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BRIDGING WEIRD BEHAVIOUR


h3Lk
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Posted · BRIDGING WEIRD BEHAVIOUR

Hello everybody 🙂

 

I have realized that, at bridging, the printer does not extrude filament at the beginning of the bridge first layer. It starts extruding at "half" the bridge which, obviously, leads to a failure as there should be support on a side. Apart from this, it seems to extrude at intervals but not continuosly as one would expect it to.

 

ideaMaker and SuperSlicer do it properly so I assume this to be a slicing issue. Cura and Orca Slicer "fail" and I wonder if there is any specific setting to tune to make the printer extrude from the beginning of the bridge first layer ??

 

Thak you in advance !

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    Posted · BRIDGING WEIRD BEHAVIOUR

    I don't get that at all in the gcode.  Every line in the bridge shows as an extrusion.

    This is the first layer of a bridge

    ;TYPE:SKIN
    ;BRIDGE
    G1 F2250 X163.459 Y110 E2760.05975
    G0 F9000 X163.459 Y110.4
    G1 F2250 X130.806 Y110.4 E2760.71138
    G0 F9000 X130.806 Y110.8
    G1 F2250 X163.459 Y110.8 E2761.363
    G0 F9000 X163.459 Y111.2
    G1 F2250 X130.806 Y111.2 E2762.01463

    etc, etc,

     

    ;TYPE:WALL-OUTER
    ;BRIDGE
    G1 F1500 X164.8 Y133.07 E2730.17987
    G1 X164.8 Y108.47 E2730.58897
    G1 X131.467 Y108.47 E2731.1433

     

    You can check your gcode or load the model and set Cura up then use the "File | Save Project" command and post the 3mf file here.

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    Posted · BRIDGING WEIRD BEHAVIOUR

    Thank you for such a quick answer !

     

    I am afraid that the problem may have to do with some configuration on my side... there is extrusion but it does not begin where it is suposed to begin. It should start from a supported position and then, "build" the bridge. But it does not. The nozzle gets into the bridge area (on air) and then begins to extrude when there is no support position and I have no idea about how to correct this.

     

    AG_calibrationbridge2.3mf

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    Posted · BRIDGING WEIRD BEHAVIOUR

    I think it may have to do with retraction. I am going to compare ideaMaker retraction settings with Cura settings and see if it makes any difference.

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    Posted · BRIDGING WEIRD BEHAVIOUR

    Here is the Cura sliced preview:

    image.thumb.png.99644e2bcec4b568f18bcd9ae928589f.png

     

    Here is the preview of the gcode.  It isn't even close to being right.

    image.thumb.png.a2133ebb8cb59a9cf19f506613c32c3d.png

     

    Here is the preview but instead of that "Overture PETG" profile I switched to "Standard" and enabled the bridging and made the temperature changes.  This is the gcode preview with my changes.

    image.thumb.png.b46dd780a6a285ae05901eec327facd5.png

     

    It looks to me like something is really wonky in that "Overture - PETG" profile.  I looked at the settings and I don't see anything odd, but something isn't right.

    I think you should delete that Overture - PETG profile and start from scratch on a new profile.

     

    My question is why isn't the gcode being generated like the sliced preview shows?  I've never seen that before.  The GcodeWriter is supposed to take the slice data and write it to file.  I certainly isn't supposed to make things up along the way.

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    Posted (edited) · BRIDGING WEIRD BEHAVIOUR

    I am printing using the standard profile just to see if there is any difference...

     

    No difference 😕

    Edited by h3Lk
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    Posted · BRIDGING WEIRD BEHAVIOUR

    My gcode preview looks as the sliced one. It does not seem to be any problem.

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    Posted · BRIDGING WEIRD BEHAVIOUR

    The bottom part is sliced direct from your project file with no changes.  The top part is with my profile.

    Other than the infill (yours with gyroid and mine with grid)- I don't really see any difference.

    DSCN3127.thumb.JPG.130700a3bd0f33ff2e43208ee6fe01ca.JPG

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    Posted (edited) · BRIDGING WEIRD BEHAVIOUR

    Did you look at it while it was been printed ?

     

    The problem is, in my case, on layer 26 which does not really print. The nozzle moves from one supported position to the other and there is few extrusion on air. I would say that it really gets printed on layer 27 and above. That is what I am complaining about.

     

    The bridge starts on layer 26 and it should start from the supported position, not mid air. That is on ideaMaker and SuperSlicer.

     

    Between, thank you very much for your help as nobody else has been able to assist me on this. I am gratefull.

     

    I may try to record a video clip to show you.

    Edited by h3Lk
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    Posted · BRIDGING WEIRD BEHAVIOUR

    The printer sits at eye level right in front of me so I watched the entire thing.  It was fine and acted exactly as I would expect.

    I have written a couple of macros for Excel and so I performed a flow analysis.  All of those first skins of layer 26 are at a line width of .24 so from the actual line width of .40 that indicates 60% flow rate.  Each of the "TYPE:SKIN:" extrusions uses 0.61624mm of filament.  They are all identical so each extrusion must be exactly the same length.

     

    A video would be helpful.  Since both gcode files printed fine on my Ender 3 Pro, I am starting to suspect something might be going on with your printer.  I noticed that the project file has a retraction distance of 0.65.  That's pretty short even for a direct drive.

