[[File:sketchup logo.png|150px]] 3D modeling ([https://www.sketchup.com/download download]) pro is free for 30 days, then you keep the basic version.
[[Sketchup Reference]] '''To use Sketchup make, you need to export sketchu pfiles sketchup files as dxf or stl using a plugin'''. This one works: http://www.guitar-list.com/download-software/convert-sketchup-skp-files-dxf-or-stl