Hello! I've never done 3D before, and I've tried using Google Sketchup 8 (free). The model is not completed yet, but I just wanted to know how much it will cost to print (more or less). So... I've exported the model to STL via the plugin (simply File -> Export to DXF or STL -> Millimiters -> stl) and sent to the website, but an email informs me there are some errors. How can I debug the model? Attached is the 3D model (in skp, Google Sketchup format). I'd attach the STL too, if you require it. Thanks! P.S. I've exported only the main building, not the bricks. P.P.S. I know I'll hollow the bricks once I've understood how to debug all the things. EDIT: using netfabb's repair tool, I get these results after the process: Edges: 95268 Triangles: 63512 Shells: 91 Border edges: 0 Invalid orientation: 13482 Holes: 0 In the tutorial it is written that Shells should be 1 for one object (mine is one made out of the "bricks"). Even though it's not necessary to be one, I think it shouldn't be 91 O.Ã²... and there are still 13482 invalid edges (about 30%, maybe more of the model is colored in red). Should I adopt a totally new way of designing the 3D model? I just created the walls and rotated one to make the other 3.