    This is a snippet from the gcode of your project file starting at line 4066:

    G0 X125.44 Y106.4

    ;TYPE:SKIN
    ;BRIDGE
    M106 S255
    G1 F600 X94.56 Y106.4 E0.61624
    G0 F9000 X94.56 Y106.8
    G1 F600 X125.44 Y106.8 E0.61624
    G0 F9000 X125.44 Y107.2
    G1 F600 X94.56 Y107.2 E0.61624
    G0 F9000 X94.56 Y107.6
    G1 F600 X125.44 Y107.6 E0.61624
    G0 F9000 X125.44 Y108

     

    Looks good to me.  The "Y" keeps indexing by .4mm but the "X" values are consistent and each extrusion goes from X94.56 to X125.44 and indexes over, and extrudes back to X94.56.  That is true through that entire section.

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    Posted (edited) · BRIDGING WEIRD BEHAVIOUR

    I have tried to record video but  the moving carriage makes the camera go out of focus.

     

    All that you say makes sense, at least "on paper", but the thing is that it does not work as I think it should.

     

    I will try to record the video again and see what I can come up with. You need to watch this.

     

    Edited by h3Lk
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    Posted (edited) · BRIDGING WEIRD BEHAVIOUR

    OK, I think I have got it.

     

    https://drive.google.com/file/d/1VIsOrsXYf1oYsqq5mra81yE0UWOP8K8I/view?usp=sharing

     

    In the video you can see layer 25 which is the nozzle at the supportive point, then layer 26, weird behaviour -nozzle extruding mid-air when it should be starting from the supportive point and "building" the bridge- and layer 27 nozzle printing the bridge correctly.

     

    In ideaMaker for example, layer 26 is printed like layer 27 in the video. Both layers, 26 and 27, are printed as I think they should be printed ??

    Edited by h3Lk
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    Posted · BRIDGING WEIRD BEHAVIOUR
    On 6/27/2023 at 12:16 AM, GregValiant said:

     

    image.thumb.png.b46dd780a6a285ae05901eec327facd5.png

     

    Sorry to interfere, just reacting here, I'm often facing the issue where the bridging is the worst direction possible. Is this possible to adjust it so that it uses the shortest distance, perpendicular to the one shown here ?

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    Posted (edited) · BRIDGING WEIRD BEHAVIOUR

    @h3Lk I don't get that behavior at all on my Ender.  I looks like the extruder is pushing plastic, but the end of the extrusion isn't bonding to the buttress and is simply curling up behind the nozzle.  It should be stretching across, not curling up.  It looks like the gcode is fine (and it printed fine for me) but your printer isn't executing it correctly.

     

    @Dadkitess there is a long tradition of stealing threads here.  At least yours is on-topic.

    If the lines were to go the short way, then they wouldn't be anchored to the buttresses.  The short way would pull on what are already delicate lines (inner and outer wall) and distort them - possibly severely.

    The "Top Bottom Line Directions" setting doesn't have any effect on the bridge skins.

     

    One thing I noticed is that the when a bridge extrusion touches a previous bridge extrusion, it softens it and causes it to stretch.  This causes a loop to hang down and the loop doesn't get welded to the next layer of bridge skin.

     

    I've written a plugin to change the hot end temperature for bridges.  It works fine but the walls are generally a single line of gcode so pausing to wait for a temperature change for a single extrusion isn't the best thing.

    If you want to try it, unzip the folder and put the BridgeTemperatureAdjustment.py file into the "C:\Users\...username...\AppData\Roaming\cura\5.4\scripts" folder and restart Cura.

     

    BridgeTemperatureAdjustment.zip

     

    Edited by GregValiant
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    Posted · BRIDGING WEIRD BEHAVIOUR

    Thanks for you answer, it's my bad, I was convinced that I saw a solid wall on the long edge xD

     

    The question remains the same though, if you print a "long" rectangle with the 4 walls, and hope for bridging to deal with the roof while not using any support (because... Because, it's an example ^^), I'm very often facing Cura to draw lines in weird suboptimal direction and can't change it, apart from rotating the part itself which is so weird and can't be used all the time (multiple sub optimal bridges with various direction in the same part for instance).

     

    I would really like to get an update focusing on bridging, most other slicer deals with way better.

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    Posted · BRIDGING WEIRD BEHAVIOUR

    You could write something up and put in a feature request on GitHub.  Using the other slicers as examples is fine.  One of the recurring problems I see in feature requests is that the poster doesn't really explain themselves clearly.  It's good to avoid that so a developer has a clear idea of the concept of the request.

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    Posted · BRIDGING WEIRD BEHAVIOUR
    5 hours ago, GregValiant said:

    ...the end of the extrusion isn't bonding to the buttress and is simply curling up behind the nozzle.

    It does not bond to the buttress because it is extruding "on air" where there is no buttress to bond to. If you have watched the video, layer 26 is being extruded on air and thus, it is simple impossible to bond. Layer 27 on the contrary, is extruded properly and this is why it all started.

     

    I am afraid that I will have to go back to ideaMaker since I am not able to correct this behaviour.

     

    I am really grateful for the time and effort you have put on the subject. Again, thank you very much ! 🙂

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    Posted · BRIDGING WEIRD BEHAVIOUR

    I have to go back to my point - I printed the gcode file from your project and it was fine.

    IdeaMaker might be doing something different with the bridge flow or speed that better matches the capability of your printer, but I don't see anything wrong within the Cura gcode nor with the way it prints.

    Good luck with it.  I do use IdeaMaker from time to time.

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    • Solution
    Posted · BRIDGING WEIRD BEHAVIOUR

    Fortunatelly, I have found what was causing the problem: Klipper Pressure Advance.

     

    Nothing to do with Cura. I will have to recalibrate the pressure advance value.

     

    In case there is someone having the same "problem", now you know.

     

    GregValiant: Thank you for your support. I really appreciate it.

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    Posted · BRIDGING WEIRD BEHAVIOUR

    I'll have to start asking posters if they are using Klipper.  As it gets more popular these sorts of problems start coming up.

    It's good that you figured it out (in spite of my sideways advice).

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