Timeline Errors#

Overview#

When a change makes an earlier feature produce geometry that a later feature cannot use, the later feature fails. Fusion marks it in the timeline:

• Warning (yellow highlight): per Autodesk's Compute All help, a parameter, feature or assembly relationship that cannot be computed is highlighted yellow (warning) in the timeline.
• Error (red highlight): the same, highlighted red. Features that depend on a failed feature are typically affected too.

A single root failure often produces a long red chain downstream. The skill is finding the first failing feature and fixing that one.

Typical causes:

• A sketch lost a profile or dimension, so an extrude has no closed profile.
• A face or edge that a fillet, shell or hole referenced no longer exists or was split/merged.
• A dimension or parameter value made the geometry impossible (negative length, fillet larger than the face, wall thicker than the part).
• A referenced component, joint or projected geometry was deleted.
• A derived or linked source changed and no longer contains what the dependent feature needs.
• A parameter expression is invalid (unit mismatch, divide by zero).

Where to find it#

• Timeline: features highlighted yellow (warning) or red (error). Right-click the feature and choose Review Warning; the warning or error message appears in the lower-right of the window. Expand it and try any advice it gives.
• Feature dialog: double-click the failing feature to edit it and reselect any missing geometry.
• Change Parameters dialog: check parameter expressions for syntax or unit problems.
• Compute All: Modify > Compute All or Ctrl+B recomputes everything and shows what still fails.

Step by step#

The standard repair routine#

1. Stop and do not click randomly. Note the first red icon from the left. Everything after it is probably collateral.
2. Right-click it and choose Review Warning, then read the message. Autodesk suggests: edit the feature, reselect any missing geometry, and identify upstream features that are referenced downstream and may have been modified, suppressed or deleted.
3. Drag the Timeline Marker to just before the first failing feature. If the model looks right there, the problem is in that feature or the changes that fed it.
4. Double-click the failing feature. Look for empty selection boxes. Reselect the faces, edges or profiles.
5. If the inputs look fine but values are impossible, adjust them: smaller fillet, thinner wall, different distance.
6. Click OK and roll forward. Repeat from step 1 if new errors appear.
7. If it still fails, Compute All (Modify > Compute All or Ctrl+B) to recompute everything.

Repair a lost sketch reference#

1. Edit the broken sketch. Look for dimensions or constraints whose geometry has gone, and for projected geometry that no longer exists.
2. Delete the dangling dimension, or re-project the geometry (Project) from a surviving face or edge.
3. Re-add the intended constraint.
4. Finish the sketch; check the downstream feature.

Repair a broken fillet or shell#

1. Edit the feature. The edge/face set may be empty or incomplete.
2. Reselect what you want. If the edges changed, selecting a face fillets all edges of that face, and the fillet tool's Tangent Chain option (see the fillet help) can extend a selection.
3. If the radius is too large for the geometry, lower it temporarily to confirm that is the problem.

Isolate with suppress#

1. Suppress suspect features, one at a time, starting with the first red one.
2. If suppressing clears the following errors, the suppressed feature is the culprit (or its inputs).
3. Unsuppress and fix its inputs, or leave it suppressed if you no longer need it.

Delete versus repair#

If a feature can no longer serve its purpose (the face it fillets is gone), delete it and recreate it later, rather than forcing the old one to work.

Options reference#

Tips and pitfalls#

Tip: Work from left to right. Never fix errors on the right while an earlier error remains; the right ones may disappear by themselves.

Tip: Use Undo immediately when a change creates a cascade. Then make a smaller change, or restructure first.

Tip: Save a version before large edits. The History dialog's saved versions are a safety net the timeline cannot give you.

Warning: Fusion sometimes re-attaches references to the wrong face or edge silently (this is called topological naming ambiguity in CAD generally). A model with no red icons can still be wrong. Always visually check key features after large changes.

Warning: Deleting a feature to "make red go away" can break the features that depend on it. Suppress first to see the effect.

Preventing errors is cheaper than fixing them:

• Reference origin planes and construction geometry rather than faces you may later delete.
• Fully constrain sketches so changes move predictably.
• Avoid filleting or chamfering early; add them last.
• Keep sketches simple: one purpose each.
• Use user parameters with sensible limits, for example wall thickness is less than half of width.
• Build assemblies with joints to origins of components, not to faces that change.

Handling "stale" or odd states#

• If the canvas looks wrong but the timeline looks fine, try Compute All.
• If a feature will not edit, check whether you are rolled back or in a read-only linked component.
• If errors only appear after reopening, check missing referenced files (derived or external references) and update them.

