Fanuc Wn57 Override Function Is Active
Q: Is WN57 the same as EMG (Emergency Stop)? A: No. EMG is a hard stop (red alarm). WN57 is a soft warning (white/yellow message).
Q: Can I disable WN57 permanently? A: Yes, by modifying the PMC message table, but this is extremely dangerous and voids safety certifications. Never do this on a production machine.
Q: Does WN57 appear on FANUC 0i-Mate? A: Yes. The 0i-Mate series (common on lathes and mills) exhibits WN57 identically for Dry Run and Machine Lock functions.
Q: My machine shows WN57 but all switches are off. What now? A: Check for a stuck physical switch (internal contact failure). Use the FANUC diagnostic screen (DIAGNOSIS → PMC → SIGNAL) to see if G104.0 (MLK) reads "1" even when the switch is off. This indicates a hardware failure in the I/O unit.
This article is for informational purposes. Always consult your specific FANUC CNC manual and machine tool builder’s documentation before performing maintenance or altering operational procedures.
The Fanuc message "WN57 OVERRIDE FUNCTION IS ACTIVE" is a PMC (Programmable Machine Control) status message indicating that the machine's signal override feature is currently enabled. This function is primarily used as a debugging tool
by technicians to manually force PMC signals (I/O) during system setup or troubleshooting. While active, it can interfere with the normal logic of the ladder program, which may cause unexpected machine behavior. How to Disable the Message
If the machine has finished being serviced or debugged, you should disable this function to return to standard operation. Use one of the following methods: Via PMC Parameters: Navigate to the PMC Parameter setting screen. Locate the Override Function (often listed as "倍率功能" or "Override Mode"). Move the cursor to the "Valid" setting and change it to Via Keep Relays (K-Address): Change the value of system keep relay Why This Message Appears Active Debugging: fanuc wn57 override function is active
A technician may have left the signal override active after checking the electrical system or I/O signals. Safety Bypass:
In some cases, overrides are used temporarily to bypass interlocks during maintenance (e.g., door interlocks). System Restart Required:
On certain models like the Fanuc 30i/31i/32i, excessive override paths (more than three) may trigger related alarms (like ER47) that require a full CNC restart to clear after settings are adjusted. ladder logic addresses
for a specific Robodrill model to verify which signals are currently being forced?
On a Fanuc system, the message "Override function is active" (often associated with diagnostic or status signals like WN57) is an interesting safety and operational feature primarily designed to manage machine behavior when standard speed or feed constraints are being bypassed. Key Aspects of the Override Active Feature
Operational Awareness: When this function is active, it indicates that the machine's programmed feedrates or spindle speeds are being scaled by a manual selector or a software override. This is critical for operators to know if the machine is running at 100% of its programmed speed or a safer, reduced percentage (e.g., during Manual Handle Feed).
Safety Interlocks: In many Fanuc PMC (Programmable Machine Control) ladder designs, WN57 (or similar window markers) signals that a forced I/O or override mode is engaged. This can be used to prevent the machine from starting a cycle if the override is set too low (stalling the tool) or too high for a specific setup. Q: Is WN57 the same as EMG (Emergency Stop)
Forced I/O Override: In high-end models like the Fanuc 30i/31i/32i Series, an "override mode" for forced I/O allows developers to test machine logic without physical signals. An interesting technical limit is that this mode is typically restricted to three PMC paths simultaneously; exceeding this triggers an ER47 alarm.
Macro Variable Control: Speed and feed overrides can be dynamically disabled or locked via macro variables. If the override is disabled through a macro, the machine ignores the physical dial, which can lead to unpredictable speeds if the operator is not alerted by the "Override Active" status. Common Related Alarms
If the override settings are configured incorrectly or conflict with other system parameters, you might encounter:
ER47: Illegal Override Function Setting (too many PMC paths active).
0011: Feed Zero—occurs if the override dial is at 0% while a cutting command is issued. AI responses may include mistakes. Learn more
WN57 OVERRIDE FUNCTION IS ACTIVE message on a FANUC control indicates that the PMC Override (forced I/O) function is currently enabled
. This is a debugging feature used by technicians to manually force PMC signals during troubleshooting or ladder program setup. This article is for informational purposes
While this function is active, the PMC may not behave as expected during normal machine operation. How to Disable the WN57 Message
To clear this message and return the machine to standard operation, you must turn off the override function: Via PMC Parameters Navigate to the PMC Setting screen on your FANUC control. Find the option for Override Effective Set this value to Restart the CNC to clear the alarm. Via Keep Relay (K-Address) Directly change the keep relay
. This bit typically controls whether the override function is enabled. Why This Happens
This status is often triggered when a user or technician is "forcing" I/O points to test logic without actually firing physical sensors or switches. On newer controls like the Series 30i/31i/32i, an
alarm may also appear if too many PMC paths (more than three) are being overridden simultaneously. Course Hero
In these cases → ignore the warning.
FANUC alarms are categorized by prefixes:
WN57 specifically belongs to a family of safety and interlock warnings. It translates to: “The control is currently in a state where manual or automatic override functions are engaged, preventing the requested action.”