What causes FANUC alarm PS025?

Part program contains an illegal or incorrectly formatted command for this alarm type. Missing required address word or parameter value in the program block. Programmed value is outside the allowable range for this function. Conflict between the commanded function and the current modal state. Program post-processor not configured correctly for this Fanuc series.

How do I fix FANUC alarm PS025?

1. Note the block number from the Fanuc alarm screen and locate it in the program. 2. Review the command in that block against the Fanuc programming manual for alarm PS025. 3. Check for missing address words, incorrect values, or conflicting G-code combinations. 4. Verify any required machine options are enabled if using advanced functions. 5. Correct the program and verify before resuming machining.

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FANUC Controller

Program/G-code · Basic · 10-15 minutes

Alarm PS025

Fanuc Alarm PS025 - Spindle Speed Error

Fanuc PS025 alarm occurs when the spindle speed command exceeds allowable limits or contains invalid values during constant surface speed (G96) or direct RPM (G97) mode operation. This typically results from programming errors where calculated or commanded spindle speeds fall outside the range defined by parameters 3741/3742 (minimum clamp) and 3740 (maximum clamp), or when feedrate and diameter calculations in CSS mode generate impossible spindle speed demands.

FANUCProgram/G-codeBasic10-15 minutes

PS025

Fanuc Alarm PS025 - Spindle Speed Error

CIRCLE CUT IN RAPID (F0)

Root Cause Summary

Fanuc PS025 alarm occurs when the spindle speed command exceeds allowable limits or contains invalid values during constant surface speed (G96) or direct RPM (G97) mode operation. This typically results from programming errors where calculated or commanded spindle speeds fall outside the range defined by parameters 3741/3742 (minimum clamp) and 3740 (maximum clamp), or when feedrate and diameter calculations in CSS mode generate impossible spindle speed demands.

Safety

CSS can cause high RPM at small diameters

Causes and Fixes

1
Navigate to SYSTEM > PARAM and check parameter 3740 (maximum spindle speed limit in CSS mode). Verify this value matches your spindle's actual maximum capability and is not set unrealistically low.
2
Check parameters 3741 and 3742 (minimum spindle speed clamp for G96 mode). Ensure minimum clamp is set appropriately to prevent speed from dropping too low during large diameter operations.
3
Review the part program for G96 S___ command value and verify the workpiece diameter at alarm point. Calculate expected RPM using formula: RPM = (S × 1000) / (π × D) where S is surface speed and D is diameter in mm. Confirm result is within parameter limits.
4
Add G50 S____ command in program immediately after G96 to specify an absolute maximum spindle speed override that prevents calculation errors near centerline. Set this below parameter 3740 value as additional protection.

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