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What's causing this? (lemmy.world)
submitted 1 week ago by stoicmaverick@lemmy.world to c/3dprinting@lemmy.world
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About half the time recently when printing with PLA, I see that holes or loops have a line of filament running approximately through the middle which seems to be one of the inner perimeters having detached and contracted, but is still attached on both sides. Is it a temperature thing, an extrusion thing? I can't find a pattern. Bed adhesion is great. Bambu H2C, mostly printing with Bambu Basic PLA.

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[-] Blue_Morpho@lemmy.world 1 points 4 days ago

That looks like multiboard snaps. They are specifically designed for 3 walls, .2 layer height and .4 nozzle.

I had problems that looked like that from z hop. The nozzle was dragging. Enabling zhop (or increasing it a tiny bit) can stop the print head from dragging and leaving filament wisps.

[-] dual_sport_dork@lemmy.world 10 points 1 week ago

Those sections of extrusion are being pulled away from the print as the nozzle moves, because for whatever reason they are not adhering to the rest of the print properly.

Increase print temperature, reduce print speed, or reduce travel move speeds.

Also a sanity check, look at your slicer's output preview and ensure nothing about that model is causing it to freak out and attempt to print in midair...

[-] stoicmaverick@lemmy.world 4 points 1 week ago

I'd considered raising the temperature a little to get the perimeter to stick better to its neighbor, but I wasn't sure if hotter printing would worsen the thermal contraction, which is what I was originally suspecting was happening. Nothing ever pulls off from an outer perimeter, it's only inner perimeters of empty loops or holes.

[-] HelloRoot@lemy.lol 3 points 1 week ago* (last edited 1 week ago)

Nothing ever pulls off from an outer perimeter, it’s only inner perimeters of empty loops or holes.

Isn't that obvious?

Try making a circle of a certain size on a flat, empty table, by dragging a string. The circle will become smaller, than the target size because of the part that is already laid down will be dragged inwards.

Now drag the string around a gluestick, it can't be smaller than the gluestick's circle because the gluestick is in the way.

[-] dual_sport_dork@lemmy.world 1 points 1 week ago

Your nozzle won't travel anywhere outside of your model's outer perimeter because it has no reason to (unless your g-code is super borked, see my comment about your slicer above) but it will be dancing around within the space between the outer perimeter and center of your model many hundreds of times. Any extrusions pulled off on the outer perimeter would stay somewhere within the model.

[-] stoicmaverick@lemmy.world 1 points 1 week ago

Not quite sure what your concern is with the top fill pattern. It is a load-bearing part, so it kind of needs to be the way it is to retain the part coming out the other side. As far as the extruder exiting the perimeter of the model, I would remind you of the possibility of printing more than one model on a build plate. Although, I hadn't yet considered trying to print only one to see if it still happens, as a troubleshooting approach. I'll try that later, to rule out the possibility that it's being mechanically pulled off by an extruder transport move.

[-] dual_sport_dork@lemmy.world 1 points 1 week ago* (last edited 1 week ago)

Unless you've deliberately reversed your walls/infill printing order, the default is to print walls first. Your print head and nozzle won't have any reason to leave the perimeter of the model even if you're printing multiple examples of the part until the entire layer is complete on one of them. It will move to the next part in the array only after finishing the infill, which is well after your problem may have occurred on either the inner or outer perimeters on any particular layer.

I'm not sure what you're on about with top fill. I didn't say anything about your fill pattern or percentage.

[-] nullroot@lemmy.world 4 points 1 week ago

You're sure it's the first layer as well as others? The print bed side looks pretty cleanly pressed against the build plate, it seems unlikely you'd have issues unless there is some major deviations in your bed leveling. It mostly looks like the gcode had it try to print in the air/with nothing for it to stick on.

As others have pointed out this is pretty common for inner circles and you may have to find a way to tweak the print settings or the design to be more printable. You can look through the preview layer by layer and check the tooling path for anything that would obviously not work.

That being said, if you'd like to share the 3mf file I wouldn't mind poking at it later... 3mf is what Bambu slicer uses isn't it?

[-] Imgonnatrythis@sh.itjust.works 3 points 1 week ago

Try enabling avoiding crossing perimeters in slicer.

Check nozzle cleanliness - remove any junkus from outside.

See if slower print speed helps?

[-] MeowWeHaveAProblem@toast.ooo 2 points 1 week ago

Is the room temp high enough with no cold drafts? I live in a cold area and have had print problems with the room being to cold.

[-] stoicmaverick@lemmy.world 2 points 1 week ago

It's enclosed

[-] thisbenzingring@lemmy.today 1 points 1 week ago

it's not being adhesive, trying a 5+ degrees might help. try setting drawing the outside parameters first.

[-] stoicmaverick@lemmy.world 1 points 1 week ago

It's both first layers and higher. No pattern I can find. Bed adhesion is definitely fine, I haven't had a single lifted corner since I started using the SuperTac plate.

[-] thisbenzingring@lemmy.today 1 points 1 week ago

the pattern is pretty wonky, your slicer isn't doing you any favors. try a different top and bottom pattern if the other suggestions don't do anything

[-] PhatalFlaw@lemmy.world 1 points 1 week ago

It looks like that's your first layer? Poor bed adhesion coupled with a slight under extrusion might be doing it. You could also try to slow down your first layer dramatically (50% or more slower)

[-] stoicmaverick@lemmy.world 1 points 1 week ago

It's both first layers and higher. No pattern I can find. Bed adhesion is definitely fine, I haven't had a single lifted corner since I started using the SuperTac plate.

this post was submitted on 05 Mar 2026
17 points (100.0% liked)

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