Preserved
- Relative part placement is preserved through baked mesh vertices before merging or splitting.
From precise CAD surfaces to polygon modeling
STEP / STP to OBJ Converter Online
Turn a STEP or STP part or assembly into Wavefront OBJ geometry for visualization and mesh editing. Choose how finely curved surfaces become triangles, inspect the model, and keep, merge or split detected parts. Exact CAD definitions and engineering metadata do not survive the mesh export.
Drop STEP or STP file here
or browse your computer
Max 100 MB · processed locally
Your model stays on this device. Parsing, conversion, verification, and download preparation run locally in this browser.
What the conversion keeps and removes
Converted
- CAD surfaces become triangle meshes at Draft, Balanced or Fine quality; curved shape is approximated.
- Detected parts can remain separate objects in one OBJ or separate files in ZIP. Assembly hierarchy and reusable part relationships are lost.
- Source units are normalized to millimeters, then converted to your selection. OBJ does not store the unit label.
- Confirm the guessed source up axis, then choose the output orientation.
- Surface orientation becomes OBJ mesh normals.
Lost
- Exact face-edge-solid relationships are lost; OBJ is not a CAD solid.
- Part and face colors are lost.
- Materials and presentation attributes are lost; no MTL file is generated.
- Exact curves, NURBS, CAD precision and any parametric definitions are lost.
- PMI, engineering tolerances, annotations and manufacturing metadata are lost.
Unsupported input
- Texture UVs are not reconstructed from CAD surface parameters.
- Textures and companion image reconstruction are unsupported.
- Cameras and lights are not converted.
- Rigs, morph targets and assembly motion cannot be reconstructed.
- Print settings and supports must be configured separately.
Can a STEP solid become an editable OBJ?
Yes, as a triangle mesh. The browser CAD engine tessellates supported STEP solid and surface faces and exports the resulting geometry with mesh normals and detected part names. This opens mechanical parts in software that expects polygons instead of B-Rep solids. STEP and STP are two extensions for the same input format, so both work on this page. Keep the source file for engineering work: changing an OBJ mesh does not edit the original CAD surfaces or dimensions.
- STEP and STP on one page
- Local CAD engine
- Draft, Balanced and Fine quality
- Detected parts as OBJ objects
- Coordinate and orientation controls
- Verified OBJ or ZIP download
What happens between CAD and OBJ
Curves are sampled into triangles
Draft favors smaller meshes; Fine follows curved faces more closely. Quality is chosen before opening the file and applies to the source tessellation and resulting OBJ. Verification compares OBJ with that tessellation, not with exact analytic surfaces.
Part placement remains visible
The CAD importer resolves the placement of detected parts. Keep writes flat named objects, Merge combines them into one object, and Split writes individual OBJ files while keeping their assembly-space positions.
Physical scale is converted explicitly
The CAD engine normalizes supported source units to millimeters. Select the intended OBJ coordinate unit and confirm the guessed source up axis. The chosen scale and rotation are applied once to the export.
How to convert STEP or STP to OBJ
Step 1
Choose quality and open your CAD model
Select Draft, Balanced or Fine, then choose a .step or .stp file up to 100 MB. Inspect the tessellated input preview and detected parts.
Step 2
Confirm units, orientation and parts
Review normalized millimeter coordinates, confirm the source up axis, select the OBJ output unit and axis, and choose keep, merge or split for multiple parts.
Step 3
Verify the mesh and download
Convert the tessellation to OBJ. Inspect the independently reparsed output preview and dimensions, then download one OBJ or a ZIP of part files. Retain the STEP original for exact CAD edits.
Move CAD parts into a mesh workflow
Prepare a mechanical part for visualization
Create an OBJ surface from a supplier STEP model for staging, lighting or material assignment in a mesh-based renderer.
Sculpt or simplify a CAD-derived mesh
Bring a tessellated part into a polygon editor for sculpting, remeshing or reducing complexity, while retaining the original STEP for precise design changes.
