For CNC routed machining, one could use (among others) the following file types:
I recently encountered some irregularties when trying to start right from an dxf and so the need to convert an .dxf to .svg arose.
Well, it turns out when starting from Autodesk Inventor ,things are not that straigth-forward as expected.
In many cases, I am interested to cut out the face of a part. I would therefore right-click on the desired face and select export as:
I checked the .dxf file type options:
At this point, I would feel assured that the .dxf is based on the Autodesk Release 13 and safe the file in that format.
Now when I try to open/import exactly that file to Inkscape for example, it seems that the .dxf consists of polylines which finally results in the following error message:
This indicates also – in case one would want to directly use the dxf file without creating any svg or pdf – that cnc routing would not be possible due to the polylines.
Ok. Well, then let’s do as they suggest… Was just a good reason to eventually download QCAD (https://qcad.org/en/ – awesome and open source, what more could I ask for?)…
Good, so opening the Autodesk Inventor .dxf file with QCAD, save as and select: R27  DXF Drawing [Teigha] (*.dxf)
In that context: QCAD allows for directly exporting to .svg. If I want to edit the file afterwards with Inkscape it would not make any difference if I export to .dxf first and then save as .svg in inkscape or omit the .dxf step. I do prefer having a “true” .dxf file though.
I am of course not the only nor the first one, stumbling over this Autodesk Inventor DXF feature. User kjay already mentionned this back in 2013. Now four years later, I do not manage to overcome the very same issue.
To sum things up:
- [Autodesk Inventor]: export face as: .dxf
- [QCAD] open file and save as: .dxf R27 
- [Inkscape]: open file and edit.
and that being said, I usually prepare my files like this when I want to do e.g. lasercutting:
- Document properties – Resize page to content
- Stroke style: width = 0.01 mm
- Color (for cutting) : rgb(255,0,0)
- Opacity = 100%
[Memo to myself]: If ever I find some time left on my hands, I am curious to understand why Inventor dxf files contain polylines but AutoCAD’s doesn’t. Before that I will definitely need some good read on the basics of dxf files.