[MakerBot] missing holes

[Chris Frayda]

Hi all,
I am having difficulty printing my own design. It is about 2 cm wide
with an 8 mm vertical hole in the center, and wings sticking out on
either side. So far, I have not been able to create the hole on the
Makerbot.

*I drew it up as a X & Y mirrored mesh in Blender 2.49b, and exported it
as an STL file (STL... option, not ASCII STL option. Previous
experiments with the ASCII don't have the object mirrored.).
*If I try to use it as a source in OpenSCAD 2010.02, it crashes with a
runtime error.
*Skeinforge 2008/21/11 generates something that is missing the hole. I
can see it in the preview. It has other flakiness, but the absence of a
hole is the most annoying.

My theory is that my STL file is bad (triangle orientation/intersecting
triangle?). Do you have any ideas about how to make a better one?
Convert from *.blend file? Repair the current one? Other ideas?
Previous group email help I've missed?

Thanks in advance for any help! My apologies for not having a sample
file to attach yet. I have time to email today, soon I hope to have
time to reproduce it in a smaller design,
Chris
P.S. Makerbot 871 is printing!

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[Christine]

The blender and stl files are located on Thingiverse.
http://www.thingiverse.com/thing:2582

Looking forward to your comments!
Chris

[ddurant]

I'm not a blender expert by any means but is the object supposed to be
hollow? If I move the view around while in blender, it definitely
looks hollow. Setting Occlude Background Geometry makes this easier to
see.

I also see something funky on the top 4 faces right around the center.
They're rendering funny, like the flickering you get when there are
two faces at the exact same spot. Don't know what's up with that.

If I were to try making something like this, I'd probably start with a
1/4 cylinder, cut out the center hole, extrude up, mirror. Just a
plain, boring bead. If you can get that to skeinforge correclty and
print, it makes a good start for adding cool details to the top. Then
again, I'm not really a blender person..



On Apr 27, 9:38 pm, Christine <cfra...@rochester.rr.com> wrote:
> The blender and stl files are located on Thingiverse.http://www.thingiverse.com/thing:2582

[Jordan Miller]

Hi Chris,

your object is non-manifold. see here:
http://wiki.makerbot.com/how-to-print#toc8

you need to make the hole in the top connect to the hole in the bottom. also, each 1/4 of your bead is not connected to its neighbors. There are missing faces.

cheers,
jordan

[Nick Ames]

To start with, you don't have any faces around the hole, so your object
is just a shell. The edges of the mirrored part were intersecting the
axises, so they weren't actually connected. Also, the two vertices mid
way up the hole were part of the edge of the hole, preventing the object
from being manifold. Finally, the bottom of the hole had bizarre faces
without edges (something I've never seen before), and in line with other
edges (which caused the flickering).

I've attached a fixed up version. The fixed object is in layer 1. Its
mirror modifier has been applied, and there is a copy of the object with
its mirror modifier not applied (but missing most of the fixes) on layer 2.

PS: I think you will need to make the object larger than 10mm in
diameter if you want it to print with any detail on the makerbot.

[Christine]

Thanks to all!

I hopes of printing something with a hole!

[ddurant]

I don't know what your blender experience is but I just stumbled
across an old thingiverse blog that reminded me of this thread..

http://blog.thingiverse.com/2009/05/05/blender-quicktip-the-f-key/

[Paul Huckabee]

Christine,

I just put together a quick screen cast of how to do difference modeling in blender. Sorry there is no audio but I am at work. If this is helpful let me know and I will try to do some better tutorials.

hope this helps

Blender Difference HowTo

[Paul Huckabee]

Here is another screencast with the keyboard monitor in a much more pleasing location :)