Repair 3D meshes online — holes, normals, duplicates

No file handy?

Duplicate vertices
Degenerate triangles
Loose shells
Holes
Face orientation
Non-manifold edges

Repair welds by position: normals are recomputed and UVs are discarded (irrelevant for 3D printing).

What this tool does

Full diagnosis: duplicate vertices, holes, loose shells, degenerate triangles and flipped normals.

One-click automatic repair, with a report of what was fixed.

Position-based vertex welding — works even on STLs with per-face normals.

Removes floating fragments with zero risk of deleting the main model.

Frequently asked questions

What defects can it fix?

The ilove3d mesh repair tool fixes the four defects that make a slicer reject an STL. Duplicate vertices: points at the same position that the file stores separately, which leaves the mesh with no real connectivity; they get welded by position. Small and medium holes: boundary edges that fail to close the surface, typical of an incomplete scan; they get filled by triangulation. Flipped normals: faces pointing inward, which confuse the slicer about what counts as the inside of the part; they get reoriented consistently. And loose fragments: islands of disconnected geometry, almost always scanning debris, discarded when they are orders of magnitude smaller than the main body. What it does not solve are very large holes, which require decisions about shape, or complex self-intersecting geometry: those need an editor like Blender or Meshmixer.

Why does my STL 'look fine' but the slicer rejects it?

Because a viewer and a slicer ask for different things. A 3D viewer only needs to draw triangles: it doesn't care whether they connect to each other or which way they face, so a broken mesh looks perfect on screen. A slicer, by contrast, has to decide for every point in space whether it sits inside or outside the part, and that can only be computed on a closed, consistently oriented surface. The defects that break that computation are invisible to the eye: reversed normals, edges with no matching pair, duplicate vertices splitting the surface into pieces that never quite touch. The usual result is a sliced file with hollow layers, infill appearing where it shouldn't, or an outright error on opening. That's why it pays to diagnose the mesh before printing rather than four hours into a failed print.

Does repairing change the model's shape?

Very little, and only where it was broken. Welding duplicate vertices moves nothing: it merges points that already occupied exactly the same position. Closing a small hole adds triangles where surface was missing, so the silhouette doesn't change. Reorienting normals doesn't touch coordinates either: it only corrects which way each face looks. The one change you will notice is that texture coordinates, the UVs, are discarded, because welding by position merges vertices that the texture was deliberately keeping apart. For printing that's irrelevant, since the material is a single colour, but if the model was also going to be used textured in a game engine or a scene, keep an unrepaired copy. The geometry itself comes out with the same millimetre dimensions it went in with: repairing is not rescaling.

What is a shell and why delete small ones?

A shell is a group of triangles connected to each other — one continuous piece of the mesh. A healthy model usually has exactly one. 3D scans, though, almost always arrive with dozens or hundreds of floating fragments: sensor noise, leftovers from the stand the object was sitting on, misread reflections. Each ends up as a tiny shell separate from the real part. To a slicer every one of those fragments is another object to print, so it generates supports and travel moves for debris the size of a grain of sand. The ilove3d repair tool removes only the shells that are orders of magnitude smaller than the main one, and the threshold can never exceed the largest shell, which makes it impossible to wipe out the whole model by accident.

Question of the month

Which printer do you use?

Repair mesh

What this tool does

How it works

Upload the broken model

Read the diagnosis

Repair and download