Free under 5 MB3DM → STEPNo software installation

Convert 3DM to STEP online

Convert a Rhino 3DM (.3dm) model to STEP (.step or .stp) for mechanical CAD, supplier handoff and CAD/CAM workflows. Compatible NURBS and B-rep geometry can transfer, while Rhino-specific layers, blocks, annotations, materials and mixed mesh data may change or be omitted.

Encrypted uploads Files up to 300 MB Automatically deleted within 7 days

Upload your 3DM file

Choose one 3DM file. This page is already configured to create STEP output.

Secure

Drag and drop your 3DM file here

or choose a file from your computer

Browse files

Maximum file size: 300 MB

Files under 5 MB convert and download free. Larger files use one credit for one completed download, regardless of file size.

Pricing

Pay as you go, cheaper by the pack

Files under 5 MB convert and download free. Larger files use one credit for one completed download, regardless of file size. 1 credit downloads any file, any size, and credits never expire.

Starter

3credits

$7.99

$2.66 each

Save 11%

3 downloads of any size. Good for a one-off project.

Pro

5credits

$12.99

$2.60 each

Save 13%

5 downloads of any size. The everyday choice.

★ Most popular

Team

10credits

$19.99

$2.00 each

Save 33%

10 downloads of any size. Best balance of price and volume.

Studio

15credits

$26.99

$1.80 each

Save 40% · best value

15 downloads of any size. Lowest price per file.

Just need one? Pay $2.99 for a single downloadNo subscriptionCredits never expireInvoice on every purchase

No desktop software

Start the 3DM-to-STEP workflow in your browser without installing a CAD application or plugin.

Built for Rhino-to-CAD exchange

Preserve compatible solids and surfaces for STEP-based workflows while keeping the original 3DM as the source of truth.

Ready to inspect

Open the STEP result in SolidWorks, Fusion 360, Inventor or the receiving CAD/CAM system and check bodies, units, trims and assembly expectations.

Open STEP viewer

Private file handling

Files stay private, are never added to the public CAD library and are automatically deleted within 7 days.

Continue your CAD workflow

Inspect the 3DM, verify the STEP or request specialist help

Inspect the source 3DM, validate the STEP output and use design support when Rhino-specific content must be rebuilt for the receiving CAD system.

Check the source 3DMReview solids, surfaces, curves, meshes, layers and visible objects before conversion.Open 3DM viewerInspect the STEP outputConfirm that expected solids and surfaces open at the correct size and that trimmed faces and body status are valid.Open STEP viewerNeed a clean mechanical CAD model?Ask a CAD designer to rebuild missing features, assemblies, drawings, tolerances or Rhino-specific construction data in the target system.Hire a CAD designer

Simple conversion workflow

How to convert 3DM to STEP online

Move from a Rhino 3DM model to a STEP exchange file in three steps.

01

Upload the 3DM file

Choose a .3dm file up to 300 MB. Remove hidden or duplicate geometry and confirm document units before conversion.

02

Convert to STEP

The route is preconfigured for STEP. Start the conversion without searching through a destination-format menu.

03

Download and verify

Open the .step or .stp file in the receiving CAD system. Check units, body count, trims, open edges and whether meshes transferred acceptably.

Convert 3DM to STEP

Format behaviour

What actually happens when 3DM is converted to STEP?

3DM can store NURBS curves and surfaces, B-reps, meshes, layers, blocks, annotations, render materials and application-specific data. STEP focuses on product geometry and structure. Compatible NURBS/B-rep solids and surfaces generally translate best; meshes may remain faceted, while Rhino-specific organization and presentation data may not have an equivalent.

What is normally retained

  • Compatible NURBS and B-rep shape
  • Solid and surface geometry where supported
  • Model orientation and explicit units
  • Separate bodies or parts where supported
  • Basic names or product data when mapped

What is not retained or may change

  • Rhino history and application-specific objects
  • Some layers, blocks and object attributes
  • Annotations, layouts, lights and render settings
  • Materials, textures and UV data
  • Mesh editability and some curve-only construction geometry
Rhino 3DM3DM
STEP modelSTEP

Format comparison

3DM versus STEP

Choose the format according to what the next application needs—not because one is universally better.

Feature3DM 3DMSTEP STEP
Data modelNURBS, B-reps, meshes, curves and scene dataProduct geometry, B-rep solids/surfaces and structure
OrganizationLayers, groups, blocks and object attributesParts/assemblies and product names where mapped
Visual dataCan store materials, textures, lights and viewsLimited presentation support in typical exchange
EditabilityRich Rhino-native modeling dataImported geometry without Rhino history
Best useRhino design, surfacing and mixed geometryMechanical CAD/CAM and supplier exchange

Choose STEP when

A mechanical CAD or CAM system requires STEP

A supplier needs neutral B-rep geometry

Compatible solids and surfaces matter more than Rhino scene data

You will keep the 3DM as the editable source

Keep 3DM when

You are still editing in Rhino

Layers, blocks, materials or annotations matter

The file contains important meshes or plugins

No STEP-based downstream requirement exists

Before continuing

Check the converted STEP before using it

STEP is a strong geometry exchange format, but it is not a complete copy of the Rhino document. Compare geometry and organization before release.

