Fanuc Wn57 Override Function Is Active [patched] Now

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.

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. fanuc wn57 override function is active

Are you currently debugging a new PMC ladder, or did this alarm appear unexpectedly on a machine that was previously running?

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." The message "WN57 OVERRIDE FUNCTION IS ACTIVE" is

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%." Step 1: Read the Operator Panel – Physical

"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

Here’s a useful, practical review of the "FANUC WN57 Override Function is Active" message, written for CNC operators and setup personnel.

Step 1: Read the Operator Panel – Physical Switches

Do not rely solely on the CRT/LCD screen. Look at the physical operator panel.

• Dry Run: Is the LED lit or the switch engaged? Turn it OFF.
• Machine Lock: Is the green LED for "MLK" on? Turn it OFF.
• Single Block: Is the "SBK" light on? Press it once to deactivate.
• Aux Lock: Look for buttons labeled "MST LOCK" or "AUX LOCK." Disable them.

Why does the machine builder use WN57?

Safety. If Machine Lock is on, the position display moves, but the actual table does not. Running a program normally would crash the tool. WN57 is a prevention alarm, not an error. It forces the operator to consciously acknowledge the override condition.

Scenario 2: The Block Search Aftermath

After performing a Block Search (mid-program start), the operator may not complete the "distance-to-go" cancellation. The controller remains in an “Override” state (a type of position deviation allowance) until the cycle start is pressed again. Attempting to edit or reset the sequence prematurely triggers WN57.