Starter
3credits
$7.99
$2.66 each
3 downloads of any size. Good for a one-off project.
First 2 conversions free3MF → 3DMNo software installation
Convert 3MF
to 3DM online
Convert a 3MF (.3mf) print file into Rhino 3DM (.3dm) for Rhino, Grasshopper and OpenNURBS workflows. Compatible solids, shells, surfaces and curves are translated into Rhino-readable geometry without requiring desktop CAD software.
Encrypted uploads Files up to 300 MB Automatically deleted within 7 days
Upload your 3MF file
Choose one file to begin the conversion.
Drag and drop your file here
or choose a file from your computer
Browse filesMaximum file size: 300 MB
First 2 conversions free — any size up to 300 MB. Then $2.99 or 1 credit per file, charged at download.
Pricing
Pay as you go, cheaper by the pack
Your first 2 CAD file conversions are free, any size up to 300 MB, including the download. From conversion 3 on, each file costs 1 credit or a one-time payment, charged only when you click Download. 1 credit downloads any file up to 300 MB, and credits never expire.
Save 11%
Pro
5credits
$12.99
$2.60 each
5 downloads of any size. The everyday choice.
Team
10credits
$19.99
$2.00 each
10 downloads of any size. Best balance of price and volume.
Studio
15credits
$26.99
$1.80 each
15 downloads of any size. Lowest price per file.
Browser-based conversion
Use the converter without installing desktop software to move from 3MF to 3DM.
Built for rhino / opennurbs
Translate triangle meshes with declared units into the nurbs, solids, curves and meshes used by 3DM.
Ready for the next workflow
Open the result in Rhino and OpenNURBS-compatible tools for review, editing or production.
Private file handling
Converted models are not added to the public CAD library and are removed after processing.
Continue your CAD workflow
Explore Marathon
OS CAD resources
Preview a model before conversion, find an existing engineering file, open a 2D drawing, or get specialist help when a source mesh needs to be rebuilt.
Browse CAD modelsSearch ready-to-use engineering and 3D-printing files across the Marathon OS library.Browse 2D technical drawingsExplore PDF, SVG and DXF drawing resources for engineering review and documentation.Get CAD design supportWork with a vetted designer when the model needs repair, remodelling or a production-ready native file.
Simple conversion workflow
How to convert 3MF to 3DM online
Move from 3MF print file to Rhino 3DM in three clear steps.
Upload your 3MF file
Drag and drop the .3mf file into the converter or choose it from your device. Files up to 300 MB are supported.
Use 3DM as the output
This page is preconfigured for 3MF-to-3DM conversion, so you do not need to search through target formats.
Download and inspect the 3DM
Download the result and open it in your preferred compatible application to confirm its geometry and scale.
Format behaviour
What changes when 3MF is converted to 3DM?
3MF starts as polygonal surface data. Conversion packages that geometry for 3DM, but it cannot recreate the original parametric feature history automatically.
Normally retained
- Visible surface shape
- Mesh vertices and faces
- Model orientation
- Closed geometry where supported
May not be retained
- Original feature history
- Native sketches and constraints
- Exact analytic surfaces
- Unsupported texture or material data
3MF print file3MF
Rhino 3DM3DMThe resulting 3DM file is based on the source mesh. Complex reverse-engineering work may still be required for a fully editable native CAD model.
Format comparison
3MF versus 3DM
Choose the output according to what the next stage of your workflow needs.
| Feature | 3MF 3MF | 3DM 3DM |
|---|---|---|
| Main purpose | 3D printing, slicing and multi-part print jobs | Rhino modelling, NURBS surfacing and mixed geometry |
| Geometry | Triangle meshes with declared units | NURBS, solids, curves and meshes |
| Textures and UV mapping | Colours supported; textures through extensions | May contain texture references |
| Materials | Base materials and colours can be stored | Rhino materials may be included |
| Object groups | Multiple named objects in one file | Layers and object groups may be included |
| Common workflow | PrusaSlicer, Bambu Studio, OrcaSlicer and Cura | Rhino and OpenNURBS-compatible tools |
Choose 3DM when
Your next application or supplier specifically requires a 3DM file.
