Free online STEP to OBJ converter

Many renderers, game engines, 3D editors, and fabrication tools accept polygon meshes but not STEP solids. Converting the model produces an OBJ mesh that is easier to import and share, but it no longer contains the original CAD feature history or exact parametric geometry.

What the STEP format is

STEP is an ISO 10303 exchange format for structured product data, commonly stored with the .step or .stp extension. It can store precise boundary-representation solids and surfaces, topology, assemblies, and sometimes product or manufacturing metadata instead of a fixed polygon mesh.

Mechanical CAD systems such as SolidWorks, Autodesk Fusion, Inventor, CATIA, Siemens NX, and FreeCAD use STEP to exchange parts and assemblies between different vendors. STEP files are common when receiving engineering models, transferring manufacturing data, or retaining a vendor-neutral CAD copy.

What the OBJ format is

OBJ is a text-based polygon-mesh format supported by Blender, Maya, 3ds Max, renderers, game engines, and many visualization applications. An OBJ file can contain vertex positions, texture coordinates, normals, polygon faces, object names, and groups. A companion .mtl file can reference basic material properties and image textures.

OBJ is suitable when the destination needs a renderable or editable mesh rather than CAD features. Its simple structure and broad software support are useful for visualization and asset exchange. It does not preserve STEP feature trees, constraints, assembly intelligence, or exact analytic surfaces, and it has no universally enforced unit declaration.

How to convert a STEP file to OBJ

FreeCAD provides a no-cost desktop workflow with control over mesh density:

1. Open the .step or .stp file with File → Open. Confirm that the required parts or assembly components imported correctly.
2. Switch to the Mesh workbench and select the solid, body, or components to export in the model tree.
3. Choose Meshes → Create mesh from shape. Set the linear deviation and angular deviation. Lower values produce a finer mesh with more polygons; higher values produce a lighter mesh with more visible faceting.
4. Confirm mesh creation, select the resulting mesh, and choose File → Export. Select OBJ as the output type and save the file as model.obj.
5. If FreeCAD creates an .mtl file or texture references, keep the .mtl file beside the OBJ and preserve the referenced image paths when moving the files to another application.

For a conversion without installing software, upload the file to 101convert.com, select OBJ as the output format, and download the result. Check the resulting mesh in the destination program because an online conversion may provide fewer controls for tessellation, component separation, and materials than desktop CAD software.

Quality and compatibility limits

Tessellation tolerance determines the result. Use a smaller linear deviation for small parts, curved housings, and close-up rendering. Use a smaller angular deviation when cylinders, fillets, or other curved surfaces show visible facets. Excessively fine settings can create millions of polygons, slow imports, and consume substantial memory without improving the visible result.

OBJ does not reliably communicate whether dimensions are millimetres, inches, or another unit. Check the STEP source units and set the matching import scale in the destination application. A unit mismatch can make a model 25.4 times too large or too small when millimetres are interpreted as inches.

An assembly can export as one mesh or as multiple objects, depending on the converter and the selected components. Export components separately when the recipient needs independent parts. STEP colors and CAD materials may not map completely to OBJ and MTL, so inspect colors, normals, face orientation, transparency, and texture paths after import.

OBJ files are not automatically smaller than STEP files: a high-resolution text mesh can be large, while a STEP file may describe curved geometry compactly. Keep the original STEP file as the engineering or manufacturing master, because converting an OBJ mesh back to STEP cannot restore the original features, constraints, topology, or exact surfaces.