I am trying to 3D print a bridge which is over 1 metre long in two parts. On the part 1 when i put it through netfabb it seems all fine but it won't upload to shapeways. On the second part there seems to be a problem with non-oreintable surfaces and won't upload either. All the parts are non-manifold and I am having trouble fixing the model to upload. Not sure if it is a problem with the intersecting shells. Any advice would be much appreciated.