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Netfabb split making surfaces that are "not closed"

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I'm trying to make 3d molds on my UM. My intended workflow was


  1. Clean 3d stl file using Netfabb Cloud
  2. Use Uniform Mesh Resampling in Meshlab to hollow the model as described here https://sites.google.com/site/3dprintfaq/workflows/hollowing-a-model
  3. "Cut" the model into two symmetric halves using Netfabb Basic
  4. Print on UM using Cura

Unfortunately, I'm stuck on point 3, because every time I try this step, Netfabb complains that the two resulting halves "are not closed". I've tried the built in repair tools and it can't fix them. I've tried exporting them as STL files and processing them in Cura in spite of the warnings, but it doesn't work, because the "hollowness" has been lost in the process.

I'm really stuck on this. If anyone has any ideas, I'd love to hear them.




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Hi Xeno,

If you can tell me how to cut it in Meshlab, that would be great. I've been through all of the menus in Meshlab and can't find a way to do it. The closest I've found is the "conditional face selection" where I can use a criterion such as (x<0) to select a subset of the faces. But this gives me a jagged edge around the x=0 axis instead of a clean line and the two halves of my mold would not be able to fit together cleanly if I go with that approach.

BTW, Owen, thanks for pointing me to the openscad "thing". I have looked at it and I'm trying to improve on it by significantly reducing the amount of material that is required. I tried scripting this in openscad but kept on finding issues with openscad being sensitive to quirks in the .stl files that I used. So at the moment I'm trying a manual workflow outside of opens cad.




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Could you post an STL?

Two things,

1. if you ran your model through Netfabb cloud then it should be hollow. Unless you have some strangley folding geometry. Shouldn't need step 2.

2. Besure when you do step 3 that when you hit "execute cut" to look under cutting options, and be sure to check "triangulate cuts".

The only time netfabb wouldn't close the mesh properly is if you are cutting something like a glass or vase though the middle where there are two complete cut edges, they would both get closed and result in non manifold geometry.

Post an STL or picture of the failed cut and I can tell you what is going wrong.


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