In the complex world of Fanuc CNC controls, Keep Relay (K) parameters are essential tools for machine tool builders (MTBs) and maintenance technicians. These non-volatile memory bits are designed to control specific machine behaviors, enable or disable hardware options, and manage complex PLC (Programmable Machine Controller) logic.
The term "exclusive" in the context of Fanuc keep relays typically refers to system-reserved addresses or bits with specific, non-customizable functions that are critical to the CNC's internal operation or safety. Understanding Fanuc Keep Relays
Keep relays differ from standard diagnostic bits because they retain their state—ON (1) or OFF (0)—even after the machine is powered down.
User Keep Relays (K0–K19): These are commonly used by machine builders to define machine-specific options, such as enabling a chip conveyor, bypassing a door interlock for maintenance, or configuring the Automatic Tool Changer (ATC) pattern.
System/Exclusive Keep Relays (K900–K999): These higher-range addresses are often reserved by Fanuc for system-level functions. For example, K928 and K929 may control critical safety circuit interfaces. Unlike user bits, these are often "exclusive" to the system logic and should only be modified under direct manufacturer guidance. Common Uses for Exclusive Logic
While "exclusive" can refer to reserved system addresses, it also describes logic where certain bits are mutually exclusive.
Safety Interlocks: Exclusive bits may ensure that a tool changer and a spindle cannot operate simultaneously.
Machine Options: MTBs often use keep relays to "lock" or "unlock" specific machine features. For instance, K17.1 might be exclusively reserved for maintenance procedures, such as backing up data or resetting turret positions.
Ladder Access: Certain keep relays, like K19, can be used as an exclusive flag to enable ladder editing or internal programmer functions. How to Modify Keep Relay Parameters
Modifying these parameters requires precise steps to bypass the CNC's internal protection. Enable Parameter Write (PWE): Switch the machine to MDI mode.
Press the OFFSET/SETTING key and locate the SETTING soft key.
Change "PARAMETER WRITE" from 0 to 1. The machine will likely trigger an "ALM 100" (Parameter Write Enable) alarm, which is normal during this process. Access the Keep Relay Screen: Press the SYSTEM hard key.
Use the right arrow (expansion) soft keys until you see PMC, then select PMCPRM or PMC MAINTENANCE. Select the KEEPRL soft key to view the bit table. Input the Data: Navigate to the desired address (e.g., K17). Type the new bit value (0 or 1) and press INPUT.
Crucial: Once finished, return to the SETTING screen and change PARAMETER WRITE back to 0. Troubleshooting "Exclusive" Lockouts
If a keep relay refuses to change or reverts after a power cycle, it is often because:
Ladder Logic Coil: The bit is being written to by a "coil" in the PMC ladder logic. In this case, the software overrides any manual changes.
Mode Restrictions: Some machines require the Emergency Stop to be depressed or the PMC to be stopped before certain system bits can be modified. Fanuc PMC - Keep Relays (K Parameter) Explained in English
Keep Relays (K-parameters) are a specialized type of internal memory bit used within the Programmable Machine Control (PMC)
to enable or disable specific machine options, logic flows, or hardware configurations without rewriting the PLC ladder. Key Characteristics of Exclusive Keep Relays Non-volatile Storage:
Unlike standard relays, Keep Relays "keep" their state (1 or 0) even after the machine is powered off. Bit-Level Logic:
They are accessed in the PMC as bits (e.g., K0.0 through K99.7). Option Locking:
OEMs often use specific Keep Relays as "exclusive" switches to toggle between different machine features—such as enabling a 4th axis, switching between manual and automatic tool measurement, or locking out certain door interlocks for maintenance. Safety & Interlocks:
Because they are "exclusive," setting one bit often logically inhibits another operation in the ladder to prevent mechanical collisions or unsafe conditions. How to Access and Modify Keep Relays
To view or change these parameters, follow this standard procedure on most Fanuc controls: Enable Parameter Write (PWE): function key. Set "PARAMETER WRITE" to
(ON). The machine will trigger a non-critical alarm; this is normal MachineMetrics Navigate to PMC Maintenance: function key. soft key, followed by Modify the Bit:
Use the cursor to highlight the specific Keep Relay address (e.g., K0005).
Enter the binary value for the specific bit you wish to change (remembering that bit 0 is on the far right and bit 7 is on the far left). Disable PWE:
Return to the Setting screen and change "PARAMETER WRITE" back to
Always consult your machine's original documentation or the OEM ladder diagram before changing Keep Relays, as they are specific to each machine builder and changing the wrong bit can disable critical safety features or machine functions. common K-relay addresses used by specific manufacturers like Haas or Mori Seiki?
