A missing patch, repaired step by step.
Use the built-in sample to see exactly what a repair changes. It is a deliberately damaged fixture, not a customer model.
The starting geometry
The block measures 30 × 24 × 24 mm. A 10 × 8 mm patch is missing from its top. One side triangle has reversed winding, and the bottom contains one duplicate triangle.
| Check | Original | Cleanup only | With hole filling |
|---|---|---|---|
| Triangles | 19 | 18 | 20 |
| Open edges | 4 | 4 | 0 |
| Duplicate faces | 1 | 0 | 0 |
| Winding conflicts | 3 | 0 | 0 |
| Dimensions (mm) | 30 × 24 × 24 | 30 × 24 × 24 | 30 × 24 × 24 |
Reproduce the result
- Open STL repair and choose “Try a sample”.
- Leave hole filling off and run repair. Duplicate-face and winding checks improve, but the opening stays.
- Turn on “Fill small planar holes”. Keep maximum hole span at 20 mm and run repair again.
- Compare Original and Repaired. The missing patch is closed with two triangles.
- Download the STL. Open the downloaded file again: it should show 20 triangles, no open edges and the same dimensions.
Why the span matters
The boundary bounding-box diagonal is √(10² + 8²), about 12.806 mm. A 5 mm maximum span leaves this hole alone. A 20 mm span permits it. The setting measures the diagonal in the model's original XYZ axes, not a fitted diameter.
What this proves
The fixture checks a simple planar hole, winding repair and duplicate removal. It does not establish success on damaged scans, intersecting shells or every downloaded STL. A solid-looking preview also cannot reveal a wall that is too thin for your printer.
Try the sample repair