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.
Thanks for the positive comment.
As far as I know, Blender does not have the ability to create a STEP file. Are you simply looking for a single STL for the complete Fred Flintstone model?
I have combined all of the pieces together as a single model if that helps. Let me know and I'll post it.