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Confusing Bridging behaviour - Start in mid-air


tryptamine

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Posted · Confusing Bridging behaviour - Start in mid-air

I noticed my bridges always suck, even with the 'best' parameters. 

Upon closer 9inspection, i notices that the first element of the bridge is just printed in mid-air. It is the first thing Cura does in this layer: Start with the INNER part of the bridge, print it in mid-aior, then go outwards, then the normal walls.

Why is this? What can i do about it?

cura_bridge1.PNG

cura_bridge2.PNG

cura_bridge3.PNG

bridgeingBug.curaprofile

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    Posted · Confusing Bridging behaviour - Start in mid-air

    Load the model and set Cura up to slice and use the "File | Save Project" command.  Post the 3mf file here.

     

    With just the CuraProfile file, and using a model of my own, I can't duplicate the problem.

    (You might try changing what looks like "Concentric" bottom to "Lines" and see if it makes a difference.)

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    Posted · Confusing Bridging behaviour - Start in mid-air

    I think the problem is that the model has such small "landing zones" for the bridge ends.  When I set Horizontal Expansion to 0.4 everything looks a lot better.

    The author of the Calibration Shapes plugin is here.

     

    @Cuq if you could take a look at this - it does appear that the inside strings of the bridge come up short of the walls.  In this view the left end appears to be air printing.

    Are there other adjustments that can be made besides Horizontal Expansion or scaling the model?

     

    image.thumb.png.00424a39af227bab2c3d5f7bf902c0f8.png

     

    Here I've cheated and altered the model to give it some more bridge abutment on the inside.

    image.thumb.png.e32db7ea84071e77b5a265946fd322e0.png

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    Posted (edited) · Confusing Bridging behaviour - Start in mid-air

    This models is designed to be print with a maximum of  3 Wall Line Count not 5 .   If you use the recommended settings for this model you should not have this issue.

     

    image.png.f9383582573f73ed861dd66e8c44c9a0.png

    https://github.com/5axes/Calibration-Shapes/wiki/Bridge-Spiral-test

     

    3 Wall Line Count

    image.png.244fe1afdfd384a9ecd2b38654128dd8.png

     

     

     

    Edited by Cuq
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    Posted · Confusing Bridging behaviour - Start in mid-air

    @Cuq ---- are you telling me that I have to start reading instructions?  I've avoided that like the plague and I'm not likely to start going into my 8th decade.  For one thing, the fonts are too small.

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    Posted · Confusing Bridging behaviour - Start in mid-air

    image.png.72cad8344c5512fb1ef91458cdfeadb5.png 

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    Posted · Confusing Bridging behaviour - Start in mid-air
    13 minutes ago, GregValiant said:

    For one thing, the fonts are too small.

     

    Ctrl + [Scroll]

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    Posted · Confusing Bridging behaviour - Start in mid-air

    Thank you.  Now I see.

    That does qualify as another instruction though.  That's 3 in your last 3 posts.

     

    I had been using this piece of technology.  I didn't know the scroll/ctrl thingy.

    image.thumb.png.ee97e0451d4fef7c1ce10fd7db900e1e.png

     

     

     

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    Posted · Confusing Bridging behaviour - Start in mid-air

    Thanks so much for the answers.
    Still, i just can not figure out bridgeing settings that give me better quality than just brideging disabled.
    Here, first an object with bridgeingh settings as in my config file before.

     

    Secondly the same object printed without bridgeing, but with a gcode modifier to reduce printing speed to 20 at layer where the bridge is. The latter is much better.

     

    3MF of the bridgeing on file also included.



    IMG_20230111_055543_lmc_8.4.thumb.jpg.b38eb750080fe603b47e89b29102e758.jpgIMG_20230111_055603_lmc_8.4.thumb.jpg.c3b3502ad057bd80b95defbb90085616.jpg

    CFFFP_Servohalter.3mf

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    Posted · Confusing Bridging behaviour - Start in mid-air

    Things i noticed:

    When using my normal "Inside to outside" Wall ordering, the first lines of bridges are always printed into the air:

    image.thumb.png.449c7b7b95e7c6123040d40b46912a70.pngimage.thumb.png.449c7b7b95e7c6123040d40b46912a70.png

     

    The more walls i set, the more in air the first green line starts. 


    When printing with different wall ordering, things are a lot better.



    In my opinion it should be implemented that for bridge layers, wall printing always happens from outside to inside.

    I see no scenario where printing into the air as in my screenshot would be good.

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    Posted · Confusing Bridging behaviour - Start in mid-air

    Lastly:

    Even with printing from outside to the inside, bridges are still REALLY bad, much worse then without bridgeing enabled.

     

    The shell layers arte printed fine. When starting with the top-layers that build the actual bridge, always one one side threre is a retraction BEFORE the nozzle reaches the bridge wall.

    This causes one side of the bridge top to be in mid-air, which obviously is really bad:

    IMG_20230111_192605_lmc_8.4.thumb.jpg.7183abdd9832ff944d1d958a70fbb423.jpg

     

     

    To find out, where this is coming from, i first set bridge co3asting to 0, which did not change a thing.

    Then i set overall coasting to 0, still the same.


    Also my linear advance is disabled at the moment.

    What is causing this?

    BridgeBug_2.3mf

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    Posted (edited) · Confusing Bridging behaviour - Start in mid-air

    As your wall need just two lines to be print, set your Wall Line Count to 2 and it should be OK.

     

    image.thumb.png.6eae20fa8b4dd5eb13fecc19a32c0b04.png

     

    And it will not change the strength of your part.

    Edited by Cuq
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    Posted · Confusing Bridging behaviour - Start in mid-air

    Setting the walls to 2 for this model indeed helped to print the bridge at it is supposed to be printed.

    However, printing with few walls is no option for me, i usually set the wall count to 5 so i have sturdy prints and no infill showing through.

    In this case, for every print that has some wall thinner than 4 nozzle widths, briding fails completely.


    is this the case for everybody?

    Can't i get this specific print to work without having to set the wall count down?

    I do not even understand why with 4 walls as in the picture, the retraction happens too early, before the nozzle reaches the yellow wall lines. From the gcode it looks normal:

     

    image.thumb.png.08ff987e2f33884a92ccf6ea664cf6b6.png

     

     

     

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    Posted · Confusing Bridging behaviour - Start in mid-air

    You can use the Skin Overlap Value to change the overlap position between yellow and Green line.image.thumb.png.e7356f4bfdf56f7612d82f635f4865e7.png

     

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    Posted · Confusing Bridging behaviour - Start in mid-air

    even if i set skin overlap percentage to 80%, i still have the same issue: The damn bottom lines just do not attach to the walls on the right side.
    I has retract before skin enabled, disabled this and this also brought no improvement.


    I summed up the problems in a more organized way in this post:



    As this is apparently a bug in cura and should therefore be made easily accessible to more people.

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    Posted (edited) · Confusing Bridging behaviour - Start in mid-air
    26 minutes ago, tryptamine said:

    As this is apparently a bug in cura and should therefore be made easily accessible to more people.

     

    When it's a "Bug" in Cura, Cura Master, SuperSlicer, PrusaSlicer BambuLab Studio and IdeaMaker  You need to call it "Feature" and "Feature Request" 🤣

    Edited by Cuq
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