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Cura creates matter where there shouldn't be (or is my STL broken ?)


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Posted · Cura creates matter where there shouldn't be (or is my STL broken ?)

Hi everyone


It's my first post on this forum. I'm quite new to 3d printing, I've been into this for a few months and always with great success until now. I must start by saying Cura is an amazing piece of software !


Today I have the first issue with it, in a way I really don't understand. My STL is sliced in a way that would produce a very different shape, and it's a different problem depending on the orientation I choose to put the model on. The problem is very reproducible, it happens everytime with this STL. I'm having this issue on Cura version 4.4.1, on Linux Mint 20.3.


The STL has been produced by Freecad 0.20 (which I love too), the stl and .fcstd file are provided. My piece is as follows, kind of a tube with an inner thread, nothing very fancy :



I export this in STL, and then I import it into Cura, it looks fine at first. But after slicing it creates bad results. Vertically (that was my intention) it fills in part of the hole on a few centimeters :



And horizontally it misses a lot of the material :




I'm kind of lost here, my workflow was pretty fluid until then. I won't really need this piece after all, but I'd like to understand what happens here. I hope someone here may have a clue, but I'm very puzzled (and a bit worried about my future slicings !)


Thanks in advance



manchon-evac-LV-pro.FCStd.zip manchon-evac-LV-pro.stl

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    Posted (edited) · Cura creates matter where there shouldn't be (or is my STL broken ?)

    "it's a different problem depending on the orientation" 

    That is always an excellent indicator that the problem is in the model.  I uploaded it to formware.co/OnlineStlRepair and here is the report from there.


    -> Analyzed your file:
    --> 46 Naked edges (?)
    --> 0 Planar holes (?)
    --> 1 Non-planar holes (?)
    --> 100 Non-manifold edges (?)
    --> 51 Inverted faces (?)
    --> 0 Degenerate faces (?)
    --> 40 Duplicate faces (?)
    --> 0 Disjoint shells (?)
    -> Repairing: 100.00%
    ----- Repair completed in 1008ms ------
    -> Vertex count changed from 2529 to 1356 (-1173)
    -> Triangle count changed from 5120 to 2708 (-2412)


    Was the model supposed to be a tube?  The repaired model is not and the surface created mid-tube is on an angle that seems to have something to do with the helix angle of the threads.  I think this one needs to be repaired in the CAD software.

    Your uploaded model is on the right and this is in Cura's Preview "X-Ray" view.  The red areas indicate model problems.




    Edited by GregValiant
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    Posted · Cura creates matter where there shouldn't be (or is my STL broken ?)

    Thanks a lot, this is very helpful. I didn't know how to test if my stl was ok and didn't think of looking for an analyser online.

    Now I guess I have to sign up onto the FreeCad forum 😛

    Do I have to like edit the topic name to put [solved] or anything ?

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