Blender 3MF Repair Addon

A Blender 4.5 addon that imports .3mf files, repairs non-manifold mesh geometry, and exports back as an slicer compatible .3mf — with all filament colors preserved.

Built for multi-color FDM printing on machines like the Snapmaker U1 (11-color) using OrcaSlicer.

What it does

• Imports BambuStudio .3mf files, including the component sub-file format (3D/Objects/object_1.model) used by "Image to 3D v2"
• Decodes paint_color attributes ("0C", "1C", ...) to preserve per-face filament assignments for up to 11 colors
• Repairs non-manifold mesh geometry in one click:
  • Removes duplicate vertices
  • Deletes faces causing multi-face edges (overlapping geometry)
  • Fills open boundary holes using triangle fill (no n-gon artifacts)
  • Recalculates face normals for consistent winding
  • Splits non-manifold (bowtie) vertices
• Exports as OrcaSlicer-compatible .3mf with paint_color attributes and project_settings.config filament colors

Results on a real model

BambuStudio "Image to 3D v2" cat model — 164k vertices, 329k triangles, 11 filament colors:

	Before	After
Non-manifold edges	155	0
Open boundary edges	70	0
Non-manifold vertices	133	0
OrcaSlicer errors	20	0
Colors preserved	—	11 / 11

Installation

1. Download 3mf_repair_addon.py
2. In Blender: Edit → Preferences → Add-ons → Install
3. Navigate to the downloaded file and install
4. Enable the addon (search for "3MF Repair")

Requirements

• Blender 4.5+
• Tested with BambuStudio .3mf files and OrcaSlicer on macOS

Usage

1. Import

File → Import → Import 3MF for Repair

2. Repair

With the imported mesh selected, open the N-panel sidebar → 3MF Repair tab:

• Check Mesh — reports non-manifold edges, open boundary edges, and non-manifold vertices
• Repair Mesh — runs the full repair pipeline in one click

3. Export

File → Export → Export 3MF (Repaired)

Then open the exported file in OrcaSlicer — colors and geometry should be clean.

How the repair pipeline works

1. Remove doubles — merges near-duplicate vertices within 0.001 mm
2. Multi-face deletion — finds edges shared by 3+ faces (overlapping geometry from AI mesh generation) and removes the offending faces in two passes (threshold ≥2, then ≥1)
3. Non-contiguous fix — removes faces with wrong winding relative to their neighbors
4. Hole filling — fills open boundary loops using triangle_fill (produces triangles directly, avoiding n-gon artifacts on export)
5. Winding recalc — runs recalc_face_normals on the full mesh once boundary and multi-face edges are resolved, correcting any fill faces with inverted normals
6. Bowtie vertex split — detects vertices connecting two disconnected face fans and splits them into separate vertices; cleans up resulting wire edges

How the color pipeline works

OrcaSlicer ignores <basematerials> for multi-color display. This addon uses BambuStudio's paint_color triangle attribute (e.g. paint_color="2C" for filament slot 3). Filament hex colors are written to Metadata/project_settings.config.

Filament indices survive mesh repair via a KD-tree snapshot taken before any bmesh operations (since bm.to_mesh() corrupts generic mesh attributes when face count changes in Blender 4.5). After repair, indices are restored by nearest-vertex position lookup.

Troubleshooting

"Imported 0 verts, 0 faces" — The file uses the BambuStudio component sub-file format. Make sure you're using Import 3MF for Repair (not Blender's built-in 3MF importer).

Colors missing after export — Ensure the mesh has the 3mf_filament attribute (visible in Object Data Properties → Attributes). Re-import the original file if it's missing.

OrcaSlicer still shows errors after repair — Run Check Mesh first. If it reports 0 NM edges / 0 boundary / 0 NM verts, the geometry is clean and OrcaSlicer's error is a false positive that won't affect slicing.

License

GPL-3.0-or-later

This addon imports bpy, bmesh, and mathutils — GPL-licensed components of Blender. Under the GPL, any program that links against GPL code must itself be GPL-licensed. No code was copied from other addons; the GPL applies here because of the Blender API dependency.