RevarBat:

Thanks for the code. I'll have to tinker with it a while. I also found this
code on another discussion forum, I added the sphere and was trying to merge
it with the cone.

// rotate-extrude test
// by Oliver Fenn
$fn=64; // Bem .: 2nd power

// Shaping function x from [x0: xe], steadily increasing in [x0: xe]
x0=0.0;
xe=1.0;
// Examples:
// x, xx, xxx,
// 1-sin(acos(x)), 1-cos(90x), 1-cos(180x), sin(90x)
// log(x+1), 1-1/(x+1)
function f(x) = 1-sin(acos(x)); // ball, at half the height of the diameter!

// Two-dimensional polygon determined by f (x), x from [x0: xe]
module shape (start, end, to)
{
steps = (end-start)/to;
polygon
(
[
for(x=[start:steps:(end+steps)])
(x<=end)?[x-start, f(x)-f(start)]:[0, f(end)-f(start)]
]
);
} // shape

// cone over radius and height
module cone_r (rad, height)
{
hfact = height/(f(xe)-f(x0));
translate([34, 34, height])
mirror([0, 0, 1])
scale([rad/(xe-x0), rad/(xe-x0), hfact]) // Scale the cone to size
rotate_extrude()
shape(x0, xe, $fn);
} // cone_r

// construction
{
//added by FourthDr
translate([34,34,112.5])
sphere(3., $fn=100);
}
cone_r(16.945, 114.94);
// join cone_r and sphere

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The whole reason for this exercise in the first place is because I needed to
cut the part into two to fit my printer using the pizzlecut library. I think
I can eventually get this working since it's just basically a geometric
shape problem.

But with other models, this is a huge problem. I can't just easily redesign
more complex designs/shapes. Especially, since I don't always have the
original design files just an stl file. So any time there is some problem no
matter how small with the model OpenSCAD throws a hissyfit. Sometimes I can
"fix" the model where OpenSCAD will accept it. Bust most of the time not.

Case and point, I have two models attached below that I need cut into two
parts. They both look and preview fine. My slic3r has no problems. But when
I try to cut them, OpenSCAD will not render them. And in worst case such as
with the nose cone will actually crash OpenSCAD with a C++ error.

It's too bad there is not a way to just cut with defects and all. It just
needs to be accepted by a slicer and look ok to the eye. A diagnostic tool
of some sort that could fix these problem would be great. Or that could
point out problems and give suggestions on fixing them so OpenSCAD will
accept the file.

I'm trying to get these two attached stl files split by tomorrow. I've been
tinkering with them for months. So far without success. Any one interested
in seeing if they can find and correct the two files for me? And maybe give
some tips and or suggest some software tools I have not already tried?
Cryptic CGAL errors don't really help me find and fix what OpenSCAD is
complaining about.

back-cover-no-stand-2.stl
http://forum.openscad.org/file/t1425/back-cover-no-stand-2.stl
LCD_face_plate_LCD_hole_open(repaired).stl
http://forum.openscad.org/file/t1425/_LCD_face_plate_LCD_hole_open_%28repaired%29.stl
puzzlecutlib3.scad http://forum.openscad.org/file/t1425/puzzlecutlib3.scad

Thanks for all the help.

--
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That's simply not possible. I don't have the ability or programming skills to
do that. I would need to have the help of some sort of automated tool to
repair any model I might need to print. Or lots of help from some one that
is highly skilled in OpenSCAD.

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What I don't understand is how it can preview a broken stl with no problem.
But a render, which you would think uses the same process fails.

There needs to be some kind of built-in utility that can tell you just where
in the mesh it is having a problems. It's impossible to figure out a
problem, if the cause it shrouded inside of a black box. There is basically
no visualization of problem areas. Or helpful error messages.

The only way I was able to see one of the major flaws in the nose cone was
when I imported it into Tinkercad and tried to slice the cone off the base.
It was then that by chance after separating the cone from the base that I
saw a ton of artifact triangles still connected to the cone-less base. Then
I knew there where major issues with the model. But OpenSCAD said nothing
about it other than crashing when I tried to render.

So once I know there are problems. What's the easiest way to identify and
repair them without being an export. Every time I try to manually repair an
stl it breaks another part of the model in some way.

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NopHead:

You've mentioned OpenSCAD's grid a few times before. But is that actually
documented anywhere? For example, if the designer of a model was made aware
that any export to stl needed to have triangles of a specific maximum size
there would be one less problem to deal with.

That is exactly what's needed, guide lines. Any shared stl should have the
following traits. Right now you have no idea what program the stl was
originally exported from or what settings where used.

If some one could document exact minimum traits an stl file needs to be
successfully imported, manipulated, and then exported from OpenSCAD that
would be very helpful.

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