Good evening all,

I was hoping that someone could help me out and advise on what is wrong with my model. It's a funnel for a WW2 destroyer model. I have 3D printed it in the past, but recently downsized it a bit to make it more accurate to the plans. Upon doing so, nothing works. Netfabb and Shapeways keep trying to close the funnel off, which sort of defeats the purpose of a hollow funnel! I've tried reextruding the funnel sides, doing Boolean Unions to link up the various parts and so on. So far, nothing really works. Adding triangles in Netfabb doesn't seem to work, either; I've been trying that for two days without success.

So, would anyone be able to tell me why the model isn't manifold, and how to solve this?

Many thanks for any and all pointers.

Bob