Weird bumps are printed in specific places where an overhang occurs

[Schmordan 4]

I'm printing on my Ender 3 V2 with a 1.15 mm layer height and on the file attached, it consistently created these weird bumps on the outer walls.

 

It's really annoying, as I want a perfect surface for this, as it's a case, and it happens with some other STL files as well. along with the bump problem my printer also make these weird rings that look like small layer shifts.

I'm printing at 190℃ for the nozzle and 65℃ for the bed.

 

The file:

airpod_case_l.stl

[Torgeir 243]

Hi @Schmordan,

 

This often happen when printing objects that's have overhang starting close to the heat bed, as heat is radiated from the bed close by. Can be a problem cause the cooling fan may be shadowed by the object in certain angles.

This can be a tricky problem to solve, but printing with blue tape and heat bed off work well for me.

 

Thanks

Torgeir

 

 

Edited June 18, 2023 by Torgeir
Text edit.

[Schmordan 4]

Sorry for replying so late @Torgeir,

 

i've printed the 'Mini-Me V4' fan duct upgrade for my printer to upgrade it's cooling. This has helped the overhangs some bit but i've changed so many settings like retraction and temperature that i don't know what fixed the issue.

Still, i'm happy that it worked!

my retraction distance is now 6.3, my bed temp is 55 and my nozzle temp is 195. this seemed to stop the overhangs from drooping. i think the bumps were caused by the sharp edges of the print curling up because of the high temp, so doing all these upgrades helped.

 

I'm still confused why Cura keeps changing the wall ordering though, and it keeps creating those rings. 😕 

 

Thank you for your suggestions!

[Schmordan 4]

It seems that these rings only occur when there’s a ledge, hole or gap that’s being printed. 

the order switches from outside-to-inside to inside-to-outside (what’s meant to be printed). The latter of the two makes the print look more shiny, unlike when it’s printing inside-to-outside, so the rings are very noticeable.

 

does anyone have any idea how to fix this, or why it’s happening?

 

thank you!

[Torgeir 243]

Hi @Schmordan,

 

Thanks, I'll got plenty of time, so no problem.  🙂

That's good information, lets see how to improve.

 

The overhang this model have this close to the bed is quite extreme, -as I have an UM2ext+ having two cooling fans and sure this will be something to struggle as well with this printer.

 

If you send your project file someone have a look at the settings (see menu "File" then select "Save Project").

A project file contains - Cura version -all the setting, your model and printer type.

 

Thanks

Torgeir

 

 

[Schmordan 4]

Update: 

sorry for disappearing for a year, but i found a Cura profile for a 0.12 mm layer height made by CHEP (linked at the bottom) and fixed the issue. i think my profile was just a little wack, as i had modified it so much in the early stages of my printing. i also think the rings caused by Cura have been solved in the later updates that they've released, so that's great.

 

 

(https://thangs.com/designer/CHEP/3d-model/Ver3.6%20Cura%20V5.0%20Filament%20Friday%20Best%20%280.12%29%20Profile%20by%20CHEP-1002033)