Reconstructing STL files in FreeCAD: Reverse engineering guide

STL files are widely used in 3D printing, but are hardly suitable for subsequent editing. They do not contain parametric information, but consist of a large number of triangular surfaces. However, anyone who only has an STL file and wants to create an editable CAD model from it faces a typical challenge. The YouTube channel The Savvy Engineer shows how STL files can be reconstructed in FreeCAD and reused as fully-fledged CAD models.

The crucial step is to first convert the STL mesh into a so-called “shape.” To do this, switch from the Mesh Workbench to the Part Workbench in FreeCAD and use the “Shape from Mesh” function. This creates a geometric shape from the triangular mesh, which can then be converted into a solid. The result is an object that can be further processed like any other component in the CAD system.

In the next step, the model is converted into a solid and then exported as a refined copy. FreeCAD allows you to generate a STEP file from this – a format that is supported by almost all professional CAD programs. This means that the reconstructed object can not only be further edited, but also used for simulations or designs in other software environments.

Although this method does not replace a real parametric model, it does allow lost or incomplete design data from an STL file to be reused. This can be particularly helpful for older projects or 3D scans. In practice, it is advisable to check the generated surfaces afterwards and smooth them if necessary in order to obtain a clean geometry.