17

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.

you are viewing a single comment's thread
view the rest of the comments
[-] 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.

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

3DPrinting

21957 readers
21 users here now

3DPrinting is a place where makers of all skill levels and walks of life can learn about and discuss 3D printing and development of 3D printed parts and devices.

The r/functionalprint community is now located at: or !functionalprint@fedia.io

There are CAD communities available at: !cad@lemmy.world or !freecad@lemmy.ml

Rules

If you need an easy way to host pictures, https://catbox.moe/ may be an option. Be ethical about what you post and donate if you are able or use this a lot. It is just an individual hosting content, not a company. The image embedding syntax for Lemmy is ![](URL)

Moderation policy: Light, mostly invisible

founded 2 years ago
MODERATORS