What causes FANUC alarm 027?

G43 or G44 command is programmed without specifying a target axis move in the same block (e.g., G43 H01 with no X, Y, or Z word). Tool length offset Type C is active and two or more axes were commanded in the same G43/G44 block, which is not allowed. A G43/G44 block was written as a standalone line expecting a default axis, but Type C offset requires an explicit single axis. Copy-paste or post-processor error generated a G43/G44 block missing the axis word entirely. Incorrect post-processor configuration outputting G43/G44 in a format intended for Type A/B offset instead of Type C.

How do I fix FANUC alarm 027?

1. Open the part program and search for every G43 and G44 block. Confirm each one contains exactly one axis word (e.g., Z1.0) in the same block. 2. If you find a G43 or G44 block with no axis movement, add the appropriate single axis target to that block (typically the Z-axis approach move). 3. If you find a G43 or G44 block commanding two or more axes at once, split the move so only one axis is in the G43/G44 block and the remaining axes move in a subsequent block. 4. Check parameter 5001 bit 0 (TLC) to confirm the machine is actually set for Type C tool length offset. If Type A or B is intended, the post-processor needs to be corrected to match. 5. After editing the program, run a dry-run or single-block test from the corrected line to verify the alarm clears before resuming normal operation.

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FANUC Controller

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

Alarm 027

Fanuc Alarm 027 - NO AXES COMMANDED IN G43/G44

Fanuc Alarm 027 occurs when G43 or G44 tool length compensation commands are executed without specifying an axis address, or when multiple axes are commanded in the same block with Type C tool length offset active. This alarm is specific to systems configured for Type C tool length compensation (Parameter 5001#2=1), which requires a single axis designation per G43/G44 command.

FANUCProgram/G-codeBasic10-20 minutes

027

Fanuc Alarm 027 - NO AXES COMMANDED IN G43/G44

FANUC ALARM 27

Root Cause Summary

Fanuc Alarm 027 occurs when G43 or G44 tool length compensation commands are executed without specifying an axis address, or when multiple axes are commanded in the same block with Type C tool length offset active. This alarm is specific to systems configured for Type C tool length compensation (Parameter 5001#2=1), which requires a single axis designation per G43/G44 command.

Causes and Fixes

1
Review the NC program line that triggered the alarm. Verify the G43 or G44 block contains an axis address (e.g., G43 Z100.0 H01, not just G43 H01).
2
Check Parameter 5001#2 (TLC) via SYSTEM > PARAM > [#5001]. If bit #2=1, Type C tool length compensation is active and requires axis specification.
3
Correct the NC program by adding the appropriate axis address to the G43/G44 block (typically Z-axis for milling: G43 Z__ H__).
4
Reset the alarm (RESET button), return to program start or safe position, and re-execute the corrected program block.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter changes affect other programs negatively
·OEM-specific parameter restrictions unknown

Prevention

Standardize G43/G44 programming format across all programs
Document parameter #5006 settings in machine setup sheets
Use post-processor verification for tool length compensation syntax

Common Mistakes

Forgetting axis letter after G43/G44 in Type C systems
Copying programs between machines without checking offset type compatibility
Changing parameters without understanding impact on existing programs

Related Alarms

026 028 510 511

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