Hand off an assembly as named objects
Keep detected parts in one OBJ or package separate files into ZIP. Relative placement is retained, while the original assembly tree is flattened.
STEP and OBJ are different file formats
STEP exchanges CAD product data and can represent solids using precise faces, edges and curves. OBJ describes polygon geometry that a modeling application can edit as vertices and faces. Tessellation bridges those representations by sampling surfaces into triangles. It preserves an approximation of shape while removing CAD topology, precision definitions and assembly relationships.
| Property | STEP | OBJ |
|---|---|---|
| Shape representation | Exact solid and surface definitions | Tessellated triangle surface |
| Editing | CAD faces, edges and solid topology | Polygon mesh editing |
| Parts | Parts and nested assemblies | Flat named objects or separate files |
| Surface appearance | Part colors and presentation properties | Geometry and normals; no MTL or UV unwrap |
| Precision and metadata | Analytic curves, PMI and tolerances | Approximation at selected mesh quality |
| Coordinates | Declared length units; no universal up axis | Selected numeric scale and orientation |
Troubleshoot STEP to OBJ conversion
- Round surfaces look faceted
- Start over, select Fine mesh quality and reopen the STEP. More triangles approximate the same curved CAD surface more closely; OBJ cannot carry the exact curve equation.
- The file has no usable geometry
- Export solid or surface bodies from the CAD application. Wireframes, construction curves, drawings and annotations alone do not define a mesh surface.
- The OBJ size or orientation is unexpected
- Compare the displayed output dimensions with a known part dimension. Match the selected unit in the OBJ importer and confirm the source up axis, which STEP does not universally define.
STEP / STP to OBJ limitations
- STEP to OBJ replaces exact CAD surfaces with triangles. B-Rep topology, engineering tolerances, colors and assembly hierarchy are lost. Keep the STEP original for engineering edits; OBJ stores no physical unit.
- Tessellation approximates curved geometry. Download verification proves agreement with the selected tessellation, not exact equivalence to the original CAD surfaces.
- Colors, presentation materials, PMI, annotations and engineering metadata are omitted. No MTL library, texture images or UV unwrap is generated.
- Wireframe-only, drawing-only and empty files are rejected. Export self-contained solid or surface bodies with all required parts included.
- Merge combines triangle surfaces without a Boolean union. Conversion does not heal CAD geometry, close holes, weld vertices or guarantee a watertight mesh.
STEP to OBJ FAQ
Are STEP and STP both accepted?
Yes. They are alternate extensions for the same STEP CAD exchange format. Use either on this page; renaming the extension is unnecessary.
What is lost when STEP becomes OBJ?
STEP to OBJ replaces exact CAD surfaces with triangles. B-Rep topology, engineering tolerances, colors and assembly hierarchy are lost. Keep the STEP original for engineering edits; OBJ stores no physical unit.
Which mesh quality should I choose?
Balanced is a useful starting point. Fine uses more triangles around curved surfaces; Draft reduces complexity. Select quality before opening the file, then inspect the surface and triangle count.
Does OBJ retain colors, materials or CAD surface UVs?
This export contains geometry and tessellated normals without colors, MTL materials or texture images. CAD surface parameters are not converted into a texture UV unwrap.
Can I keep parts separate in a single OBJ?
Yes. Keep source structure writes each detected part as a named OBJ object. Nested assembly relationships are flattened. Split produces one file per part; Merge produces one mesh object without a Boolean union.
How do I check the scale of the result?
The CAD engine normalizes input units to millimeters, and your output selection controls the numeric coordinates. Compare verified dimensions with the known part size and use the same unit when importing OBJ.
Is my CAD design sent to a server?
No. The CAD engine and all file processing run locally in your browser, including tessellation, previews, OBJ generation, verification and packaging.
Sending the same CAD model to a slicer?
Use STEP to STL when your next application needs triangle facets for 3D printing. Choose OBJ here when named mesh objects and modeling-tool interchange matter.