Create FreeCAD parts from SVG plans
Sometimes you want to build a 3D CAD model from a set of planar drawings (for example 2D cutfiles meant for laser cutting).
Convert image to SVG
If your drawing is already in a vector format like PDF or DXF then all you have to do is open the file in Inkscape. If the file is in a raster format like JPEG or PNG you can first load it in an image processing app like GIMP and convert it to black and white, stretch the contrast and threshold the image. Afterwards you can use AutoTrace to convert it to a vector format. Autotrace can be used directly or invoked from inside Inkscape.
Here is an example cutfile take from the Flone project:
Prepare SVG
After opening your file in Inkscape, you need to single out the part that you want to work on by copying it to a new document. In this document you need to set the outline of the part to be a 1 pixel-thin line and make sure the scale of the part is correct. Export the part file as SVG.
TODO: part image
Import SVG into FreeCAD
In FreeCAD, open the Draft workbench and from the File menu select the Import option, then choose your SVG file and select the option to import the file as geometry. Check the contour for any missing bits and fix the file in Inkscape if necessary.
For each closed contour, select all objects that make up the contour and use the Upgrade tool to convert them to a Wire and then to a Face object. Next, go to the Part workbench and extrude each face to the desired thickness.