What you're doing when you convert mesh to shape

When you import a mesh file into FreeCAD — whether it's an STL, OBJ, or another mesh format — you get a collection of triangular faces that describe a 3D surface. A mesh is just those triangles floating in space with no thickness or solid properties. A shape is a solid object that FreeCAD can measure, modify, and use for engineering work like 3D printing or CAD operations.

Converting mesh to shape means telling FreeCAD to take those triangles and turn them into a real solid object. This matters because shapes can be edited with FreeCAD's Part Design tools, combined with other objects, and exported in formats that manufacturing software understands. A mesh cannot.

The conversion process works best when your mesh is already closed and has no holes or broken edges. If your mesh is damaged, FreeCAD can still convert it, but the resulting shape may have gaps or unexpected surfaces.

Key Takeaways

  • Import your mesh file into FreeCAD using File > Open or by dragging the file into the viewport.
  • Select the mesh object in the Model tree, then use Part > Convert to Shape from the menu to create a solid object.
  • If conversion fails or produces errors, check the mesh for holes or non-manifold edges using the Mesh workbench's analysis tools.
  • After conversion, you can use Part Design tools to modify, measure, and export your new shape.
  • For meshes with significant damage, repair the mesh first in the Mesh workbench before attempting conversion.

Getting your mesh into FreeCAD

Start by opening FreeCAD and creating a new document. Go to File > Open and navigate to your mesh file. FreeCAD accepts STL, OBJ, PLY, and several other mesh formats. You can also drag the file directly into the FreeCAD window and it will import automatically.

Once imported, you will see the mesh appear in the 3D viewport and a new object will show up in the Model tree on the left side of the screen. The object name will match your filename — something like "Part" or "Mesh". This is your mesh object, and it is not yet a shape.

Check that the mesh imported correctly by rotating the view and looking for obvious gaps, holes, or missing sections. If the mesh looks broken, you may need to repair it before converting. If it looks solid and complete, you are ready to move forward.

Converting the mesh using the Part workbench

Click on the mesh object in the Model tree to select it. The object will highlight in the viewport. Now go to the menu bar and click Part. A dropdown menu will appear with several options. Look for Convert to Shape and click it.

FreeCAD will process the mesh and create a new shape object. This usually takes a few seconds. When it finishes, you will see a new object appear in the Model tree, often named "Shape" or "Converted". The original mesh object will still be there — you can delete it if you no longer need it, or hide it by clicking the eye icon next to its name.

The new shape object is now a solid that FreeCAD recognizes. You can select it, measure it, and use it with Part Design tools. If the conversion produced errors or warnings, FreeCAD will display a message in the Report View at the bottom of the screen. Read that message carefully — it will tell you what went wrong.

What to do if conversion fails or produces errors

If FreeCAD cannot convert your mesh, the most common reason is that the mesh has holes, missing triangles, or edges that are not properly connected. These are called non-manifold edges, and they prevent FreeCAD from treating the mesh as a closed solid.

To check for problems, switch to the Mesh workbench by clicking the workbench selector dropdown in the top toolbar and choosing "Mesh". Select your mesh object and go to Mesh > Analyze > Check mesh. FreeCAD will scan the mesh and report any issues it finds — holes, non-manifold edges, or faces pointing the wrong direction.

If the mesh has minor damage, you can try to repair it. With the mesh selected, go to Mesh > Clean up mesh. This tool removes duplicate faces and fixes some common problems. Then switch back to the Part workbench and try converting again. For meshes with major damage, you may need to use external repair software or re-export the mesh from the original source.

Cleaning up and using your new shape

Once you have successfully converted your mesh to a shape, you can hide or delete the original mesh object to keep your Model tree clean. Right-click the mesh object and select Delete, or click the eye icon next to its name to hide it temporarily.

Your new shape is now ready for use. You can measure it by selecting it and going to Part > Measure. You can combine it with other shapes using Boolean operations like union, difference, and intersection — these are found under Part > Boolean. You can also export it in different formats by going to File > Export As and choosing a format like STEP or IGES, which are standard for manufacturing and CAD work.

If you need to modify the shape further, keep in mind that shapes created from mesh conversion are not parametric — meaning they do not update automatically if you change something. For complex modifications, you may need to use the Part Design workbench to add features like pads, pockets, or holes manually.

When mesh repair is necessary before conversion

Some meshes are too damaged to convert directly. Signs that your mesh needs repair include: FreeCAD reports "non-manifold edges" or "open shells" when you run the check mesh tool, the converted shape has visible holes or gaps, or the shape appears inside-out or distorted.

In the Mesh workbench, try Mesh > Clean up mesh first. This removes duplicate triangles and fixes orientation issues. If that does not work, try Mesh > Fill holes, which attempts to close small gaps automatically. For larger problems, you may need to export the mesh and repair it in specialized software like Meshmixer or Blender before bringing it back into FreeCAD.

After repair, always run the check mesh tool again to confirm the mesh is now solid and closed. Only then should you attempt conversion to shape.

Frequently Asked Questions

Can I convert a mesh to a shape if it has small holes in it?

Small holes will usually prevent conversion or produce a shape with gaps. Use the Mesh workbench's Fill Holes tool to close them first. For very small holes, the Fill Holes tool often works automatically. Larger holes may need manual repair in external software.

What is the difference between a mesh and a shape in FreeCAD?

A mesh is a collection of triangular faces with no thickness or solid properties. A shape is a solid object that FreeCAD recognizes as a closed volume. Shapes can be measured, combined with other objects, and exported for manufacturing. Meshes cannot do these things.

Do I need to delete the original mesh after converting it to a shape?

No, but it is a good idea to hide it or delete it to keep your Model tree organized. The mesh and shape are separate objects, and keeping both will make your file larger and harder to navigate. You can always delete the mesh after confirming the shape conversion worked correctly.

Can I convert a mesh that is not closed or has missing parts?

FreeCAD will attempt the conversion, but the result may be unusable. Use the Mesh workbench's Check Mesh and Fill Holes tools first to repair obvious damage. If the mesh is missing large sections, you may need to re-export it from the original source or repair it in external software.

What mesh formats does FreeCAD accept?

FreeCAD imports STL, OBJ, PLY, and several other mesh formats. STL is the most common for 3D printing and CAD work. Check the File > Open dialog to see the full list of supported formats on your version of FreeCAD.