I was investigating ways of filleting cylinders to make "cup" shapes and
thought I would be clever by hulling a torus with a regular cylinder, but I
consistently get a "non manifold" error when slicing the output.

Here is my code:

fillet_radius = 5;
inner_r = 30;
outer_r = inner_r+5;
cup_height = 70;

difference()
{
// outer cup
cylinder(h=cup_height, r=outer_r);

// inner cavity
translate([0, 0, fillet_radius])
	Cup(cup_height, inner_r, fillet_radius);

}

module Cup(height, radius, fillet_radius)
{
translate([0, 0, fillet_radius])
hull()
{
Ring_torus(R = radius-fillet_radius, r = fillet_radius);
cylinder(h = height-fillet_radius, r = radius);
}
}

module Ring_torus(R, r)
{
rotate_extrude()
translate([R, 0, 0])
circle(r);
}

I have tried unioning the various parts before hulling, and also replacing
the hull with unions of cylinders (one large one, one small one, and a ring
torus to bridge the two) but the error persists.

I've tried adding fudge factors in case there's a problem at the toroidal
'equator' but it doesn't help.

Interestingly, the problem doesn't occur if I don't union or hull the torus
with a cylinder. Is there a winding issue with objects created with
rotate_extrude() that only manifests when unioned with another object?

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View this message in context: http://forum.openscad.org/Non-manifold-when-union-or-hull-a-torus-created-with-rotate-extrude-tp10448p10472.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

I read that one on nabble, it must have been deleted.

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View this message in context: http://forum.openscad.org/Non-manifold-when-union-or-hull-a-torus-created-with-rotate-extrude-tp10448p10473.html
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