Long strings introduced by Ultimaker Cura 5.1.1

[applemaz 0]

I am attempting to print the Tree.stl file uploaded below in Vase mode with 5 bottom layers.  The circle (seen in the first photo) should be there, but those long strings are being printed across the vertices in the next several layers after the first 5 (not during the first 5 bottom layers).  They show in the Preview, but not in Prepare which makes me believe Cura is introducing these lines which print.  The second photo just shows the first 4 layers where these strings are not present as proof that after layer 5 is when they start to appear.  At around layer 34 they stop being generated and it's empty the rest of the way to the top of the tree.

 

Any idea what setting is causing this?  I need the bottom 4 layers with the open circle in the middle.  However, I don't want the strings that print.

Tree.stl

[GregValiant 1,346]

The toolpath goes from the exterior perimeter to the wall of the hole and is extruding as it makes that move.  Once the inside wall completes then the nozzle "travels" back to the perimeter and starts the next layer.  When the toolpath gets above the inside wall then it doesn't need to make the move anymore.  Both the perimeter and the interior wall are extruded as a spiral but there will be a Z-seam on both features because the nozzle leaves and then returns.

 

That's the way it works in 5.x versions.  Some folks call it a regression, but my own feeling is that 4.x versions were ignoring model features.  Your model has a 5mm deep pocket in the bottom and so it has a wall.

In Cura 5.x you can get rid of those lines by making the pocket 5 layers deep (your "bottom layers" setting).  So at 0.2 layer height if the pocket was 1mm deep you wouldn't notice the extrusions - but you won't get the inner wall either.

 

Here I've altered the model so the pocket is 1mm deep and you can see that there are no cross-over extrusions.  The wall of the hole is missing (as it would be in 4.x versions of Cura).

 

 

Edited November 16, 2022 by GregValiant

[applemaz 0]

So you altered the .stl file?  Could you attach it to this thread so I can use it?  I don't need the inner wall.  I just want this to print without the lines.  I'm fairly new to 3D printing and don't have any experience with 3D modeling software to make the change.

Edited November 16, 2022 by applemaz

[GregValiant 1,346]

I used MS 3D Builder to alter the model (it's included with Windows).  It isn't intuitive, but it's pretty good at altering STL's and at repairing models with errors.  I stuck a 41mm cylinder in the bottom and 1mm above the bottom and then merged the two pieces.

I suggest a 0.6mm line width.  Because spiralize often bounces off the Minimum Layer Time the print head will go slow enough that the high flow won't be a problem.

GV3db_Tree.3mf

Edited November 16, 2022 by GregValiant