What causes FANUC alarm 205?

M29 rigid tapping code is programmed but the PLC ladder logic is not setting the rigid mode DI signal G061.0 high before the G84/G74 block executes. Incorrect program sequence where M29 and G84 are not in the proper order or on separate blocks as required by the control. PLC program has a fault or the M29 macro/sub-program is not correctly interfacing with the PMC to assert the rigid tapping signal. Machine parameter settings for rigid tapping are misconfigured, causing the PMC signal handshake to fail. M29 spindle speed S word is missing or placed incorrectly in the program, preventing the PMC from recognizing the rigid tapping request.

How do I fix FANUC alarm 205?

1. Check the CNC part program and confirm M29 is programmed on its own block before the G84 or G74 block, with the S word specifying spindle speed on the same or prior block. 2. Go to the PMC diagnostic screen and monitor signal G061.0 while the program runs up to the M29 block. Confirm it turns ON after M29 executes and stays ON when G84 is called. 3. If G061.0 never turns ON, check the PMC ladder logic for the M29 function code output and trace why the rigid mode signal is not being set. A PLC programmer or Fanuc service may be needed. 4. Verify Fanuc parameters related to rigid tapping are enabled, specifically check that the rigid tapping option bit is set correctly in the parameter settings for your machine model. 5. Review the machine tool builder manual for the exact required program format for rigid tapping on this specific machine, as some builders require a specific M29 call sequence or custom macro.

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FANUC Controller

Program/G-code · Intermediate · 30-60 minutes

Alarm 205

Fanuc Alarm 205 - RIGID MODE DI SIGNAL OFF

Fanuc Alarm 205 occurs when a rigid tapping cycle (G84/G74) is commanded with M29, but the CNC does not detect the rigid mode DI signal (DGN G061.0) in the ON state. This indicates either the spindle is not capable of rigid tapping, the PMC ladder is not turning on the signal, or parameters are incorrectly configured for rigid tap operation.

FANUCProgram/G-codeIntermediate30-60 minutes

205

Fanuc Alarm 205 - RIGID MODE DI SIGNAL OFF

FANUC ALARM 205

Root Cause Summary

Fanuc Alarm 205 occurs when a rigid tapping cycle (G84/G74) is commanded with M29, but the CNC does not detect the rigid mode DI signal (DGN G061.0) in the ON state. This indicates either the spindle is not capable of rigid tapping, the PMC ladder is not turning on the signal, or parameters are incorrectly configured for rigid tap operation.

Causes and Fixes

1
Navigate to SYSTEM > PMC > DGN and monitor G061.0 signal status. Execute M29 S___ manually and verify G061.0 turns ON.
2
Check PMC ladder for M29 (F-code) processing. Verify ladder logic confirms spindle orientation complete (G008.4 for serial spindle or position coder signal) before setting G061.0 ON.
3
Verify spindle enable signal F001.3 and orientation complete signal are both present. Check interlocks in ladder that may prevent G061.0 from turning ON.
4
If ladder logic is missing or incorrect, modify PMC ladder to set G061.0=1 when M29 is active, spindle is oriented, and encoder feedback is valid. Compile and transfer ladder to CNC.
PMC ladder modification requires backup of existing ladder and machine manufacturer approval.

DIY Feasiblehigh confidence

Call a technician if:

·Spindle drive parameters need modification
·Hardware wiring issues suspected
·Encoder feedback problems detected

Prevention

Always use proper program structure with M29 on separate block
Implement adequate dwell time after rigid mode command
Regular verification of DI signal status during setup

Common Mistakes

Combining M29 with other M codes on same line
Insufficient dwell time after M29
Using M03/M04 between M29 and tapping cycle

Related Alarms

204 206 207

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