I Can't Get Rid of the Bumps on Rounded Parts
 
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sixpak66
(@sixpak66)
Member
I Can't Get Rid of the Bumps on Rounded Parts

I can't get rid of these bumps, bubbles, zits, or whatever you personally choose to call them. This started happening about 2 weeks ago - never happened before. These only happen on rounded, curved, domed parts of my prints. I researched this and here's some details of what I've tried. First, though, some info:

Printer: Creality Ender 3 S1 Pro

Slicer: Prusaslicer

Filament: PLA & PETG

Temperature: Nozzle - 200-205; Bed - 60

Wet Filament: one idea is wet filament. I have tried 12 filaments including 2 brand new ones and the results are the same - no improvement. So, I've pretty much ruled that out.

Power Recovery: I found lots of info that the power recovery could be the culprit. As you can see with the pictures of the 5 candle holders, the bumps are in the exact pattern on all of them (the white & red are hard to see but they are exactly the same as the others). They are not random. Same with the rocket. The cones are a little more random, but they were printed at the same time while the candle holders were printed one at a time in the same location. I had a print (no photo) that looked like there was a spiral staircase going around the outside of the circle part of the print. My research turned up that the power recovery saves data at certain intervals, so if there is a pattern to the bumps, that's the issue. I added "M413 S0" to the beginning of my g-code and no change. I cannot find any other way to disable the power recovery on my printer.

Temp/Speed: I've played around with these as well and no change. Other interesting things happened, but not anything I wanted.

Lead Screws: I also found cleaning the lead screws could improve print quality. I haven't done this because of the symmetry of the bumps. It doesn't seem like this work be where the problem lies.

Hot End/Nozzle: Since it was relatively cheap, I replaced the hot end and nozzle - no change.

Other Attempts: I also tried adjusting retraction setting and the extrusion multiplier, again, no change.

Again, I’ve had this printer about 6 months, and I’ve had no issues like this before. It just started happening out of the blue and I can’t find the fix. I’ve only been printing about 2 years, so, while I’ve learned a ton in that time, my experience is limited compared to many of you.

If there's any other info you need or would like to help diagnose this, I will be more than happy to provide it.

Your help would be greatly appreciated!

Thank You!

Eugene

Posted : 08/12/2023 9:19 pm
fuchsr
(@fuchsr)
Famed Member
RE: I Can't Get Rid of the Bumps on Rounded Parts

Looks like seam related. If you set the seam to aligned, the bumps should do just that, align. At least that gives us a starting point. 

Posted : 08/12/2023 11:23 pm
sixpak66
(@sixpak66)
Member
Topic starter answered:
RE: I Can't Get Rid of the Bumps on Rounded Parts

Thanks! 👍 I'll give that a try and let you know the results. 

Posted : 08/12/2023 11:42 pm
BID3D
(@bid3d)
Eminent Member
RE: I Can't Get Rid of the Bumps on Rounded Parts

My guess is y axis belt tension…looks like a mild case of layer mismatch ??

Posted : 09/12/2023 1:56 am
Zappes
(@zappes)
Estimable Member
RE: I Can't Get Rid of the Bumps on Rounded Parts

I fully agree with @fuchsr - the bumps are most likely what you get when the seam position is set to "nearest". Setting it to "aligned" should give you a straight, continous seam instead. That one can then be hidden or at least moved to a minimally awkward position using the seam painting function in the slicer.

My models on Printables
Posted : 09/12/2023 11:04 am
sixpak66
(@sixpak66)
Member
Topic starter answered:
RE: I Can't Get Rid of the Bumps on Rounded Parts

Update

Aligning the seam helped smooth things out. There is 1 line on each of the 2 elements of this model. Thank you, guys, for the wonderful advice. I still have a lot to learn.

However, I have never had a seam on any of my prints before. Is there a way to completely get rid of them?

Thanks!

Posted : 10/12/2023 5:31 am
Zappes
(@zappes)
Estimable Member
RE: I Can't Get Rid of the Bumps on Rounded Parts

Short answer: No. It's the position where the extrusion starts and ends, and there will always be a seam there. With most parts, you can hide it in some corner, and there probably are settings that can reduce it a bit, but with a filament printer, it will always be there in some form.

That being said, there is the "vase mode". In that mode, the print head doesn't ever retract, it just prints a very long spiral from the start p0int to the end point, thus avoiding the seam. The issue with that, though, is that you can have only one shell, no infill and no top layers. It's useful for, well, vases - but not much else.

My models on Printables
Posted : 10/12/2023 10:31 am
fuchsr
(@fuchsr)
Famed Member
RE: I Can't Get Rid of the Bumps on Rounded Parts

As Zappes explained, no way to hide the seam on a circular object. You can try to adjust its appearance by fine tuning Linear Advance ( https://help.prusa3d.com/article/linear-advance_2252) but like most "optimizations", I found it to be a rabbit hole where you can spend endless hours to end up with marginal improvements, that are likely to be redone for the next model that is slightly different... 

If I really need to make the seams disappear, I tend to resort to manual post processing, aka sanding and polishing.

Posted : 11/12/2023 1:25 pm
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