MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
I just posted a make for my failed first attempt to print this. I recommend reading it before trying. You might be able to avoid my mistakes.
FYI: The inner/outer diameter of the spring slot are ~ 10mm/12mm