When to give up and rebuild#

If the first failing feature is early and many things depend on it, consider rebuilding that portion in a clean, parameter-driven way. It is usually faster than patching, and you get a better model.

Reading a failure properly#

An error is a message about the first failing feature, so locate it before anything else. Work from left to right and ignore errors to the right until the earliest one is fixed.

A worked failure with numbers#

Illustrative numbers (not Autodesk data): a 60 x 40 x 20 mm box has a 2 mm shell (open top), then a 3 mm fillet on the top rim edges, then a pattern of four 5 mm holes 8 mm from each edge.

1. You change the base width from 40 to 12 mm. The shell still works (12 - 2 x 2 = 8 mm interior). The top-rim fillet of 3 mm needs a rim face at least 2 mm wide plus margin; the rim is exactly 2 mm wide (wall thickness), so a 3 mm fillet exceeds it and the fillet is expected to fail (a radius larger than the geometry allows).
2. The hole pattern also fails, because 8 mm from the edge lands on the opposite wall of a 12 mm wide box (2 x 8 = 16 > 12).
3. Only the fillet is the root cause for the first fix; the hole pattern was an independent second failure. Fix the fillet by lowering the radius to 0.9 mm (below half the 2 mm rim), then deal with the holes by making the edge offset min(8 mm; width / 4).

The lesson: two failures can share a trigger but not a cause, so do not assume a single root.

Message vocabulary#

Note: Autodesk's documentation does not list exact message texts, so rely on Review Warning and the pattern rather than on specific wording.

A repeatable debugging procedure#

1. Save a version (or copy the file) before changing anything.
2. Identify the first red or yellow icon from the left.
3. Binary search: drag the marker to the middle of the suspect range. If the model is fine there, the fault is to the right; otherwise to the left. In a 64-entry timeline, six moves find the first bad feature.
4. Open the feature. For each selection field note whether it is empty. For each number, ask whether it is physically possible (positive, less than half the smallest dimension for fillets and shells).
5. Change one thing and click OK. Roll forward. Repeat.
6. After the repair, stress-test: put the parameter back to its failing value and nudge it up in steps to find the boundary (in this illustrative case, try values around half the rim width and record where it stops working).

Why topology changes break references#

Fillets, chamfers, shells and holes remember faces and edges. When an upstream change splits, merges or deletes a face, the saved reference may not match anymore. Fusion may silently attach to a different face, which is why an error-free model can still be wrong. After large edits, check: hole positions, fillet continuity, thickness of shelled walls (Section Analysis), and symmetry. For design-for-change guidance see the Design-for-change patterns page.

Constraints and sketches in errors#

• A sketch that was fully constrained can become over-constrained after a parameter change makes two relationships conflict. Delete the conflicting constraint, not the dimension.
• A projected edge that disappears turns its sketch geometry into floating geometry; re-project from a surviving feature or origin plane.
• A sketch plane tied to a face that moved should be reattached to a construction plane.

Component, joint and derive errors#

• Joint errors: the origin of a joint on a face that changed. Edit the joint and reselect a stable origin.
• Derive errors: source design changed. Update, and read the timeline in the destination.
• Missing referenced files: external references that were moved or renamed; check the referenced designs in the data panel.

Failure modes and fixes#

Practice exercise#

Provoke, diagnose and repair three different kinds of failure, using numbers.

1. Build a 60 x 40 x 20 mm box, shell it 2 mm open at the top, add a 3 mm fillet to the top rim edges, and add a four-hole pattern of 5 mm holes 8 mm from the edges. Name all features and save a version.
2. Set the width to 12 mm and record every error. Which one is the first failing feature? Which failures are independent?
3. Fix the fillet by finding the largest radius that works. Test values around 0.9, 1.0 and 1.1 mm and record the boundary in your Fusion version.
4. Fix the hole pattern by replacing the edge offset with min(8 mm; width / 4).
5. Delete the profile of the extrude's sketch (by deleting a line) and read the message. Use suppress to isolate the culprit, then repair the sketch.
6. Use the binary-search procedure on a deliberately broken timeline of at least 20 features: write down how many marker moves you needed.
7. Restore nominal sizes and perform a visual check for silent reference changes (section view of the walls, measure the hole centers).

Expected result: you can name the first failure, explain why it failed, fix it within a few steps, and recognize when two failures are independent.

Related#

• The timeline
• Rollback and editing features
• Design-for-change patterns