Hello Jerry

As to exporting to STL both Silo and Blender will export to that format. Personally I feel that Blender would be the more robust of the two and there has been recently made tutorials of things you need to take into consideration when modeling for 3D printing here is one that maybe useful and give you some more informational insight to what you want to accomplish https://www.youtube.com/watch?v=zHxs4uerHjw 

Hope this helps some

Lobo3433

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