Before discussing exclusivity, we must define the component.
A Keep Relay (often denoted as K0, K1, K2... up to K999 depending on the control model) is a binary memory bit used within the PMC (Programmable Machine Controller) ladder logic. Unlike standard internal relays that lose their state when power is cycled, Keep Relays are non-volatile. They retain their state (0 or 1) even when the entire machine is shut down.
Think of them as the "dip switches" or "configuration jumpers" of the digital CNC world. They control high-level machine behavior, such as:
The Hierarchy: PMC Ladder → Reads Keep Relay State → Executes Logic → Controls Machine I/O
If a Keep Relay is set to a value the ladder logic does not expect, the machine may not start, an axis may fail to reference, or a tool changer could crash.
For a FANPCNC, Keep Relays are not just parameters—they are the DNA of the machine’s sequence logic. Violating their exclusivity leads to intermittent faults, phantom alarms, and unpredictable safety behavior.
Treat each Keep Relay as if it belongs to a single owner and a single purpose. Document, verify, and protect them. When you respect the exclusive nature of K parameters, your FANUC control will reward you with reliable, repeatable, and predictable machine operation.
Have a conflict story with FANUC Keep Relays? Share it in the documentation log—the machine builder will thank you later.
Fanuc keep relay parameters, denoted by the K address, are non-volatile memory bits used within the Programmable Machine Controller (PMC) to manage machine-specific logic and system configurations. Unlike standard internal relays (R) that reset when power is lost, keep relays retain their state (0 or 1) even after a machine shutdown, making them essential for persistent settings like tool change flags, interlocks, and optional hardware toggles. Core Functions of Keep Relay Parameters
The primary "exclusive" role of keep relays is to act as software-driven switches that bridge the gap between fixed CNC parameters and the machine tool builder's (MTB) custom ladder logic.
Function Toggling: Builders use keep relays to "use or not use" specific machine units, such as enabling/disabling a chip conveyor, high-pressure coolant, or an automatic door. System Configuration: Certain keep relays (specifically
) are reserved for Fanuc system functions, such as enabling ladder editing or controlling how data is backed up to flash memory.
Maintenance & Debugging: For troubleshooting, keep relays can be used to bypass physical sensor alarms or simulate signals (like a "work gap sensor") during machine setup. Address Structure and Bit Significance fanuc keep relay parameters exclusive
Keep relays are organized by address (e.g., K0, K1, K2) and then by individual bits (0 through 7).
K00–K15: Typically reserved for builder-defined machine sequence logic.
K17–K19: Exclusively used for PMC management software data and should not be used for custom machine sequences unless specified by Fanuc.
K900 and above: Often designated as "System Keep Relays" that handle internal CNC-to-PMC communication states. How to Modify Keep Relay Parameters
Changing these parameters requires cautious access to the PMC maintenance screens. Enable Parameter Write (PWE): Set the machine to MDI mode.
Press the [OFFSET/SETTING] key, find the "SETTING" soft key, and change "PARAMETER WRITE" from 0 to 1. Navigate to PMC Maintenance: Press the [SYSTEM] function key.
Select the [PMC] or [PMC MNT] soft key, then navigate to [KEEP RELAY]. Search and Edit:
Key in the desired K-address (e.g., K17) and press [SEARCH].
Move the cursor to the specific bit and enter the new value (0 or 1). Security Measures:
After changes, return the PARAMETER WRITE setting to 0 to prevent accidental modifications. Common Exclusive Use Examples Get to know how to change the Keep Relay!
Fanuc Keep Relay Parameters Exclusive: A Comprehensive Guide
In the world of industrial automation, Fanuc is a well-known and respected brand that provides a wide range of products and solutions for various industries. One of the key aspects of Fanuc's control systems is the use of relay parameters, which play a crucial role in ensuring the smooth operation of machinery and equipment. In this article, we will explore the concept of Fanuc keep relay parameters exclusive, its importance, and how to configure and maintain these parameters. Before discussing exclusivity, we must define the component
What are Relay Parameters?
Relay parameters are a set of values that are used to configure and control the behavior of relays in a Fanuc control system. Relays are electrical devices that are used to switch circuits on and off, and they are commonly used in industrial automation applications to control various types of equipment, such as motors, pumps, and valves. In a Fanuc control system, relay parameters are used to define the characteristics of the relays, such as their timing, logic, and output behavior.
What are Fanuc Keep Relay Parameters Exclusive?
Fanuc keep relay parameters exclusive refers to the ability to maintain the relay parameters in a Fanuc control system, even when the power is turned off or the system is restarted. This means that the relay parameters are retained in memory, allowing the system to resume operation with the same settings as before. This feature is essential in many industrial automation applications, where the settings of the relays need to be maintained consistently over time.
Why are Fanuc Keep Relay Parameters Exclusive Important?
The importance of Fanuc keep relay parameters exclusive cannot be overstated. Here are some reasons why:
How to Configure Fanuc Keep Relay Parameters Exclusive
Configuring Fanuc keep relay parameters exclusive is a straightforward process that can be done using the Fanuc control system's programming software. Here are the general steps:
Best Practices for Maintaining Fanuc Keep Relay Parameters Exclusive
Here are some best practices for maintaining Fanuc keep relay parameters exclusive:
Common Issues with Fanuc Keep Relay Parameters Exclusive
Here are some common issues that may occur with Fanuc keep relay parameters exclusive: The Hierarchy: PMC Ladder → Reads Keep Relay
Troubleshooting Fanuc Keep Relay Parameters Exclusive
If you are experiencing issues with Fanuc keep relay parameters exclusive, here are some troubleshooting steps:
Conclusion
In conclusion, Fanuc keep relay parameters exclusive is a critical feature that ensures the smooth operation of machinery and equipment in industrial automation applications. By maintaining the relay parameters, you can ensure consistency, reduce downtime, and increase safety. By following the best practices outlined in this article, you can ensure that the relay parameters are maintained correctly and that the system operates safely and efficiently. If you are experiencing issues with Fanuc keep relay parameters exclusive, the troubleshooting steps outlined in this article can help you to resolve the issue quickly and efficiently.
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.
Perhaps the most powerful exclusivity of Keep Relays is their role as the customization layer for a mass-produced CNC. Every Fanuc control is a generic computing platform. It is the Keep Relay settings, defined by the machine tool builder (e.g., Haas, Mazak, DMG MORI), that turn this generic controller into a specific lathe, milling center, or press brake.
For instance, two identical Fanuc 0i-MF controls will behave completely differently if their Keep Relays are set differently:
No other parameter type offers this kind of binary, non-volatile, ladder-integrated customization at such a fundamental level. Keep Relays are the exclusive repository for the machine’s "personality"—the choices made by the OEM that distinguish their hardware.
Unlike CNC parameters that directly control numerical values such as feed rates or acceleration curves, Keep Relays are strictly binary (on/off) flags. Their primary and exclusive purpose is to interface with the machine’s PMC (Programmable Machine Controller)—the internal PLC that handles all auxiliary functions like tool changers, coolant pumps, and safety doors.
Each Keep Relay (typically designated as K0.0, K1.2, etc.) is a single bit of memory. When a machine builder writes the ladder logic, they assign these relays to control discrete behaviors. For example:
What makes them exclusive is that they are not readable or writable by the part program (G-code). Standard CNC codes like G10 or system variables cannot modify a Keep Relay. They exist purely for the machine’s internal logic, making them a “private” communication channel between the machine builder and the maintenance engineer, bypassing the operator and the part programmer.