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Bridge fan speed surprise

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Posted · Bridge fan speed surprise

Hello community,


I've started a model which has some overhangs - 21 mm to be bridged. To do this I used the Bridge settings under Experimental tab in Cura 4.8.0.

Where comes an issue? 

I watched how the bridge printing will be done on the printer and to my surprise I saw an opposite action to what I specified in Cura.

Under "Bridge Fan Speed" I've set 100% but in reality the printer - Creality Ender 3 V2, is stopping the fan just before it starts the bridging and after finished with the bridging is going to the specified 80% for the rest of the layer, which is not overhang. It did this with the initial overhang layer and the rest 2 above it.

Not to mention the result is disaster but it managed to fill the gap - it is still printing and I don't know how bad it looks from below. I'll attach a picture when it finish.


My question is looking at my settings in the attached project file, why the fan is stoping when it has to be at full speed?




Dograma podlozhka.3mf

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    Posted · Bridge fan speed surprise

    Attached are the pictures of the finished detail. The filament is transparent and it is difficult to see on picture, but there is severe sagging from one of the sides.


    One more thing that I saw on layer 15. 


    The printing of the openings is in a random order. It starts on the first opening from the middle of the wall towards the center; then the nozzle goes to the second opening and starts from the outer diameter toward the inner side (it starts in the air - it is visible if looking from down up); on the third opening it copies the moves of the first one. After that the print continues again in the air for the first and third openings.

    I did not check "Outer before inner walls" box. So what the print order should be - first inner walls and going toward the outer ones or it is a random order?

    If the "Outer before inner walls" box is checked the print order is from inner toward the outer diameter of the openings. However on the top layers where the overhangs are at 30 degrees the print starts from outer side which here is in the air!







    Checked box.png

    Unchecked box.png

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    • 2 weeks later...
    Posted · Bridge fan speed surprise

    Hello community,


    I would like to understand what and how I specified in the settings to get the result I have. This time I've uploaded a video in youtube, so it can be seen what happens in reality.


    I went through the settings that I made but I don't see anything for the fan beside in COOLING (specified at 80%) and in EXPERIMENTAL> BRIDGE FAN SPEED (specified at 99%). In the general settings for "Manage materials" I have 100% fan speed.



    At layer 15 starts the bridging. The non hanging parts of the layer are printed as it should with the specified settings. Then starts the bridging, which is made to the settings - lower print speed and max fan (not very good result but satisfying for the project).

    Layer 16 - starts as specified on non hanging parts. When over the bridging part the print speed is lowered and fan speed goes to 0%!

    Layer 17 same as layer 16.

    Layer 18 same as layer 16.

    Layer 19 same as layer 16.

    Layer 20 all parts are at the specified settings.



    Another one thing I've noticed. At the initial - first layer, I normally am tuning manually the fan speed to 0% in order to have better bed bonding. However with this project the stringing in the initial layer was big, so with the last print I tuned the fan speed to 20% manually on the printer. To my surprise when the printing started, the printer corrected the fan speed to 0%! 


    What am I doing so to have this fan speed changes? How to control them?


    Attached are:

    - the last settings for the project.

    - the gcode.

    - the link to the video. 



    Thank you for your time.



    Dograma podlozhka.3mf Dograma podlozhka.gcode

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