What causes FANUC alarm 203?

M29 rigid tapping mode commanded but required spindle encoder or position feedback not available. Spindle speed and feed rate combination incompatible for the selected pitch in rigid tapping. Rigid tapping parameter settings incorrect for the spindle configuration. G84/G74 cycle executed without the required M29 mode being active. Spindle not at standstill when rigid tapping mode is initiated.

How do I fix FANUC alarm 203?

1. Verify M29 is commanded before or in the same block as G84/G74 for rigid tapping. 2. Check the spindle encoder is functional — rigid tapping requires spindle position feedback. 3. Verify the feed rate equals spindle speed × pitch (e.g., 1000 RPM × 1.0mm pitch = F1000). 4. Review rigid tapping parameters (5200 series) for correct configuration. 5. Ensure spindle has reached zero speed before activating M29 rigid mode if required.

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FANUC Controller

Program/G-code · Basic · 10-20 minutes

Alarm 203

Fanuc Alarm 203 - PROGRAM MISS AT RIGID TAPPING

Fanuc Alarm 203 occurs during rigid tapping (G84/G74) when the M29 (rigid tap mode) command or spindle speed S command is programmed in an incorrect sequence or position within the tapping cycle. This alarm prevents improper synchronization between spindle rotation and Z-axis feed, which is critical for rigid tapping operations.

FANUCProgram/G-codeBasic10-20 minutes

203

Fanuc Alarm 203 - PROGRAM MISS AT RIGID TAPPING

PROGRAM MISS AT RIGID TAPPING

Root Cause Summary

Fanuc Alarm 203 occurs during rigid tapping (G84/G74) when the M29 (rigid tap mode) command or spindle speed S command is programmed in an incorrect sequence or position within the tapping cycle. This alarm prevents improper synchronization between spindle rotation and Z-axis feed, which is critical for rigid tapping operations.

Causes and Fixes

1
Review the NC program around the alarm occurrence. Verify M29 is programmed in the same block as or before the G84/G74 tapping cycle command (e.g., 'G84 Z-30. R5. F100 M29 S500' or separate preparatory block).
2
Confirm S command (spindle speed) is specified before rigid tapping execution. Check that S value is active and not modal from a previous canceled or interrupted cycle.
3
Verify parameter 5200#0 (G84 type selection) is set correctly: 0=standard rigid tap, 1=high-speed rigid tap. Incorrect setting may cause command sequence interpretation errors.
4
Check parameter 5210 (rigid tapping mode) is set to 1 (rigid tap enabled). If set to 0, M29 commands will be rejected and cause program sequencing errors.

DIY Feasiblehigh confidence

Call a technician if:

·Spindle encoder hardware failure
·Parameter backup/restore needed
·Spindle amplifier replacement required

Prevention

Always use proven rigid tapping program templates
Regularly backup parameter settings
Monitor spindle encoder signals during PM
Use appropriate speeds for tap size and material

Common Mistakes

Programming M29/M30 on wrong lines
Using CSS mode during rigid tapping
Incorrect feed rate calculation for thread pitch
Forgetting to enable rigid tapping in parameters

Related Alarms

202 204 205 410 411

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