I found a new (at least for me) software that simulates mechanical movement.
It's called "MotionGen Pro" and runs in the browser, all you need is an account.
Export is possible as image, PDF and SVG and export from the 3D view as STL or Obj.
Excellent! And seems free! :) Export 3D from the view 3D!
Import export 2D works fine with MOi (drawing scale to regulate)
I can't exit from the 2D drawing arbitrary polygon!!! (maybe i miss something but...
Edit : I have found! You must last click near the first start segment extremity!!! :)