What causes FANUC alarm PS090?

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 PS090?

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 PS090. 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

System · Basic · 5-15 minutes

Alarm PS090

Fanuc Alarm PS090 - Home Position Required

PS090 alarm occurs when the CNC attempts to execute a G-code program or MDI command requiring absolute position knowledge (G90, G54-G59, canned cycles, etc.) before the machine axes have completed reference position return (homing). The control system cannot establish machine coordinate system zero without valid reference position data stored in the position feedback registers.

FANUCSystemBasic5-15 minutes

PS090

Fanuc Alarm PS090 - Home Position Required

REFERENCE RETURN INCOMPLETE

Root Cause Summary

PS090 alarm occurs when the CNC attempts to execute a G-code program or MDI command requiring absolute position knowledge (G90, G54-G59, canned cycles, etc.) before the machine axes have completed reference position return (homing). The control system cannot establish machine coordinate system zero without valid reference position data stored in the position feedback registers.

Safety

Home at reduced speed first time

Causes and Fixes

1
Navigate to POSITION screen (CURRENT > POSITION) and verify 'REF' column shows '0' (not homed) for affected axes instead of '1' (homed).
2
Execute manual reference point return: select MODE to REF (REFERENCE) on machine operator panel, then press +X, +Y, +Z axis direction buttons sequentially to home each axis. Observe dogs/switches trigger and 'REF' indicator changes to '1'.
Ensure axes move in correct direction toward home position. If axis moves away from limit, check parameter 1815 bit settings and reference position direction.
3
Check parameter 1815 (reference position return settings) via SYSTEM > PARAM > [01815]. Verify bit 0 (REP) is set to '1' if reference position check is required, bit 5 (RPS) controls external deceleration dog signal requirement.
4
After successful homing, reset alarm using RESET button and verify DIAGNOSIS screen (SYSTEM > DIAGNOSIS > [#300-#30F]) shows valid absolute position data for all axes.

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