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Forum: 3D Design
 Topic: mesh quality requirements
mesh quality requirements [message #98661] Tue, 16 September 2014 07:54 UTC
avatar FabriceN  is currently offline FabriceN
Messages: 1
Registered: October 2013
Go to all my models
Junior Member
Hi !
Last November, I modeled a phoenix (see fig1), intented to be a colar for my daugther's birthday. It is fairely small: 4.5 cm (wing to wing) x 7 cm.
The purpose was to print it in raw brass ("raw" to avoid destruction when sanding). But it was refused due to bad mesh quality, while it did printed correctly in plastic.
Mesh quality problems are real: fig2 shows that the small caps ending each "wire" were generated incorrectly (some intersecting and bad oriented faces).
Beside, there are also a few thin walls (see fig3) but these weren't the reason mentionned (and it did print well in plastic, again).

I'm puzzled because I wonder if these real but small and isolated mesh quality problems were really an issue or just a too conservative (but blocking) test run in the case of metal print (since printed correctly in plastic).
My problem is that
- the mesh seems impossible to clean-up,
- re-modeling it is painful to me (and could fail again, so I'ld like to know what is important and what is not in terms of mesh quality),
- it that it might be that simple editing makes it reasonnably printable.

ideas, suggestions ?

BTW:
- I heard that I could decide to "print as it is (with risks)", but didn't found where to click.
- On the preview and on the printed plastic version a part of the mesh has disappeared: a plate (figured in pink in fig3) added in the back so as to channel the colar wire. It was a flat brick intersecting the bird mesh. Why did it disappeared ? should I have merged or group the to meshes ?

thanks,

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Re: mesh quality requirements [message #98667 is a reply to message #98661 ] Tue, 16 September 2014 09:20 UTC
avatar mkroeker  is currently offline mkroeker
Messages: 1827
Registered: June 2012
Go to all my models
Shapie Expert
It might help to know the actual rejection message from shapeways service for your metal print. Mesh quality as such is probably not an issue if the exact same model printed in plastic - the shapeways "mesh medic" tool should automatically repair misoriented patches and similar small flaws on upload. Did you try checking/repairing your model in netfabb studio basic (multiplatform freeware from netfabb.com) ?
Or does "refusal" just mean the wall thickness tool complaining about the highlighted areas in the screenshot you posted ? You might want to measure these in your modeling software (or in netfabb) and compare to the minimum wall and wire thicknesses as listed on the materials page for brass. Some of the warnings from the wall thickness tool may actually be spurious (rounding errors, wall rules applied to surface details) and all should be informational only - you should still be able to order the print, at which point its printability will be checked by humans.

With regard to your other questions, the "print it anyway" option (a small checkbox next to your model in the "shopping cart") is not available for all materials. The plate disappearing would suggest either that it was not intersecting the bird mesh and too small to stand on its own, so automatically removed - or the intersecting area was so fraught with mesh errors that autorepair chose to remove the entire plate. (Vague third possibility: the plate had no thickness). In either case, if you do not see it in the previews it would be surprising if it showed up in the actual print.

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