Weird filament pattern extruding across model. Why?
I'm learning to use Fusion 360 and created a simple donut shaped model 85mm OD x 55mm ID x 20mm. There is a fillet on the 4 edges and 4 slots cut through the donut. There is NOTHING that crosses the hollow center of the donut. However, every time I have printed this, filament is extruded in a somewhat non-random pattern across the center. I have recreated the model twice and exported the STL files and each time the same thing happens. I've tried Slic3r 1.40.0 and Prusa Control to create the G-code. Every time the filament extrudes across the center of the donut. I have run the STL files through repair utilities and still the same thing. I'm totally confused. I even tried printing it on my older MK2 and same problem as with MK3. Printing with PLA. It is not stringing, but rather extruding the rogue filament. Any ideas?
Re: Weird filament pattern extruding across model. Why?
Hi Alan,
that looks as if the filament isn't sticking to where it should, and is cutting off the corners...
(which is interesting in a circle...)
are you by any chance trying to print external perimeters first?
with an overhang (which is what the first few layers of a fillet cause) you need to print the external perimeter last.
what layer height are you using?
bigger layer heights exhibit this behaviour more than smaller layer heights
have you tried Variable layer height? with shallow layers for the first few layers and last few layers...
are you using supports?, it looks like the outer edge of the slots are in mid air...this is likely to cause misplaced filament, but I would expect that issue to give a different fail pattern
you seem to be using a lot of infill. is that necessary?(shouldn't affect the problem that you are reporting)
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Weird filament pattern extruding across model. Why?
I guesstimated the remaining dimensions and replicated your model...
printed it on my Mk3 at 0.2mm layer height
and got similar artifacts to those you got... grrrr
I sliced the same STL for my mk2 mmu at 0.35mm layer height expecting to get a worse print... and
was surprised...
no artefacts....
the outside corners of the slots are a touch untidy. but no central crossings
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Weird filament pattern extruding across model. Why?
I re printed the same file at 0.2mm with supports and...
no central crossings
hope this helps all settings default prusa PLA (even though it was cheap chinese filament)
only the layer height modified to the largest preset thickness in each printer's case
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Weird filament pattern extruding across model. Why?
Hi Joan! You solved the mystery. I assumed that the fillet was gradual enough that it would not need any supports. I did send the STL file to Prusa tech support before I posted question here and they said the issue was a corrupted STL file, which was not the case. I was printing on fast mode with 0.35mm layer height. I think infill was like 70%.
In the past I've printed several things with gradual overhangs with no problems on my MK2. I guess with a circle it just doesn't work as well and I made the mistake to assume supports were not needed. Thank you for your help! It was driving me nuts trying to figure this out in light of Prusa support saying the issue was a corrupted STL file. Grrrrr.
Still printing but so far nothing crossing through center. : )
Re: Weird filament pattern extruding across model. Why?
Hi Alan,
3D printing is still a process in development, sometimes there can be several possible causes for similar results.
I tried a couple of other options but the areas on the outside of the slots kept failing because of their tiny contact area with the buildplate
I was looking at using variable layer height to improve the quality of the bottom radius and top radius...
but the outsides of the slots on the bottom were a problem.
not knowing what the part was designed for, I didn't spend a lot of time messing about.
I hope your model turned out well! regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK