Free online STP to AMF converter

A slicer or 3D-printing application may require AMF when it cannot import STEP geometry directly. Converting the file creates a printer-ready triangle mesh that can be checked for scale, watertightness, and compatibility before manufacturing.

What the STP format is

STP, also called STEP, is an ISO 10303 exchange format for 3D CAD data, usually stored with .stp or .step. It describes mathematically defined faces, surfaces, solids, assemblies, colors, and product structure rather than a fixed triangle mesh.

Mechanical CAD systems such as SolidWorks, Autodesk Inventor, Fusion, CATIA, Siemens NX, Creo, FreeCAD, and Onshape use STEP for exchanging engineering models between designers, suppliers, manufacturers, and other CAD applications. STEP files can retain accurate solid geometry, but they do not normally contain the mesh data required directly by a slicer.

What the AMF format is

AMF means Additive Manufacturing File Format. It is an XML-based standard, defined by ISO/ASTM 52915, that represents one or more objects as triangle meshes. An AMF file can declare units and include colors, materials, multiple objects, lattices, textures, and object arrangements; compressed files are commonly saved as .amf.gz.

AMF can carry more manufacturing information than basic STL, but slicer support is inconsistent. STL and especially 3MF are more commonly supported by current 3D-printing software, so confirm that the destination application can open AMF before converting.

Convert with 101convert.com

1. Open the STP-to-AMF converter on 101convert.com.
2. Upload the .stp or .step file and select AMF as the output format.
3. Start the conversion and download the resulting .amf file.
4. Open the file in the target slicer or a mesh inspection application. Check a known dimension, object placement, surface appearance, and mesh validity before printing.

Do not upload confidential engineering data unless the file-sharing and retention terms are acceptable. Large assemblies or files with sensitive supplier information are better handled in desktop software.

Convert with FreeCAD

1. Open FreeCAD and load the STEP file with File → Open.
2. Inspect the model tree and confirm that the required bodies, parts, and assembly components are visible and correctly positioned.
3. Switch to the Mesh workbench, select the required solid or solids, and create a mesh using the mesh-creation command.
4. Set linear and angular deflection. Smaller values produce more triangles and preserve curved surfaces more closely; larger values produce smaller files but increase approximation error.
5. Select the generated mesh and use File → Export. Choose AMF in the file-type selector and save it with an .amf extension.
6. Open the exported file in the destination slicer and verify its scale, orientation, object count, and mesh integrity.

The exact FreeCAD menu label and available export formats vary by version. If AMF is absent from the export file-type list, that installation cannot write AMF directly; use 101convert.com or another application that explicitly provides AMF export rather than renaming an STL file.

Quality and compatibility

The conversion changes STEP's exact boundary-representation geometry into a finite triangle mesh. Parametric features, sketches, constraints, editable CAD history, assembly relationships, and feature dimensions are not preserved.

Use finer tessellation for small holes, threads, fillets, and other curved or narrow features. Excessively fine settings can create very large files and slow slicer operations, while coarse settings can distort curves, close narrow openings, and affect printed dimensions.

Check that the mesh is watertight, has consistently oriented normals, and contains no duplicate, degenerate, or self-intersecting triangles. Confirm the intended unit system using a known measurement; AMF can declare units, but some slicers may ignore or misinterpret that declaration.

An assembly may become separate AMF objects or one combined mesh, depending on the converter. Preserve separate objects when independent placement or material assignment matters. If the target software handles AMF poorly, export 3MF instead when it is supported; 3MF generally has broader support for units, colors, materials, and build information.