What is a non-manifold edge?

An edge used by three or more triangles. A watertight printable surface normally has exactly two triangles on every shared edge.

What is a bow-tie vertex?

A vertex where two otherwise separate surface fans meet at a single point. Every edge can still look manifold, but the vertex is not a single disk-like neighborhood.

Does this guarantee a watertight model?

No. The tool removes conflicting faces and fills simple loops, but it does not find self-intersections or reconstruct complex damaged regions. Check the reported boundary edges and run a slicer.

Why did the tool remove a face I wanted?

Face selection is based on edge winding and area, not on the model's intent. Internal fins or overlapping shells can look ambiguous; keep a backup and inspect the result.

Will repair preserve the model's dimensions?

Vertex positions are not rescaled; welding and face removal can delete small features, but the remaining geometry keeps its coordinates. Compare before and after bounds and triangle counts.

Mesh repair/Topology

Repair non-manifold mesh (local)

Repair edge and vertex non-manifold junctions locally. The Worker parses STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF, removes excess faces on non-manifold edges, closes the simple holes it opens, and splits bow-tie vertices into separate fans without uploading the mesh.

ReadyNo uploadWorkerSTL · OBJ · PLY · 3MF · GLB · glTF

Tool facts

Formats: STL · OBJ · PLY · 3MF · GLB · glTF
Output: Mesh file
Worker: Yes
Max file: 500 MB
Runs: in your browser

Why local

Repaired mesh

No upload

Repaired mesh

Weld tolerance is 0.001 source units. The largest opposite-winding pair survives each non-manifold edge, and simple loops opened by face removal are filled. Bow-tie vertices are split into separate fans. This is not a self-intersection or CSG repair; inspect the result before printing.

Drop a non-manifold mesh

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Excess faces at non-manifold edges are removed, simple holes closed, and bow-tie vertices split; output is binary STL.

STL · OBJ · PLY · 3MF · GLB · glTF → STL

Drop a non-manifold mesh

STL, OBJ, PLY, 3MF, GLB, or a self-contained glTF. Excess faces at non-manifold edges are removed, simple holes closed, and bow-tie vertices split; output is binary STL.

Choose a file

Max file size: 500 MB · No upload

No upload · File.slice() / ArrayBuffer → Worker → repaired STL.

How it works

1
Drop a mesh file in any supported format.
2
The Worker welds vertices at 0.001 source units, removes degenerate and duplicate triangles, and checks edge incidence.
3
On each non-manifold edge, the largest pair of opposite-winding faces is kept and excess faces are removed.
4
Simple boundary loops opened by face removal are filled; bow-tie vertices are split into separate surface fans.
5
Download the repaired binary STL and verify it with the manifold check or a slicer.

What the numbers mean

Non-manifold edges

An edge shared by three or more triangles is non-manifold. The repair keeps one forward and one reverse triangle, preferring the largest faces, so the output edge has at most two incident triangles.

Vertex fans

A bow-tie vertex joins two surface fans without a shared edge. Edge counts alone cannot see it; the repair finds connected corner fans and duplicates the vertex for each fan.

Limits

This is a topology heuristic, not a CSG or self-intersection repair. Removing conflicting faces can delete intended geometry, and complex non-planar boundaries may be skipped; inspect the result before printing.

Printing notes

Run manifold-check after repair and confirm that non-manifold edges and vertices are zero.
Look for thin slivers or missing walls where the repair removed faces, especially around internal fins and touching bodies.
If a repair removes too much geometry, separate the model into parts in CAD and repair each shell instead.
Slice the repaired STL in Cura or PrusaSlicer before printing; a manifold mesh can still contain self-intersections.

Questions

References

· ISO/ASTM 52900
· Mesh topology: non-manifold edges and vertex fans