In Fanuc CNC systems, Keep Relays (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
While the term "exclusive" in the context of Fanuc Keep Relays most commonly refers to a bitwise logical operation used within the PMC ladder logic, it can also refer to specific "system" Keep Relays that are reserved for exclusive use by Fanuc or the Machine Tool Builder (OEM). Core Functionality of Keep Relays
Keep Relays are used to toggle machine options and control behavioral logic without changing the core ladder program.
Persistent State: They act as "latching" relays, preserving settings like tool change flags or safety interlocks during power interruptions.
Operational Control: Common uses include enabling/disabling chip conveyors, bypassing faulty sensors for maintenance, and managing turret rotation interlocks.
Address Format: They are defined by a byte address (e.g., K0 to K19) and a bit number (0 to 7), with bits counted from right to left. The "Exclusive" Contexts
Bitwise Exclusive OR (XOR): In PMC maintenance and ladder programming, "exclusive" often refers to the XOR logical process where the bits of one address are compared against another, and the result is stored if they differ. System vs. User Keep Relays:
User Keep Relays (K00–K15): Typically used for machine sequence control defined by the OEM.
System Keep Relays (K16 and above): These are often "exclusive" in that they are reserved for system functions such as keep type memory control or internal programmer functions. For example, K16 is frequently used to manage memory types or ladder editing states. How to Access and Modify Get to know how to change the Keep Relay!
In Fanuc CNC systems, Keep Relays (often referred to as K parameters or K addresses) serve as critical software switches within the Programmable Machine Control (PMC). Unlike standard temporary relays, these are "holding-type" devices stored in non-volatile memory, meaning they retain their state (on or off) even after the machine is powered down. The Role of Keep Relays
Keep relays act as the interface between the machine's hardware and the PLC ladder logic. They are primarily used by Machine Tool Builders (MTBs) to define how a specific machine should behave without requiring a rewrite of the entire ladder program. Common uses include:
Feature Management: Enabling or disabling hardware options like chip conveyors, coolant systems, or specific interlocks.
Maintenance & Debugging: Bypassing faulty sensors (such as a broken conveyor rotation sensor) to keep the machine running during diagnostics.
Process Flags: Tracking ongoing operations, such as signaling that a tool change is in progress so the machine can recover safely after a power failure. Structure and Addressing
Keep relays are organized in an 8-bit octal system, where each address (e.g., K0) contains eight individual bits labeled 0 through 7.
User Keep Relays (K0–K99): Typically reserved for the machine builder to customize operations like chuck clamping or turret rotation.
System Keep Relays (K900–K999): Control internal CNC system functions, such as safety circuit interfaces or ladder editing modes. These are often hidden and only become visible under specific conditions, such as when the emergency stop is pressed. How to Modify Keep Relays
Changing a keep relay is a standard maintenance task, but it requires specific steps to unlock the system's "write" permissions:
Enable Parameter Write: Switch the machine to MDI mode, go to the Setting screen, and change "Parameter Write" from 0 to 1.
Navigate to PMC Maintenance: Press the System key, then use the right-hand arrow soft keys to find PMC Maintenance followed by the Keep Relay soft key.
Locate the Bit: Cursor to the desired address (e.g., K5.4). Remember that bits are counted from right to left (0 is the furthest right).
Input Value: Enter 1 to enable or 0 to disable the function.
Secure the System: Once finished, return to the Setting screen and change "Parameter Write" back to 0 to prevent accidental changes. Implementation Variability
It is vital to note that keep relay assignments are exclusive to each machine builder. For instance, K10.7 might control an air blast on one machine but handle a pallet changer on another. Operators should always consult the specific ladder diagram documentation or the machine's manual before making adjustments. To help you with a specific setup,g., Mori Seiki, Doosan)?
Find the steps to bypass a specific alarm (e.g., door interlock or conveyor)?
Learn how to search the PMC ladder to identify an undocumented keep relay? Fanuc PMC - Keep Relays (K Parameter) Explained in English
Review: FANUC Keep Relay Parameters Exclusive
Introduction
FANUC, a renowned leader in the field of industrial automation and CNC systems, has been continuously innovating to provide robust and efficient solutions for manufacturing processes. One of its significant features in certain models is the ability to keep relay parameters exclusive. This review aims to delve into the specifics of this feature, its implications, benefits, and potential drawbacks.
Understanding Keep Relay Parameters Exclusive In the complex world of Fanuc CNC controls,
In FANUC's CNC systems, parameters are crucial as they define the operational characteristics of the machine. The "keep relay parameters exclusive" feature refers to a setting or function that allows certain parameters related to relay outputs to be preserved or kept unique, even during power cycles or system resets. This ensures that specific configurations or settings for relay outputs are maintained, providing consistency and reliability in the machine's operation.
