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Initial First layer expansion Cura 4.0


phantom
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Posted · Initial First layer expansion Cura 4.0

Hi guys,

 

I've come upon a bug in "Initial Layer Horizontal Expansion"

Printed a couple of calibration cubes with setting going from 0.52mm to -0.52mm and there was absolutely no change in measurement in the cubes elephant foot, whilst this isn't a small difference ?

 

@smartavionics

Attached gcode,

Cube 1 = + value of 0.52mm

Cube 2 = - value of 0.52mm

Cube 1.gcode Cube 2.gcode

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    Posted · Initial First layer expansion Cura 4.0

    Hello @phantom, in those two files, the settings at the end of each of those files do not contain a value for xy_offset_layer_0 which is what the Initial Layer Horizontal Expansion setting is called internally. So, for some reason, you are not setting that to a non-zero value. Can you please attach the project file (.3mf). Thanks.

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    Posted · Initial First layer expansion Cura 4.0

    Sorry @phantom, those are not project files, they only contain the model and not the settings. Please do File->Save (not export!) This catches a lot of people out and I have requested that the menu gets altered to make it more obvious but the Cura developers didn't want to do that.

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    Posted (edited) · Initial First layer expansion Cura 4.0

    Hi @phantom, the answer to this little mystery is that setting the slicing tolerance to exclusive had the effect of changing the bottom layer. Setting the slicing tolerance to middle shows the missing layer which is indeed shrunk as you can see from the image.

     

    This looks like a bug to me because I would have thought that the first layer horizontal expansion should not be influenced by the slicing tolerance.

     

    Screenshot_2019-03-17_07-26-22.thumb.png.b62ffdef0235fb2a6b54819785a2ce18.png

    Edited by burtoogle
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    Posted · Initial First layer expansion Cura 4.0

    FYI, I submitted a PR (https://github.com/Ultimaker/CuraEngine/pull/1014) to fix this, don't expect to see it in Cura anytime soon.

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    Posted · Initial First layer expansion Cura 4.0

    @smartavionics

     

    Sorry for the late reply, thanks for looking into this, much appreciated !! 🙂

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    Posted (edited) · Initial First layer expansion Cura 4.0
    On 3/14/2019 at 1:17 PM, burtoogle said:

    Hello @phantom, in those two files, the settings at the end of each of those files do not contain a value for xy_offset_layer_0 which is what the Initial Layer Horizontal Expansion setting is called internally. So, for some reason, you are not setting that to a non-zero value. Can you please attach the project file (.3mf). Thanks.

    burtoogle, I have the same problem, initial layer is expanding, but I have set the expansion to -0.25 and the xy_offset settings in my gcode files say -.25. 

     

    I tried setting my initial layer really thick, thinking I was too low and squishing out the PLA, but it still expands the first layer. I can see it in the preview so it isn't a hardware problem, Cura is telling the machine to do it. Any other idea's on how to stop this expansion?

     

    image.thumb.png.2146594dd609166b8277bc36ece59010.png

     

    Don

    Face Shield.3mf

    Face Shield.gcode

    Edited by bmwbykrydr
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    Posted (edited) · Initial First layer expansion Cura 4.0

    Well that was interesting.  There were so many models scattered around in the 3mf file that for a minute I thought I was looking at my garage floor.

    "The model is not watertight".  I used the Cura mesh tools and it seemed to fix it.  Mostly though, it was buried in the build plate.

    You had Horizontal Expansion set to -.25 for the whole model and Initial Layer Horizontal Expansion set to -.25.  I don't know for sure but the net difference was probably 0 so it wasn't setting the first layer inboard.

     

    Here is how it came into 4.8.  The model kinda looks like your screen shot.

    bike3.thumb.png.91c9998bd8336bac1d350838409dde82.png

     

    This is after repairing the model and moving it up to Z=0.  The first layer is a really small patch and looks nothing like your screen shot.  Are we talking apples and oranges here?  Or...it's a Honda part and you're trying to fool me.

    bike.thumb.png.b73fac3564744de6ba0b2bdb9d305cac.png

     

    After making some adjustments to the quality settings I set Initial Layer Horizontal Exp to -1 and it looked like that worked.  Back to -.25 and that worked as well.  (That was with the model back to be half buried in the build plate just in case.)

     

     

    Edited by GregValiant
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    Posted · Initial First layer expansion Cura 4.0

    That was it! Thank you. And now seeing it, that makes perfect sense. I am not familiar with the mesh tools so I'll dive into those today.

     

    And, for the record, I moved the model down like that to print two halves and glue them together. (I got lazy and didn't want to export another STL of half the model). 

     

    That is what my garage floor looks like. You got a problem with that?! 🙂 (My wife does...)

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