✅ Rapid traverse override set to 100% when parameter has flagged that as “override active”
✅ Feed override knob set above 100% (if parameter enabled)
✅ Manual handle override (jog/handle multiplier in effect)
✅ Programmed override via PMC or G-code (e.g., G10.6 or G10.9 on some controls)
✅ Dry run + feed override combination tripping a builder-defined warning
✅ Machine builder’s custom PMC logic activates WN57 when any override ≠ 100%
For maintenance engineers and integrators, understanding why WN57 triggers requires a look at the PMC (Programmable Machine Controller) ladder logic.
WN57 is not generated by the CNC core itself; it is generated by the PMC based on specific diagnostic signals. The CNC sends a "mode change request" to the PMC. The PMC checks the following signals (typical addresses – confirm against your ladder diagram):
| Function | FANUC Signal Name | Typical Address | | :--- | :--- | :--- | | Machine Lock 1 | G104.0 | G116.0 (older) | | Dry Run | G104.7 | G116.7 | | Aux Funct Lock | G104.1 | N/A | | Handle Interrupt Mode | Input from rotary switch | Varies |
If any of these signals are "1" (active) and you attempt to transition from STOP to START or EDIT to MEM, the PMC explicitly sets the WN57 message in the message table (address range: 3000-4000 in the message list).
What it is:
The WN57 alarm (or status message) on a FANUC CNC control indicates that an override function is currently enabled – typically a rapid traverse override, feed rate override, or a dry run override. Unlike many alarms, WN57 is generally an informational message, not a critical error. The machine will continue to run, but with altered motion parameters.
When it appears:
Key implications:
Useful tips for operators:
Pros of having this message:
Cons / annoyances:
Final verdict:
A useful safety reminder, not a problem. Treat it as a “heads-up” that the machine is not running exactly as programmed. Always check it before running production.
If you need help disabling a specific override or understanding a custom ladder message related to WN57, let me know your FANUC control model (e.g., 0i-MF, 31i, 18i).
WN57: OVERRIDE FUNCTION IS ACTIVE is a PMC (Programmable Machine Control) warning indicating that the ladder program's "override" or "forced I/O" function is currently enabled.
This function is primarily used during debugging to force specific signals manually. To clear the warning, you must disable the override mode within the PMC parameters. Cause of the Alarm The alarm is triggered when the Override Mode
for PMC paths is active. This state is often left on accidentally after troubleshooting or machine setup. While active, the system may prevent the ladder program from executing correctly or may result in an
error if too many paths (typically four or more) are being overridden simultaneously. Course Hero Recovery Steps
To resolve this warning and return the machine to standard operating mode, follow these steps: Locate PMC Parameters : Navigate to the PMC Parameter settings screen on your controller. Disable Override : Find the Override Function
(often labeled as "Override Effective" or similar) and change its setting to "Inactive" Direct Parameter Change
: Alternatively, you can directly change the system K-address to disable the function.
: Once the setting is changed, restart the CNC to clear the warning message. Important Safety Note:
Ensure all maintenance or debugging tasks are complete before disabling this function, as it may impact signal monitoring used during setup. for other PMC signals on your Fanuc Controller
The WN57 "Override Function is Active" is a FANUC PMC (Programmable Machine Control) alarm message indicating that the system's "Override" or "Force" function is currently enabled. fanuc wn57 override function is active
While the term "override" usually refers to physical knobs for feed or speed on a CNC panel, this specific WN57 message refers to a PMC software debugging tool. What WN57 Means
In FANUC systems, the PMC Override function allows a technician or programmer to manually force specific signals (inputs or outputs) to a desired state, regardless of the actual logic or physical sensor status.
Purpose: It is primarily used during machine commissioning or troubleshooting to simulate signals or bypass certain interlocks to test ladder logic.
The Message: WN57 is a warning rather than a critical system fault. It informs the operator that the machine logic is not running in its standard state because at least one signal is being artificially held or "overridden." Why It Stays Active
The message persists as a safety precaution. If this function is left active after maintenance: The machine may behave unpredictably. Safety interlocks might be bypassed.
Standard PMC ladder logic operations may be ignored in favor of the manual "force." How to Resolve the WN57 Warning
To clear the WN57 message and return the PMC to normal operation, you must disable the override status in the system settings:
Locate PMC Settings: Navigate to the PMC or SYSTEM menu on your controller.