Benefits
Consistency and Reliability: By keeping relay parameters exclusive, machines can operate consistently, as critical settings are preserved. This is particularly important in manufacturing environments where consistency is key to product quality.
Reduced Downtime: Since specific settings are retained, there's less need for reconfiguration after power outages or system resets, thereby reducing downtime and increasing overall productivity.
Enhanced Control: This feature provides operators with enhanced control over the machine's outputs, allowing for customized operation that meets specific needs or safety requirements.
Simplified Troubleshooting: With known settings consistently applied, troubleshooting becomes more straightforward, as the system's behavior is more predictable.
Potential Drawbacks
Complexity: For users not familiar with FANUC systems or CNC parameter settings, managing exclusive relay parameters can add a layer of complexity to machine operation and maintenance.
Security and Access Control: If not properly secured, the ability to change these parameters could lead to unauthorized alterations, potentially disrupting operations.
Conclusion
The "keep relay parameters exclusive" feature in FANUC's CNC systems represents a valuable tool for ensuring operational consistency, reducing downtime, and enhancing control over machine outputs. While it presents a few challenges, particularly in terms of complexity and security, the benefits it offers make it a significant advantage for industries relying on precise and reliable machinery operations. As FANUC continues to evolve its technologies, features like these will likely play a crucial role in advancing industrial automation.
Rating: 4.5/5
This rating reflects the feature's substantial benefits and its potential to improve operational efficiency, with a slight deduction for the complexity and potential security concerns it may introduce. Overall, it's a powerful feature that, when properly managed, can significantly enhance the performance and reliability of FANUC CNC systems.
In Fanuc CNC systems, Keep Relays (K-parameters) are specific memory addresses that store binary (0 or 1) settings to control machine behavior or enable/disable PLC functions. Unlike standard NC parameters, Keep Relays are often defined by the Machine Tool Builder (MTB)
, meaning their functions are exclusive to the specific machine model or manufacturer. 1. Understanding Exclusive Functions
Because Keep Relays are PLC-based (PMC), they are used to manage functions that are not built directly into the Fanuc software but are instead added by the builder. Customization:
Builders use K-relays to toggle features like tool changers, door interlocks, or coolant options. Non-Volatile:
They are "kept" in memory even when power is turned off, ensuring the machine configuration remains stable. Variable Use:
K0 through K15 are typically reserved for the machine sequence (builder-defined), while K16 and higher are often reserved for system management. 2. Common Keep Relay Examples
While functions vary, many builders follow similar patterns for common machine operations: Typical Function Description Reference Return May force a homing sequence before automatic operation. Door Interlock Enables or bypasses safety door lock signals. ATC Configuration
Selects between different tool changer types (e.g., Rack vs. Umbrella). Spindle Safety
Controls if the spindle can rotate while the door is unlocked. System Access
Often used to enable specialized menus for loading/saving ladder diagrams. 3. How to Modify Keep Relays
To change an exclusive K-relay setting, you must typically follow these steps to unlock the system: Enable PWE: , press the OFFSET/SETTING key, find the "SETTING" soft key, and change PARAMETER WRITE (PWE) from 0 to 1. Navigate to PMC: hard key, then use the right arrow soft keys to find PMC MAINTENANCE Access Keep Relays: Select the KEEP RELAY Edit Values:
Use the cursor to find the target address (e.g., K5.4). Note that bits are read right to left (Bit 0 to Bit 7). Save & Reset:
Change the bit to 1 or 0, then immediately return to the Setting screen to set PWE back to 0 4. Critical Documentation
Because Keep Relay assignments are unique to each builder, you should always consult the following: Machine Builder's Ladder Diagram: Often found in the back of the electrical manual. Maintenance Manual:
Look for the "PMC Parameter List" section specific to your machine's serial number. Ladder Search:
If documentation is missing, you can search for the "K" address directly within the PLC ladder on the CNC screen to see what output it triggers. Fryer Machine Systems How to Enable Parameter Write Enable (PWE) on a Fanuc CNC Consistency and Reliability : By keeping relay parameters
In Fanuc CNC systems, Keep Relays (K-parameters) are software-based latching relays within the Programmable Machine Control (PMC) that maintain their state (ON or OFF) even after the power is cycled. These parameters are primarily used by machine tool builders to enable or disable specific machine options, bypass sensors for maintenance, or configure custom logic without rewriting the entire ladder program. Key Characteristics of Keep Relays
Non-Volatile Memory: Values are stored in non-volatile memory, ensuring that settings like a chip conveyor's "on" status or safety bypasses persist after a restart.
