"Cracks" in surface

I’m pretty new to this software, so apologies if the answer to this is obvious. I sent off a file to a 3D printer, and they said my model was unprintable due to “cracks” in the surface. I see fine lines created where surfaces intersect the back of my object - I’m not sure what else they could be referring to. Could someone tell me if this would prevent printing, and if there is any way to fix this?

1-7.3dm (5.0 MB)

My surface modelling skills with this are a little limited, but yep, there’s a whole load of ‘cracks’ in that model. You might be wise to go through some of the many tutorials online and start from the beginning. Sorry couldn’t help more, hopefully someone else will chime in :+1:

For printing the model should be a “solid” which in Rhino is a closed surface or polysurface with no naked edges. A naked edge is an edge of a surface which is not joined to another edge. Use ShowEdges with the Naked edges option checked to find naked edges.

The current model is 7 polysurfaces and 14 surfaces with surfaces overlapping. There are 76 naked edges.