  1. 01

    Verify units and scale

    Compare Rhino document units with the imported STEP units and measure a known feature.

  2. 02

    Count solids, surfaces and meshes

    Confirm that every expected visible body transferred and note any mesh-derived output.

  3. 03

    Inspect trimmed surfaces

    Look for gaps, missing trims, sliver faces and naked edges.

  4. 04

    Confirm body status

    Check whether objects arrived as solids, open shells or separate surfaces.

  5. 05

    Review names and organization

    Verify part names, layers, groups and blocks where they matter downstream.

  6. 06

    Open the exact receiving system

    Test the STEP in the CAD/CAM application and version used by the recipient.

Common problems

3DM-to-STEP troubleshooting

Most issues come from mixed geometry, damaged trims, plugin-specific objects, hidden data or differences between Rhino organization and STEP product structure.

Surfaces arrive with gaps

Cause: Trims or tolerances do not sew cleanly in the target kernel.

Fix: Join/heal geometry in Rhino, reduce naked edges and export again.

Meshes are missing or faceted

Cause: Mesh objects have no native B-rep equivalent.

Fix: Convert or rebuild critical mesh geometry before STEP export.

Layers or blocks changed

Cause: STEP product structure does not map one-to-one with Rhino layers and blocks.

Fix: Use clear object/part names and verify organization after import.

Materials or textures disappeared

Cause: Typical STEP exchange does not preserve Rhino rendering data.

Fix: Keep the 3DM and texture assets for visualization workflows.

The model is the wrong size

Cause: Document and import units were interpreted differently.

Fix: Set explicit Rhino units and verify a known dimension in the STEP.

The recipient needs editable features

Cause: STEP transfers geometry, not Rhino modeling history or a target-native feature tree.

Fix: Rebuild the required features in the destination CAD system.

Hire a CAD designer

Secure processing

Your design files remain yours

Engineering files can contain confidential geometry and documentation. Marathon OS keeps conversion uploads separate from its public CAD library and explains how each file is handled.

Encrypted transfer

Files are transferred over an encrypted connection.

Automatic deletion

Uploaded source files and converted outputs are automatically deleted within 7 days.

You retain ownership

Uploading or converting a file does not transfer ownership of the design to Marathon OS.

Never published automatically

Conversion files are not listed in the public Marathon OS CAD library.

Use tools that support the same 3DM-to-STEP workflow.

3DM

3DM file viewer

inspect the Rhino source

STEP

STEP file viewer

verify the converted result

STEP3DM

STEP to 3DM

move STEP geometry into Rhino

3DMIGES

3DM to IGES

create a legacy surface-exchange file

STEPSTL

STEP to STL

create a mesh for 3D printing

CAD

Hire a CAD designer

rebuild production-ready geometry

Explore adjacent engineering and mesh handoffs.

STEPSTL

STEP to STL

CAD to printable mesh

STLSTEP

STL to STEP

mesh to CAD exchange

OBJSTEP

OBJ to STEP

mesh to CAD exchange

STEPIGES

STEP to IGES

legacy surface exchange

IGESSTEP

IGES to STEP

legacy surfaces to STEP

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Find an existing model before rebuilding one

Search the Marathon OS library for a usable starting model. Review dimensions, licensing and manufacturing suitability before using it.

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Frequently asked questions

Frequently asked questions about 3DM to STEP conversion

Clear answers about output behavior, compatibility, pricing, file limits and privacy.

  • How do I convert 3DM to STEP online?

    Upload 3DM (.3dm), confirm STEP as the preselected output, convert and download STEP (.step, .stp). Verify the result in the target application.

  • Why convert 3DM to STEP?

    Convert 3DM to STEP when a mechanical CAD/CAM system, supplier or manufacturer needs neutral product geometry rather than a Rhino document.

  • What 3DM data may not survive STEP conversion?

    Rhino-specific history, layers, blocks, annotations, render materials, textures, views and plugin objects may change or be omitted. Compatible B-rep solids and NURBS surfaces transfer most reliably.

  • Which 3DM and STEP extensions are supported?

    This route accepts .3dm input and creates .step, .stp output.

  • Is the 3DM to STEP converter free?

    Files under 5 MB can be converted and downloaded free. Larger files use one credit for one completed download.

  • What is the maximum 3DM file size?

    You can upload a 3DM file up to 300 MB. Files with many detailed surfaces, meshes, blocks or hidden objects may take longer and create complex STEP output.

  • How are my files handled?

    Files are transferred securely, are not published to the public CAD library and are automatically deleted within 7 days. You retain ownership.

Need a target-native production model?

STEP is excellent for exchange, but it does not recreate a SolidWorks, Inventor or Fusion feature tree. Use a CAD designer when the recipient needs editable features, drawings, tolerances or assembly structure.

Hire a CAD designerConvert another 3DM file