Rhino modelling, NURBS surfacing and mixed geometry is the next stage of the workflow.
The target geometry representation suits the downstream task.
Keep 3MF when
Your project still depends on data unique to the source format.
You need to continue editing in PrusaSlicer, Bambu Studio, OrcaSlicer and Cura.
The model is still being prepared rather than handed off.
Before continuing
Check the converted
3DM before the next step
Changing the file format does not automatically make a model production-ready. Review these checks in the application used for your next workflow.
Important: File formats may not include a standard unit definition. Always verify dimensions after conversion.
- 01
Verify dimensions and scale
Confirm that the converted 3DM file uses the expected size and unit interpretation.
- 02
Inspect the complete geometry
Check that all expected bodies, surfaces, curves or drawing entities are present.
- 03
Review surface orientation
Look for flipped faces, inconsistent normals or reversed boundaries after conversion.
- 04
Check topology and open edges
Inspect gaps, overlaps, invalid edges and disconnected geometry before downstream use.
- 05
Confirm layers and object structure
Verify that supported layers, groups and model organisation were translated as expected.
- 06
Open the file in its target application
Preview the 3DM result in the software used for the next workflow before production use.
Common problems
3MF-to-3DM conversion troubleshooting
Most conversion issues come from differences between file formats or problems already present in the source geometry.
The 3DM file has the wrong size
The source and destination tools may interpret units differently. Open the 3DM file and select the correct unit or scale.
Fix: Verify units and dimensionsTextures or materials disappeared
This can be expected when 3DM does not support the texture, UV or material information stored by 3MF.
Fix: Keep the original 3MF visual dataThe model has missing faces
The 3MF source may contain open edges, invalid polygons, overlapping geometry or inverted normals that remain visible after conversion.
Fix: Inspect and repair the source geometryThe conversion fails on a large file
High polygon counts and complex geometry need more processing. Confirm the file is below 300 MB and opens correctly in a viewer.
Fix: Simplify unnecessary geometry detailSecure processing
Your 3D files remain yours
Product models can contain confidential engineering information. Privacy and file handling stay explicit beside the tool.
Encrypted upload
Files are transferred through a secure connection.
Automatic deletion
Uploaded and converted files are deleted after 7 days.
You retain ownership
Conversion does not transfer ownership of your model.
Not publicly listed
Your uploaded files are not added to the Marathon CAD library.
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Frequently asked questions
Everything to know before converting
Quick answers about formats, pricing, file limits, conversion quality and privacy.
How do I convert 3MF to 3DM online?
Upload your 3MF file (.3mf) to Marathon OS, choose 3DM as the output format, and download the converted file in seconds — no software installation required.
Why convert 3MF to 3DM?
Converting 3MF to 3DM helps you move CAD data between tools, suppliers, and workflows without installing desktop software. Marathon OS handles the conversion in the cloud so you can download a 3DM file in seconds.
What 3MF and 3DM file extensions are supported?
This converter accepts .3mf input files and outputs .3dm. Upload up to 300 MB per file.
Is the 3MF to 3DM converter free?
Your first 2 CAD file conversions on Marathon OS are free, any size up to 300 MB. After that, each converted file needs a small fee or 1 credit, paid only when you download it.
How is my data stored and secured?
Your files are encrypted during upload, processed securely in the cloud, and automatically deleted after 7 days.
Do I need any special software or training?
No — upload your 3MF file and download 3DM directly in your browser. No plugins or desktop CAD tools required.
Can I convert large 3MF models to 3DM?
Yes — Marathon OS is optimized for large and complex CAD models. You can upload files up to 300 MB for 3MF to 3DM conversion.