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Under extrustion / late layer start?  

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Simon Ljungberg
(@simon-ljungberg)
Member
Under extrustion / late layer start?

Hey,

I've got this issue with my stock (except silicon sock) PRUSA Mini where _sometimes_ on _some_ models I get this issue where the extrusion for a new layer seems "delayed" somehow. The rest of the layer prints great, despite retractions and movements. It's just these first 2-3 cm of every layer — in this particular case after a filament change, but also with a change in the model itself. I've seen this issue before in other models. And on this same model but with other filaments as well.

Slow-mo shot of issue in action

I'm still fairly new to the "deep ends of the pool" and not really sure which parameters I could experiment playing around with to try to solve this. Any ideas?

Opublikowany : 10/12/2023 3:32 pm
Simon Ljungberg
(@simon-ljungberg)
Member
Topic starter answered:
RE: Under extrustion / late layer start?

I think maybe I've figured it out, or at least I have a theory as to why it happens. The walls of the model are pretty thin and have this pattern on the outside. Because of the size the pattern causes small "holes" to exist. When I have the slicer configured to two perimeters it tries to fill in these small cavities. Leading to ~100 small dots along the circumference of the model. These are all done in one go after one another. I noticed that they weren't really getting filled in, except for the first maybe 2-3. So my theory is that during the course of trying to fill these holes the extruder is retracting more than it's extracting. Leading to the filament being further from the nozzle than the printer expects when it's time to start a new layer.

Other than changing the slicer setup to do just one perimeter so that these small dots don't get sliced I'm not sure how I would fix it. I'm perfectly happy with this solution. But I'm curious if there'd be anyway to configure the slicer/printer to handle this better? Lower the speed? Reduce retraction?

 

Image showing two perimeters and a "cog wheel pattern" filled with small dots.

Opublikowany : 10/12/2023 10:34 pm
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