Gaps in Walls

Discussion in 'Calibration, Help, and Troubleshooting' started by Jasons_BigBox, Nov 23, 2016.

  1. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Morning all,

    I keep having issues on thin walls where the inner and outer faces are not joined together and leave a small gap. Picture below illustrates:

    DSCF0001 - Copy.JPG

    You can see that the thin wall has a gap, you can push a fingernail into it. The thicker section has over extruded infill on it. I'd like to stop that too if possible but no.1 is to get the walls joined together.

    I'm using Simplify 3D and you can see that it shows the gap too!

    Untitled.jpg


    Any ideas how to fix it? Under 'Advanced' in the process menu I've got "Allow gap fill when necessary" set to 50%



    Thanks everyone!
     
  2. Alex9779

    Alex9779 Moderator
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    Easiest would be if you could post a factory file. That way I just can play with it myself...
     
  3. Falc.be

    Falc.be Well-Known Member

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    unfortunatly S3D is pretty quirky with thin walls, hqving the same problem atm
     
  4. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Hi Alex,

    Thanks, file attached. One thing I noticed is that I had the outlines set to 6 (from a previous print) but changing that doesn't change the wall. I can get an infill if I only have one outline.

    The outer wall thickness is 2.25mm. I can't really change that due to some issues with the model, it doesn't like the curves I used.

    Thanks


    Jason
     

    Attached Files:

  5. Alex9779

    Alex9779 Moderator
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    Ok I played a bit, 50% gap fill is way too much... Depending on material I would not go higher than 20%, 10% I my default.
    I changed extrusion width from "Auto" to 0.42 or 0.44, that way "gap fill" is done and the walls should be closed...
     
  6. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Cheers Alex, I'll give it a try later.

    I increased it to 50% to try to get it to fill. I assume that only applies to infill rather than any overlapping of the outline?
     
  7. Alex9779

    Alex9779 Moderator
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    Not really...
    The percentage is not for the gap fill really.
    "Gap fill" is a own "feature" pretty much like infill. By makring the option to gap fill you activate it instead of using just perimeters for thin walls.
    Though this is not the only thing you activate and that is what the percentage is for.
    When activated S3D tries to fill the gaps either by applying an infill-like "gap fill", that's the rattling you hear when it is printing of the zigzag line you see between the walls. The other thing is that it tries to place perimeter-like lines in the wall with a maximum overlap of the percentage you set.
    If you could set it to 100% then it would print to lines on each other but extruding each line, you can image what a mess the result would look like.
    So your 50% means that S3D can fill the gap with two lines parallel to the perimeters which can overlap each other be max 50% of the line width.
    Why that didn't trigger in your case may be a bug or maybe the dimensions did not fit somehow. If you just set your extrusion width to 0.42 then you will see no gap fill but perimeter-like lines but overlapping a lot. You can roughly realize that there are two, if you reduce to 20% you can see that there are two...
     
    #7 Alex9779, Nov 23, 2016
    Last edited: Nov 23, 2016
  8. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Looking much better, I ran a handful or test pieces and found which are the best. I tried reducing the line width further and changing the overlap to 10 or 20%. The best results came from width of .38mm and an overlap of 10% or width of .40mm and overlap of 20%.

    By my estimation, three lines of .38 with 10% overlap should give a wall of: .38+.38*90%+.38%90% = 1.06mm

    Three lines of .40 with 20% overlap should give: .40 + .40*80% + .40*80% = 1.04mm

    In other words the two that looked best also give the same answer.


    DSCF0009.jpg


    Great, getting there.........


    Cheers Alex.
     
  9. mike01hu

    mike01hu Well-Known Member

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    It is a slicer problem and comes from the slicer determining that the perimeters are close enough together and will not provide an infill. There are no easy answers but I have had some success by redefining the wall thickness to be slightly thicker or reducing the number of perimeters so that the gap is recognised by the slicer. You may find that giving a greater infill/perimeter overlap will force an infill to take place as well. I trial this with a test piece that emulates the wall I am trying to produce, as most of my models have to be structurally sound. The slicer can also be upset with very thin walls where it misses them completely. Slic3r seems to handle this issue better than S3D but none are perfect.
     
  10. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Yes, getting good results now. The infill is much better too.

    Setting the extrusion width manually helped me to get finer details to print with S3D. Balancing the extrusion width and overlap helps here. I didn't have much ability to change the wall thickness with this model as it kept falling apart when I changed it.
     
    mike01hu likes this.

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