Countering bulging of features behind thin walls
 
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UjinDesign
(@ujindesign)
Trusted Member
Countering bulging of features behind thin walls

Hello Prusa forum. 

Technicalities: 0.4 nozzle, printing in PETG.

Long story short, I'm trying to print this geometry (see picture) where I have a relatively thin wall with a column attached on one side of the wall. I can see an outline of the column on the other side of the wall, which I don't want. 

The strange part: I tried printing the same print with three different wall thicknesses (1.2 mm, 1.6mm and 2.0 mm). 1.2 and 2.0 showed clear bulging, but 1.6 didn't. All three wall thicknesses have two perimeters between column-infill and the wall (see other picture). 

I tried introducing smooth radii for the columns to give a smooth transition of wall thickness, but it made no difference what-so-ever. The order of which things are printed are identical between the 1.6 and the 2.0 version. 

Does anybody have any idea what on earth is causing bulging in 1.2 and 2.0 but not in 1.6?

PS: Never mind the copious amount of stringing, that's a future problem for me to solve. 

Posted : 01/03/2024 9:45 pm
Brian
(@brian-12)
Estimable Member
RE: Countering bulging of features behind thin walls

Did you try just upping the #of perimeters so that there's no infill? 

Posted : 02/03/2024 2:31 am
UjinDesign
(@ujindesign)
Trusted Member
Topic starter answered:
RE: Countering bulging of features behind thin walls

Update: I tried printing them all again on the same sheet and leaving the sheet inside a closed enclosure and letting them gradually cool overnight (I'm thinking shrinkage might be the underlying cause here). Exact same result, 1.2 mm and 2.0 mm leave an imprint / bulge, but the 1.6 mm doesn't. Very strange. 

Posted by: @brian-12

Did you try just upping the #of perimeters so that there's no infill? 

I just tried that now, and same result. 

Posted : 02/03/2024 7:59 am
Brian liked
Brian
(@brian-12)
Estimable Member
RE: Countering bulging of features behind thin walls

I can't see the whole part, but can you print it with that side on the heatbed? 

Posted : 02/03/2024 6:44 pm
fuchsr
(@fuchsr)
Famed Member
RE:

I've resigned to this being a common issue. Similar (or identical?) to the "bulge" issue (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/ ). Given that there are 30 or so pages of discussions of the bulge across multiple forum threads without answers, one would assume this was being worked on, but alas it looks like Prusa has little interest in addressing this long standing issue. Why, I don't know. Maybe most people print Ironman masks or trinkets on which it doesn't manifest itself? 

Posted : 02/03/2024 11:46 pm
UjinDesign
(@ujindesign)
Trusted Member
Topic starter answered:
RE: Countering bulging of features behind thin walls
Posted by: @brian-12

I can't see the whole part, but can you print it with that side on the heatbed? 

Thank you, but this is just a small test piece. The actual print is much larger than this! 

Posted by: @fuchsr

I've resigned to this being a common issue. Similar (or identical?) to the "bulge" issue (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/ ). 

I tried the solution there, namely enabling "external perimeters first" and... well it completely solved the issue. Hurray! 

Posted : 05/03/2024 9:25 pm
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