting interface to reach parameter settings.
What is the difference between FANUC cold start and hot start?
Cold start resets I/O, ends program execution, returns execution to the program beginning, and restores defined operating states. Hot start normally retains outputs, program position, speed override, and coordinate selection, although I/O configuration or wiring changes cause signal states to reset.
