Tukukkk

I found some [STL files for a 3D printer[(https://www.thingiverse.com/thing:2162969), which are mainly linear extrusions of a 2D shape:

I would rather cut on a laser cutter. How can I convert them to a 2D SVG file?

One solution is a script in OpenScad, inspired from batch processing in OpenScad, which projects the 3D shape along the Z axis, and then export it as SVG:

param1=0; // param1 is the keyword of the first shell argument

FileToLoad=param1;

echo(FileToLoad);

projection() import(FileToLoad);

and then a bash script to process all STL files in the Downloads folder, including subdirectories, assuming that the above code is in ~/Downloads/slicer.scad:

for entry in $(find ~/Downloads -type f -name *.stl)



do

    new_entry=$(echo $entry | sed 's/.stl/.svg/g')



    openscad -o $new_entry -D param1="$entry" ~/Downloads/slicer.scad

    echo "$new_entry"

done

If one opens the STL file in a cad program and watches the model in XY plane, he can see something which is at first quite promising:

I thought at first that saving the projection as PDF, opening it in Illustrator or Inkscape and deleting unwanted lines does the trick.

BUT...

The STL is actually a 3D surface made of thousands of small triangles. Here's a piece seen from tilted direction:

There's no curves. The XY plane projection contains thousands partially overlapping straight line segments. They freezed Inkscape and made Illustrator slow. Any attempt to make a single shape with the Shape builder freezed Illustrator.

The downloaded shapes are quite simple so I recommend you to redraw them. If you get the XY plane projection to Illustrator as I did, you can lock it and draw with the pen tool your own version. As well you can use a screenshot as your model. You can get the screenshot for example from SketchUP.

Screenshot is so light computer load that you can draw on it also in Inkscape.

Drawing it is also the way to get non-overlapping contiguous paths. I bet the laser cutter wants them.

Any decent CAD app will open an STL, and you should be able to set up an orthographic projection and export or save out as SVG.

Heck, you could do this with Blender, or OnShape... or even Draftsight or FreeCAD I think - and all of these are freeware.