What causes FANUC alarm 329?

The finishing profile in the shape program has a valley or bump along the second axis (Z-axis for G71, X-axis for G72) that reverses direction, violating the monotonous movement requirement.. Incorrect coordinate values entered in the profile blocks causing the second axis to go back and forth instead of consistently increasing or decreasing.. A missing or wrong sign on a coordinate value (positive instead of negative or vice versa) that creates an unintended reversal in the profile.. Using incremental coordinates (U/W) with incorrect values that cause the cumulative position to reverse direction along the second axis.. The start point of the finishing shape is not properly set relative to the profile, causing the first move to immediately violate the monotonous direction rule..

How do I fix FANUC alarm 329?

1. Open the shape program referenced by G71 or G72 and list out all the second axis coordinates (Z values for G71, X values for G72) in order from start to finish to visually check if they consistently go in one direction. 2. Check each block in the profile for sign errors or typos on the second axis coordinate. A single wrong value that goes against the overall direction will trigger this alarm. 3. If using incremental programming (W for G71 or U for G72), verify that all incremental values for the second axis have the same sign throughout the profile. Mixed positive and negative values are the most common cause. 4. Sketch or plot the profile on paper using the programmed coordinates to visually confirm the shape makes sense and does not double back on itself along the second axis. 5. If the profile legitimately has a non-monotonous shape such as a groove or undercut, you cannot use G71 or G72 for that section. Break the program into separate cycles or use a different cutting cycle like G73 for irregular shapes. 6. After correcting the profile coordinates, run a dry run or graphics simulation to verify the toolpath looks correct before cutting.

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FANUC Controller

Program/G-code · Intermediate · 20-45 minutes

Alarm 329

Fanuc Alarm 329 - FINISHING SHAPE NOT MONOTONOUS (SECOND AXES)

Alarm 329 occurs when the programmed finishing shape path in a G71 or G72 rough turning cycle violates monotonicity rules for the second axis (typically Z-axis in G71 or X-axis in G72). The finishing contour must move consistently in one direction along the second plane axis without reversing direction, as Fanuc requires a strictly monotonous path for these canned cycles to calculate proper roughing passes.

FANUCProgram/G-codeIntermediate20-45 minutes

329

Fanuc Alarm 329 - FINISHING SHAPE NOT MONOTONOUS (SECOND AXES)

G71/G72 PROFILE NOT MONOTONOUS

Root Cause Summary

Alarm 329 occurs when the programmed finishing shape path in a G71 or G72 rough turning cycle violates monotonicity rules for the second axis (typically Z-axis in G71 or X-axis in G72). The finishing contour must move consistently in one direction along the second plane axis without reversing direction, as Fanuc requires a strictly monotonous path for these canned cycles to calculate proper roughing passes.

Causes and Fixes

1
Review the G71 or G72 finishing shape program block-by-block. For G71 verify Z-axis coordinates are strictly increasing OR strictly decreasing throughout the entire path from start sequence number (Ns) to finish sequence number (Nf). For G72 verify X-axis coordinates follow the same monotonous rule.
2
Check for common violations: undercut features, groove operations, or複雑 contours with pockets that require Z-axis (G71) or X-axis (G72) reversals. These features cannot be included in the G71/G72 finishing path definition and must be programmed separately after the roughing cycle.
3
Correct the program by removing non-monotonous segments from the finishing shape. Relocate undercuts, grooves, or reversal features to separate program blocks executed after the G71/G72 cycle completion using G70 finishing cycle or standard G01/G02/G03 commands.
4
Verify corrections in EDIT mode by stepping through the G71/G72 block. Observe the finishing shape display on the graphics screen (PROGRAM > CHECK or use Graph function) to confirm the second axis path shows no direction reversals.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter modifications required beyond operator authority
·Persistent alarm after program corrections
·Complex part geometry requiring advanced programming consultation

Prevention

Always verify finishing shape monotonic progression during program development
Use graphics simulation to validate G71/G72 cycles before production
Maintain consistent coordinate progression in roughing cycle profiles

Common Mistakes

Copying finishing shapes between different roughing cycle types
Ignoring coordinate sequence when manually programming profiles
Modifying existing programs without checking monotonic requirements

Related Alarms

328 330 331

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