Access PMC Parameters: Find the [PMC Parameter] or [PMC Config] screen.
Disable Override: Look for an option labeled Override or Override Effective. Use the cursor to change this setting from "Yes" to "No".
Check Keep Relays (K-Addresses): In many systems, this function is tied to a specific keep relay. Setting K906.0 to "0" will often immediately deactivate the override function and clear the WN57 message.
Caution: Before turning off the override, ensure that any forced signals were not masking a physical fault or sensor failure, as the machine will immediately return to following the actual physical inputs.
The red LED on the control panel blinked incessantly, a silent scream in the otherwise quiet machine shop.
Elias wiped grease from his forehead with the back of a hand, leaving a dark smear. He stared at the Fanuc Series 0i-TF screen. The machine, a battered but reliable Okuma lathe they called "Old Bess," had stopped mid-cut.
On the display, in crisp, alarming green text, sat the message: WN57: OVERRIDE FUNCTION IS ACTIVE.
"Come on, Bess," Elias muttered. "Not today. We got a truck leaving at four."
He pressed the Reset button. The message flickered, held for a second, and reappeared. The spindle sat locked. The axis motors hummed a low, waiting tone, but the G-code execution was paused. The machine was effectively saying, I’m not moving until you look at what I’m seeing.
Elias sighed, grabbing his worn Fanuc manual from the toolbox. He knew WN57 wasn't a fatal crash. It wasn't a servo alarm or a blown fuse. It was a warning—a logic gate. It meant a safety interlock had been tripped, usually by the operator trying to speed things up or bypass a step in a rigid tapping cycle.
He toggled the Mode switch to MDI (Manual Data Input). He typed in a simple command to index the turret.
WN57: OVERRIDE FUNCTION IS ACTIVE.
"She’s stubborn today," said a voice from behind.
Elias turned to see Marcus, the shop foreman, leaning against a pillar, sipping coffee. "She’s not stubborn, she’s confused. I didn't touch the override knob. I was running at 100% feed." ✅ Rapid traverse override set to 100% when
Marcus walked over, his eyes scanning the messy control panel. "Check the parameters. Maybe someone messed with the skip blocks."
Elias keyed into the Parameter screen, navigating to the diagnostics. He was looking for the system bits that controlled feed hold and override signals. To a novice, the screen was a wall of binary noise—zeros and ones in rows. To Elias, it was a heartbeat.
He found the bit. Signal G008.6: Spindle Override Active.
"See?" Elias pointed. "The computer thinks I’m holding down the override button. But look." He spun the physical override dial on the panel back and forth. The on-screen percentage readout tracked it perfectly. 50%. 100%. 150%. It should have been clear.
"It’s ghosting," Marcus said. "Loose wire in the back. Probably the vibration from that heavy roughing cut you took earlier."
"Great," Elias groaned. He didn't have time to pull the back panel off and check the terminal blocks. The part was a titanium aerospace bracket; one wrong move and the tool would snap, costing them three hours of re-tooling.
He tapped the Diagnostic soft key again. The WN57 alarm was a "Watchdog" type. It meant the PLC (Programmable Logic Controller) was waiting for a specific condition to go low before it allowed the CNC to proceed. Usually, clearing an override alarm was simple: return the dial to 100% and hit Cycle Start.
Elias did exactly that. He checked the dial. It sat perfectly at the detent for 100%. He hit Cycle Start.
The spindle ramped up, the tool moved forward... and stopped instantly. The red LED flashed.
WN57: OVERRIDE FUNCTION IS ACTIVE.
"She’s really not liking it," Elias said, frustration creeping into his voice. "It’s like the system thinks the dial is stuck at zero, even though the screen says 100%."
"Maybe it's not the dial," Marcus suggested, setting his coffee down. He pointed to a small, unassuming button on the lower right of the panel, partially obscured by a chip guard. "Check the Dry Run switch."
Elias blinked. He reached over and toggled the Dry Run switch on, then off. It clicked firmly.
"Wait," Elias whispered. He looked at the G-code program currently loaded. It was a complex macro program imported from the main office. It used G31 (Skip Function) probes.
He scrolled through the code on the screen.
N50 G31 Z-2. F100.
N60 WN57...
"Wait a second," Elias muttered. "The alarm isn't hardware. It's in the program."
