Urban tree - 3D Construction issue

Hi guys,

I have been creating this urban tree pavilion/seat and have been trying to load it to autodesk123D so I can set it out to print with a lazer cutter at 1:100 scale.

Though I have not got the results I was after.

This is the structure and in Rhino it looks fine. I have attached the rhino file and Grasshopper file. Please note I am a super newbie....

 Though when I load this into Autodesk 123D I get this happening. I have exported in stl format and obj format. the only format's it will allow from what I am told.

Not a happy file. completely loses it's solid form. and screws over the geometry.

Is it to do with the way I am exporting it or it there something wrong in my file?

Please help one struggling Kiwi.

Thanks