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dizuane
(@dizuane)
Member
Squished/Bulged layer(s)

There’s a bulge in upper layers of some prints. At first I thought it was shifting but it goes all the way around. I’ve cleaned the nozzle and checked belt tension but can’t figure out what’s happening. This is a model I made in Onshape, but it seems the model is fine and looks fine after slicing. I’ve also tried a few different infill patterns.

Best Answer by FoxRun3D:

An object of that size and shape, I wouldn't be surprised at all to see warp, as Brian suggested. You may want to try a brim.

From the looks of it it could also be an example of the "Bulge". Search for it, dozens of pages of discussion, e.g., https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/buldge-when-print-reaches-solid-layers/  You may also have to look for the misspelling "buldge" 

However, it would be in a bit of an unusual location, a few layers higher than I'd expect to see it relative to the flat area at 25mm.

Posted : 04/02/2025 12:27 am
Brian
(@brian-12)
Honorable Member
RE: Squished/Bulged layer(s)

It's because your part warped while printing.  That area with the line is when your part peeled off the build plate. 

There are many possible reasons that this happened and many possibilities to improve it. 

In a nutshell as your part cools it shrinks.  The areas further from the print bed cool faster than the areas next to the print bed, areas of infill cool faster than perimeters or areas of solid infill.  Different thicknesses of geometry cool at different rates from other areas.  All of these things lead to stresses in your part causing it to warp. 

What material is this and what build plate did you use.  Do you have an enclosure?

Posted : 04/02/2025 1:46 am
dizuane
(@dizuane)
Member
Topic starter answered:
RE: Squished/Bulged layer(s)

Sorry, I should've included that information. Material is Overture "Super" PLA. The build plate is the standard smooth PEI sheet that comes with the MK4S. No enclosure. The profile used is the Prusa 0.20mm STRUCTURAL modified to have 3 perimeters instead of 2. I've done the calibration for the filament (temp tower, first layer calibration, and extrusion multiplier). Confirmed the extrusion multiplier is still dead-on after this print. Here's a link to the 3mf, if it's helpful - 3mf

I wouldn't have guessed that it's coming off of the build plate - once it's done printing, I still have to remove the sheet and bend it to get it off of the sheet.

Posted : 04/02/2025 2:04 am
Brian
(@brian-12)
Honorable Member
RE: Squished/Bulged layer(s)

Can you take a picture of the bottom of the part? It's usually just the corners of the partl that slightly peels up.

Posted : 04/02/2025 11:41 am
dizuane liked
FoxRun3D
(@foxrun3d)
Famed Member
RE: Squished/Bulged layer(s)

An object of that size and shape, I wouldn't be surprised at all to see warp, as Brian suggested. You may want to try a brim.

From the looks of it it could also be an example of the "Bulge". Search for it, dozens of pages of discussion, e.g., https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/buldge-when-print-reaches-solid-layers/  You may also have to look for the misspelling "buldge" 

However, it would be in a bit of an unusual location, a few layers higher than I'd expect to see it relative to the flat area at 25mm.

Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...

Posted : 04/02/2025 12:42 pm
dizuane liked
Sembazuru
(@sembazuru)
Prominent Member
RE: Squished/Bulged layer(s)

To reduce warping another option to try (I've heard people talking about it, but I haven't experimented with it myself) is to reduce the infill percentage and/or change the infill type. I've heard hypotheses that some infill types/amounts add to the force of warping. Remember, most of the strength in a FDM printed part is the wall thickness. Most of what infill is required for is to support the top of the print, so reducing the infill as much as practical will speed up print times and reduce material usage.

 

 

Or the hypothesis that excessive infill can promote warping is bunk... 😉

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Printables - https://www.printables.com/@Sembazuru
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Posted : 04/02/2025 5:34 pm
dizuane liked
Brian
(@brian-12)
Honorable Member
RE: Squished/Bulged layer(s)

 

Posted by: @sembazuru

To reduce warping another option to try (I've heard people talking about it, but I haven't experimented with it myself) is to reduce the infill percentage and/or change the infill type. I've heard hypotheses that some infill types/amounts add to the force of warping. Remember, most of the strength in a FDM printed part is the wall thickness. Most of what infill is required for is to support the top of the print, so reducing the infill as much as practical will speed up print times and reduce material usage.

 

 

Or the hypothesis that excessive infill can promote warping is bunk... 😉

No this is true, it definitely has an effect because the infill cools faster than the solid layers on the bottom of the part.  As they cool they shrink and pull on the perimeters causing the warping.  The more infill there is the stronger the pull.  Different infill patterns shrink differently. 

If you can reduce infill, add more perimeters, and a brim it should help.

Posted : 04/02/2025 6:53 pm
Sembazuru and dizuane liked
dizuane
(@dizuane)
Member
Topic starter answered:
RE: Squished/Bulged layer(s)

I've added a brim and actually went in and increased the thickness of the "wall" in the model (not the perimeters in the slice). Seems to be doing well now. I did play around with some different infills but I think the thickness I had made that wall, combined with the height it was going, had some major play in it too. I'm still learning modeling, so I expect there's some gotchas and best practices for modeling specifically for 3d printing.

 

Finally, I switched to a faster profile - and upped the perimeters of that to 3 instead of 2. I figured printing faster would get more out before cooling.. though maybe that's just me being impatient 🙂

 

Thank you all for the tips. I never would've considered a brim because I still had to pull the plate off and bend it to release it - but I suppose I only remember it being stuck and not WHERE on the plate it was stuck. Its definitely possible that the middle held on solidly to the plate while the edges where the tall wall is were loosened from the plate from cooling.

Posted : 04/02/2025 6:59 pm
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