What we tested
| File | OrcaSlicer said | Actual problem | Result |
|---|---|---|---|
| 40 × 20 × 12 mm block, one small square missing | Error: 4 non-manifold edges. | One small hole (4 open edges) | G-code identical to the closed block |
| Two 20 mm cubes merged, wall left between them | Error: 4 non-manifold edges. | Internal wall (4 non-manifold edges in FixSTL) | G-code identical to the clean 40 mm tower |
| Two 20 mm cubes touching along one edge | No warning | 1 non-manifold edge; FixSTL leaves it unchanged | Sliced as two cubes joined along a line |
| 40 × 20 mm surface, no thickness | Error: 16 non-manifold edges. | Open sheet, height 0 | Nothing to slice: the plate was reported empty |
| Thingi10K 48352 by rweaving (CC BY-SA) | Error: 210 non-manifold edges. | 2 holes; FixSTL filled them into a verified solid | Filament 3615.31 mm before, 3615.33 mm after repair |
What is going on
The tooltip text says non-manifold, but the code fills the number from open_edges (source), and OrcaSlicer counts a mesh as manifold when it has no open edges (source). Two cubes touching along one edge, which are truly non-manifold, showed no error in our test.
Since 2.4.0, Fix Model also works on macOS and Linux (release notes). 61 of the 200 public test files showed this error; FixSTL repaired 13 of them to a verified solid.
What was actually wrong
How to fix it
- Check the file in FixSTL to see whether the edges are holes, an internal wall or a sheet.
- Repair holes in FixSTL or with OrcaSlicer's Fix Model; give a sheet thickness in your modelling program.
- Re-import and confirm the warning icon is gone.
- Scrub the layer preview through the area that was open.
Source: Vendor source code · github.com · OrcaSlicer 2.4.2 on macOS