Keep Relays (K Parameters) are non-volatile internal relays within the Programmable Machine Control (PMC) that retain their state (0 or 1) even after the machine is powered down. They are primarily used by Machine Tool Builders (MTBs) to toggle specific options, manage maintenance modes, or bypass safety interlocks without rewriting the PLC ladder logic. Accessing and Modifying Keep Relays
: On some turning centers, changing this can allow the turret to rotate without returning to home position, reducing cycle times.
When we talk about , we are referring to the specific, often system-critical K-bits ( K0.0cap K 0.0 K999.7cap K 999.7
In Fanuc CNC systems, (identified as K parameters ) are non-volatile internal relays within the Programmable Machine Controller (PMC) that retain their state even after the machine is powered off. fanuc keep relay parameters exclusive
Never guess what a keep relay bit does. Fanuc provides the infrastructure, but the Machine Tool Builder decides what bits K00 through K89 control. Look up the specific machine’s electrical manual or PMC parameter list.
Double-check that are set to 1 simultaneously. Step 4: Clear Alarms and Test Return to the OFFSET/SETTING screen. Change PARAMETER WRITE (PWE) back to 0 and press INPUT . Press the RESET key to clear the PWE alarm.
To modify these parameters, you generally need to put the machine in and enable "Parameter Write". Keep Relays (K Parameters) are non-volatile internal relays
Accessing Keep Relays is done through the SYSTEM screen on the FANUC operation panel. The process requires navigating through the PMC maintenance menus. Step-by-Step Access Method on the Machine Operation Panel. Navigate to PMC Maintenance: Press the right arrow button ( →right arrow ) to access the menu until you see [PMC] .
Some Keep Relays are exclusively "write-once" or "latching." For example, a Keep Relay that enables a paid option (like high-speed machining) may be set to 1 by an OEM field engineer and then permanently locked. Even if you try to change it back to 0 , the ladder logic will ignore the change due to a memory-protect key or a secondary hardware dongle.
What are you working on (e.g., 0i-F, 31i-B)? When we talk about , we are referring
Use the cursor keys to find the specific K-address (e.g., K0005). Bits are numbered from left to right. Type the new bit value ( 0 or 1 ) and press INPUT . Reset Safety :
Only modify Keep Relays if you have the exclusive documentation from the machine builder. Changing the wrong bit can disable emergency stop circuits or cause physical damage.
Selecting exclusively between an optical tool setter and a radio-frequency workpiece probe.
This is the biggest downside. Keep Relays are not password-protected by default. If a maintenance technician or curious operator enters the PMC Parameter screen and toggles a Keep Relay, they can instantly change the machine's personality.