I’m looking for advice on how to mitigate little bits of filament that get into the print on the “seam” specifically when the seam is set to random. This is most pronounced when I print with a PETG-CF carbon fiber filament, but I also see it to a lesser extent with regular PETG. For various reason I can’t always use an aligned seam.
And before anyone says it, this is dry filament.
Any thoughts on getting rid of these? The picture isn’t great but I’m looking at the little dots where a new layers starts or ends.
Yes, that can be a frustrating situation when this happens.
From my research in the past, the issue that causes this has to do with extrusion either being interrupted or glitching during feed. That’s the easy observation but chasing the causes can be maddening because it could be one or more of number of items.
Here is a brief list of what I found in my research but you’ll have to experiment to see which one of these might be the cause. There may be other causes I did not find so if you figure this out, please circle back and share your knowledge.
Volumetric flow set too high - Fix is either in the filament Max volumetric flow or in the speed setting in either global or object profiles
Model geometry - Stefan at CNC kitchen did an exhaustive video on how slight mathematical aberrations can cause the controller board to pause head movement if a mesh causes imprecise stepper motor movement. This should not happen in a Bambu product since it is largely an issue with past 16 bit controller boards but it is necessary to mention it. See his video for a possible remedy.
Gcode Bloat - Now this is one that seemed to make a lot of sense to me because I have experience that Gcode files larger than 10MB have failed to upload to the printer and I had to try it multiple times to get it to work. The remedy in Bambu Slicer is make sure verbose Gcode is turned off in “other”.
Here are my trouble shooting steps for what it’s worth:
My go-to option of first choice is to slow print by 50% in “quiet mode” and then option B is to go into the filament profile and change Max volumetric flow to 50% of what it was set at. You can get more granular in the speed section of the profile and limit flow that way by reducing speed but the filament profile is a quick global way to rule out over extrusion as a culprit. By default, most Bambu profiles are set to 13mm³/s for PETG and 21-22mm³/s for PLA.
Also, if you haven’t already checked, try Precise wall(Orca only) and also make sure Staggered inner seams is off. The staggered inner seams I found too problematic with creating models with flat walls such as replacement parts or tools.
And before I forget. The biggest impact on creating smooth walls I have stumbled upon has been the inner/outer wall order which by default is set to inner/outer. I changed mine permanently to outer/inner. Aside from producing nice flat walls, it also helps with hole alignment when making precision parts.
Here’s Stefan’s video at CNC kitchen. He uses Prusa Slicer to solve the issue but I believe the settings he is referring to in his example I was never able to find but truth be told, I didn’t look real hard.
Changing order of walls to outer/inner/infill had an immediate effect in reducing the bits.
Enabling “Precise Wall” also improved things to a lesser extent.
I didn’t see any difference with slowing the print down, and I didn’t want to mess with the Resolution setting so I didn’t try that.
Things have improved such that while I can still see where the extruder stopped on a line, I could not feel the tiny bits with my fingers. Previously those bits were so big I could scrape them off with a finger nail. Now the wall is smooth, even if I can still see where the little bits were. I hope that makes sense.
