Make multiple Bezier curves manifold and free of intersections, for 3D printing I'm trying to model a character to 3D print it. I'm having some trouble with bezier curves: as they are not manifold (and glitches through my mesh) my slicer can't do anything even remotely printable. The character's eye (a UV sphere) had the same effect and after some stitching it was good as new but I use around 40 bezier curves (used as hair, see below) and even after trying for 5h or so I really don't know how to stitch that !



I've already tried a lot of boolean-based solutions, didn't really work that well, mostly because the part that glitches through the mesh is copied when using a union boolean. I also tried using a union boolean and then a difference boolean using the skull of my mesh with some solidify, didn't work out that well either...



Any idea how to make this printable ? I'm on a kinda short schedule, any help is appreciated !

I think there's a better way to give you the .blend file but maybe that will do ?
I don't know what kind of mesh is needed for 3d printing, but I assume you want to remove the protruding faces from inside the face mesh. This should be possible with a script that would select the vertices of a mesh lying on one side of another mesh. Maybe someone can suggest a way to write such a script.

Here is a (rather tedious) workaround. 


In side view you do a cross section select by alt-b to select the upper part of the skull
you then box (or circle) select the vertices from inside
Turn the part round and deselect any vertices that might have got selected 
Do a delete face on all the selected vertices
Repeat this process to remove all the protruding faces of the hair mesh
Apply union modifier to create a single mesh out of the two parts


I guess (and I may be wrong), the hair part is already manifold, since the curve is converted to a surface.

Not sure if this would help you. But I am hoping to learn something myself by sharing my thoughts :)