Hi. My name is Alessandro and i'm Italian. This is my first experience on shapeways and it's also my first experience with 3d software. I create an object with autocad 2008 and i tried to convert in a lot of different formats. After a little i was able to convert my work in many formats like .obj .dae .3ds and so on. but OBVIOUSLY i received this error: "Only manifold objects can be printed" Now i don't know what to do. I was able to create my project in autocad 2008 but it was my first experience with a 3d program and i don't know if i can do it again. Also i have also Blender and 3D Studio Max 2010 Trial Version but i don't know absolutely nothing about them :blush: I hope someone can help me. I don't know what to do! I attach two file: the original .dwg file and the .obj one. Thank you very much