He scrolled up to the header variables. The programmer had inserted a safety logic check. It was looking for a specific input state. If the machine detected any external override signal—like a feed hold or a dry run active—during the probing cycle, it triggered a user-defined macro alarm (WN57) to prevent the probe from crashing into the part due to incorrect feed
The message "WN57 OVERRIDE FUNCTION IS ACTIVE" is a specific Programmable Machine Control (PMC) alarm found on Fanuc systems, indicating that the system's "Override Function" (倍率功能) has been enabled.
This is not typically a mechanical failure but a status alert informing you that the PMC is currently in a debugging or forced state. Core Meaning of WN57
The WN57 alarm appears when the PMC Override feature is active. This tool is primarily used by developers or maintenance technicians during the debugging process to:
Force PMC signals to specific states regardless of physical I/O conditions.
Test logic within the PMC program without needing the actual machine hardware to be in a specific position. Key implications:
Bypass certain interlocks temporarily to verify program flow. Why It Needs to Be Deactivated
While useful for testing, this function should be disabled once debugging is complete. If left active, it can:
Prevent normal operation: Forced signals may prevent the PMC from responding to real sensors or operator inputs.
Create safety risks: Crucial safety interlocks might be bypassed or ignored by the forced logic. How to Resolve the Alarm
To clear the WN57 message, you must disable the override function through the system parameters or the PMC maintenance screen: Via PMC Parameters: Navigate to the PMC Parameter Setting screen. Locate the Override Function (倍率功能) option. Change the setting from "Effective/Yes" to "No". Via Keep Relays (K-Addresses):
The override function is directly linked to the system address K906.0.
Setting K906.0 to 0 will immediately deactivate the function and clear the WN57 alarm after a system restart.
Are you currently debugging a new PMC ladder, or did this alarm appear unexpectedly on a machine that was previously running?
Understanding the FANUC WN57 Override Function Active Message
The message "WN57 OVERRIDE FUNCTION IS ACTIVE" is a PMC (Programmable Machine Control) alarm commonly found on FANUC CNC systems. Unlike standard system alarms that indicate hardware failures, this message signifies that a specific PMC debugging tool—the Override Function—has been enabled.
This function is typically used by technicians and builders during machine commissioning or ladder logic debugging to manually force or "override" PMC signals. When active, it can prevent the PMC program from operating normally, which is why the control displays this warning message. Why the WN57 Message Appears
The "Override Function" allows an operator or technician to force a signal in the PMC ladder to a specific state (ON or OFF), regardless of the actual logic or physical input. This is useful for:
Testing Interlocks: Checking if a tool changer will move even if a specific sensor isn't triggered.
Debugging Logic: Isolating specific parts of the PMC ladder to see how the rest of the program reacts.
Temporary Bypasses: Allowing the machine to function temporarily while waiting for a replacement sensor.
If you see the WN57 message during normal production, it means this "force" mode was left on, which may cause the machine to ignore safety interlocks or standard operating conditions. How to Deactivate the WN57 Override
To clear the WN57 message and return the PMC to its normal state, you must disable the override effective setting in the system parameters. Method 1: Via the PMC Parameter Screen Navigate to the [PMC] screen on your FANUC controller. Select the [PMCPRM] (PMC Parameter) softkey. Look for the [SETTING] or [OVERRIDE] tab.
Find the field labeled "OVERRIDE EFFECTIVE" (or similar terminology). Move the cursor to this option and set it to "NO" or "0".
The WN57 message should disappear from the alarm screen immediately. Method 2: Via Keep Relay (K-Address)
On many FANUC models, this function is directly tied to a specific Keep Relay. Locate Keep Relay K906.0. Change the bit value from 1 (Active) to 0 (Inactive). Restart the system if necessary to clear the message. Precautions
Because the override function can bypass critical safety logic, it should only be used by qualified maintenance personnel. Always ensure that all "forced" signals are released before returning the machine to automatic production mode to avoid mechanical crashes or operator injury. 【报警】FANUC PMC"WN57 OVERRIDE FUNCTION IS ACTIVE"
This message—"WN57 OVERRIDE FUNCTION IS ACTIVE"—appears on FANUC CNC controls (often on series like 0i, 30i, 31i, 32i, or 21i) when the control is operating in a special override mode that bypasses certain safety or standard operating limits.
Below is a practical operator & setup guide to understanding, handling, and clearing this condition.
