Free online FCSTD to STEP converter

What the FCSTD format is

.FCStd is FreeCAD's native document format, used by FreeCAD users for parametric 3D models and related project data. A file can contain sketches, constraints, Part Design bodies, Part workbench solids, assemblies, spreadsheets, expressions, feature history, and other document objects.

FCSTD preserves FreeCAD-specific design intent and dependencies. It is not a neutral interchange format, so other CAD programs generally cannot reproduce its sketches, feature tree, constraints, expressions, or workbench-specific history directly.

What the STEP format is

STEP is the neutral ISO 10303 CAD exchange format, commonly saved with the .step or .stp extension. It is supported by FreeCAD and major CAD, CAM, manufacturing, inspection, and 3D-viewing applications.

STEP normally represents parts and assemblies as precise boundary-representation geometry, including faces, edges, holes, and surfaces, rather than as a triangle mesh. This makes it more suitable than STL when the recipient needs CAD editing, dimensional inspection, machining, or manufacturing. STEP does not normally preserve the original FreeCAD feature history or parametric design relationships.

How to convert FCSTD to STEP in FreeCAD

1. Open the .FCStd file in FreeCAD.
2. Recompute the document and check the Model tree for feature errors. Use the document's recompute command or run doc.recompute() in the Python console.
3. Select the body, part, solid, or assembly objects to export. Exclude construction geometry, sketches, hidden alternatives, and reference objects that the recipient does not need.
4. Choose File → Export.
5. Select a STEP file type, specify a filename ending in .step or .stp, and save the file.
6. Open the result in FreeCAD or the receiving CAD program. Check the number of solids, assembly positions, units, and several critical dimensions.

The exact export label can vary by FreeCAD version, but STEP export is provided by the standard FreeCAD installation. For a repeatable local conversion, use the Python console or a macro:

import FreeCAD
import Part

doc = FreeCAD.openDocument("/path/to/input.FCStd")
doc.recompute()
Part.export([doc.getObject("Body")], "/path/to/output.step")
FreeCAD.closeDocument(doc.Name)

Replace the paths and object name with values from the document. To export several specific shape-bearing objects, pass them in one list. Exporting doc.Objects indiscriminately can include sketches, construction objects, spreadsheets, and other items that are not intended as STEP geometry.

Users can also convert the file on 101convert.com for free without installing software. A local FreeCAD conversion is preferable for confidential or commercially sensitive models because an online conversion requires uploading the source file.

Quality and compatibility considerations

STEP transfers the exported geometric result, not the editable FreeCAD construction process. After conversion, changes to the STEP model normally require direct CAD editing or rebuilding the model in the recipient's application.

Confirm that the final feature has a valid shape before export. A failed feature, an empty body, or an incorrect selection can create a STEP file with missing geometry or no usable solids. If the document contains multiple bodies, decide whether they must remain separate parts or be exported as an assembly.

STEP can carry colors, object names, assembly relationships, and metadata, but support varies by exporter, STEP application protocol, and receiving program. If the recipient specifies a protocol, configure it under FreeCAD's STEP import/export preferences when that option is available; AP214 and AP242 are common choices, but the supported options depend on the FreeCAD version.

STEP includes unit information, but import settings can still produce an apparent scale error. Measure a known feature or the model's bounding box after import. Also inspect curved faces, small features, threads, fillets, and gaps: tolerance differences between CAD kernels can alter or reject geometrically difficult features even when the main solid appears correct.