Address Structure: Addresses are typically represented in an 8-bit format (e.g., K0.0 to K0.7). Some ranges are reserved for system functions (often K900+), while others are for machine-specific OEM functions.
Maintenance & Debugging: They are vital for bypassing faulty sensors (like a conveyor rotation sensor) to keep production running while awaiting repairs. Accessing and Modifying Keep Relays
To modify these parameters, you generally need to put the machine in MDI mode and enable "Parameter Write".
Enable Parameter Write: Navigate to the Setting Screen and set PARAMETER WRITE to 1. Navigate to PMC Maintenance: Press the SYSTEM key. Select the PMC soft key. Choose PMCPRM (PMC Parameters) and then KEEP-RL.
Safety Precautions: For certain system keep relays (like K900), values may only be visible or changeable when the Emergency Stop is pressed. Common Applications
Machine Options: Enabling/disabling features like chip conveyors, coolant types, or tool management systems.
Logic Interlocks: Modifying turret rotation requirements (e.g., allowing rotation without requiring the X/Y axes to be at home) to reduce cycle time.
System Controls: Bypassing safety circuit interfaces or hiding specific system screens. Important Documentation
Because keep relay assignments are determined by the Machine Tool Builder (MTB), their functions vary between machines. It is critical to consult the machine’s Ladder Diagram or Maintenance Manual provided by the manufacturer to identify what each specific K-address controls. Fanuc Keep Relay Parameters Overview | PDF - Scribd
Rating: 9/10 for Necessity, 6/10 for User Safety.
The FANUC Keep Relay "Exclusive" concept is a fundamental requirement for modular machine building. It allows a single standard CNC control to adapt to thousands of different machine configurations.
However, FANUC’s interface for these parameters is raw. It lacks a user-friendly GUI or distinct "Read-Only" flags for critical addresses. It puts the burden of integrity squarely on the programmer and the maintenance team.
Recommendation: If you are a machine builder, use exclusive Keep Relays to define hardware existence. If you are a maintenance tech, back up your Keep Relay states before touching them, and treat them like physical DIP switches—do not flip them unless you know exactly what they do.
The second dimension of exclusivity is access. While most CNC parameters can be viewed via the normal "System" or "Parameter" soft keys, Keep Relays are hidden behind a deliberate procedural wall. To view or edit them on a standard Fanuc control (e.g., 0i, 31i), one typically must:
This is not a flaw; it is an exclusive design feature. Fanuc and machine tool builders intentionally sequester Keep Relays because changing them can alter safety logic, bypass limit switches, or fundamentally change the operational sequence of the machine. By making them exclusive to trained service technicians or advanced integrators, Fanuc prevents accidental toggling that could lead to crashes, injury, or non-compliant machine behavior.
If you have lost the password or the OEM is out of business, here are the legal ways to gain exclusive access to Keep Relays:
Never download third-party cracking tools. Illegal modification of safety-related Keep Relays is a violation of OSHA/ISO machinery safety standards.
| Feature | Keep Relays (K) | Data Tables (D) | | :--- | :--- | :--- | | Data Type | Single Bit (0/1) | Multi-bit (Integer/Hex) | | Capacity | Limited (usually a few hundred) | Large (thousands) | | Use Case | Toggle switches, Option bits | Tool offsets, Counters | | Exclusivity | High (often system reserved) | Low (generally open use) | | Speed | Fastest (Bit level) | Slower (Word level) |
Verdict: Use Keep Relays for exclusive "Yes/No" hardware options. Use Data Tables for numerical data or counters.
Problem: A 5-axis Fanuc-controlled router will not complete its automatic tool change (ATC). The arm starts to swing, then stops with a "Cycle Fault" alarm.
Non-Exclusive Approach: The technician guesses the issue, replaces a $1,200 ATC motor, and wastes 4 hours. No change.
Exclusive Keep Relay Approach:
Lesson: The exclusive nature of the keep relay held the exact solution. Without the OEM manual, the parameter is just a random bit.
A common factory mistake is using a "spare" Keep Relay for a new option without checking if the ladder logic already uses that bit elsewhere. Because K parameters are physical addresses, two different subroutines in the PMC cannot safely control the same bit unless explicitly designed for XOR logic.
Exclusive rule: Before assigning a new use to an unused K bit, search the ladder documentation to ensure it is truly unused.
For engineers or maintenance personnel reviewing this feature, here is how to handle Exclusive Keep Relays effectively:
K9.7 is vague; K9.7 (EXCLUSIVE: PALLET CHANGER ENABLED) is clear.