Convert OBJ to 3MF

Why convert OBJ to 3MF?

OBJ to 3MF is a good choice when a model from Blender, a scanner or a download site needs to go into a modern slicer with more than a single grey mesh. 3MF is a zipped, well-defined format that keeps units, multiple parts and colours, so projects behave predictably in Bambu Studio, PrusaSlicer, OrcaSlicer and Cura. Geometry is converted exactly. Colours from the MTL are carried as 3MF base materials, which is useful for multi-material or multi-colour prints. Textures are not stored, since 3MF in this converter has no texture slot. Named objects in the OBJ become separate parts. Because OBJ has no unit, the numbers are treated as millimetres, and Y-up files can be rotated upright.

How to convert OBJ to 3MF

1. Drop your OBJ file (with its textures, if separate) onto the converter — it opens in your browser, nothing is uploaded.
2. Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
3. Choose 3MF as the output and click Convert. Several files download as one ZIP.

What carries over from OBJ to 3MF

What changes

• Colours from the MTL are kept as base materials; texture images are dropped.
• Separate objects or groups in the OBJ become separate parts in the 3MF.
• A unit of millimetres is written explicitly, which OBJ never stated.
• Quads and n-gons are triangulated.

Tips

• Upload the MTL alongside the OBJ if you want colours in the 3MF.
• Verify the dimension labels; if the OBJ was in metres you can change the scale.
• Open the 3MF in your slicer and check that parts are not overlapping unintentionally.
• Run the free print check on meshes from scans or game assets to fix holes.

About OBJ files

OBJ comes from Wavefront Technologies' Advanced Visualizer software in the 1980s, and it has outlived the product. A file is plain text: lines starting with v define vertices, vt texture coordinates, vn normals, and f faces that reference those lists by index. Faces may be triangles, quads or larger polygons, and the g and o keywords group faces into named objects. Appearance is not in the OBJ at all; a line called mtllib points to a separate .mtl file that lists materials with diffuse colours and texture image names. The format is verbose, has no official unit and no scene hierarchy or animation, but it is trivial to read and write. That is why scanners, photogrammetry tools, sculpting programs and game pipelines still use it to move static meshes around.

About 3MF files

3MF was designed by the 3MF Consortium, whose members include Microsoft, Autodesk, HP, Stratasys and Prusa, as a modern replacement for STL in additive manufacturing. A .3mf file is a ZIP archive following the Open Packaging Conventions. Inside it, an XML model part holds the mesh, while other parts can hold thumbnails, textures and metadata. Unlike STL, the mesh shares vertices between triangles, which makes files smaller and keeps the surface connected. The core specification defines units, build items with placement transforms, and several objects in one file. Extensions cover materials, slices and beam lattices. Bambu Studio, OrcaSlicer and PrusaSlicer save their projects as 3MF with their own settings stored in extra files, so a project from one slicer may open in another with the geometry intact but the print profile ignored.

3D printing notes

For multi-colour and multi-part prints, 3MF is the format to use. Bambu Studio and OrcaSlicer open each part as a separate object, which lets you assign a different filament or setting to each one, and Prusa-family slicers do the same. Because the unit is stored in the file, a model does not arrive at the wrong size. Be careful with project files: a 3MF saved by Bambu Studio carries printer, plate and process settings that PrusaSlicer will not apply, and some slicers pick a different default when a model has no declared plate. MeshShift writes 3MF with several parts and keeps colours as base materials, and it reads 3MF for viewing, measuring and print checks.

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