Bridge detection: Weird Slicing, fatter extrudes on overhangs?
I'm getting a few weird effects trying to slice a smooth object:
Where there are overhangs, a spot will get printed with what looks like a fatter extrusion. That causes a steeper angle than is really in the part, and generates support and has the result of leaving some ugly spots/strings on the model. My otherwise good looking bottom surfaces are kinda ruined.
I've changed Z-offset because I went to a bigger 0.6mm nozzle from the standard 0.4. I had some adhesion issues but now this is making my models a little too ugly to share. 🙂
Any ideas how to prevent the fatter lines? You can see them here too on undersides (where they cause ugly surfaces that look how they do in the picture.
Oh, ah - it goes away if I turn off Perimeter Bridging Detection
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Re: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
Hi Abraham,
can you share the STL
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: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
It doesn't seem to depend on the model.
I'm using the Prusa0.6mm mk3 preset. Further experimentation shows it happening with either of the Prusa presets (0.4 or 0.6).
I played with other settings, if it happens, it follows Detect Bridging.
It is model independent - I couldn't get it for a bit on some models, but loading the settings fresh, turning on detect bridging, and slicing left me with extra bits inside of horizontal holes, for arbitrary models. I can still provide one, for instance I used
https://www.thingiverse.com/thing:1763518
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Re: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
Hi Abraham,
I am looking at the thingiverse catapult in 0.4mm profile and I can't see the artefact, even with detect bridging outlines turned on...
which area should I be looking in?
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: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
You can turn off support and it still happens. It'll be on overhangs like the hook, I didn't see it on the bowl. This is all with stock settings, as shown
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Re: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
I am no expert, but 3D printing bonds layers together by squishing them on top of other layers,
I suspect that when the printer gets to an overhang, there is nothing to squish the filament against, so it is unsquished at that point (thicker but narrower), as you can see the layer above is also unsquished.
if there were supports, the filament would perhaps be a little squished, but it won't be fully squished! (otherwise you won't be able to remove the supports. )
could this be what you are seeing?
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: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
BOY as an aside I'd sure appreciate an "auto subscribe to topics you start". Anyway, seeing this again, let's continue:
I set the support distance from "0.15" to "0 (soluble)", and as you suggested, the thickness of the line is rendered correctly.
The issue is that my prints come out looking just like the screen - a well supported underside will have big ugly bugles on it.
WYSIWYG, unfortunately. But it means if we can correct it on the screen, we can correct it on the printer, and I think everyone could get behind that?
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Re: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
I tried changing the Bridge Flow Ratio, and got the following. This is with supports off, but detect bridging on.
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Re: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
BUMP
So, is it on purpose that prints get big ugly rivers of plastic affixed to the bottom of them?
If it is, there should be an option for "how far from your STL would you like your object today?"
Not trying to be a jerk here, but this seems to be dying on the vine?
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Re: Bridge detection: Weird Slicing, fatter extrudes on overhangs?
I believe the fatter bit is explicitly showing the bridging parameters - i.e. flow at 0.95%, etc, but not compacting it as it normally would.
In other words, I suspect the weird rendering could be fixed by looking for this specific case.
That said, the prints DO come out with hanging, saggy lines where ever it shows on the screen, so just fixing it graphically wouldn't help.
I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.