Bridge Infill, Perimeters and Height Range Modifiers suggestion
 
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Durahl
(@durahl)
Trusted Member
Bridge Infill, Perimeters and Height Range Modifiers suggestion

Greetings

Today while fiddling around in Slic3r I came across an idea regarding Bridging and Perimeters...

My issue lies with the, light blue colored, first Bridge Infill layer after the Internal Infill ( I removed the Internal Infill in this example ).
If all works well then, this layer will just barely touch the yellow Perimeter and everything's fine but often enough it doesn't and then either curls up or down which depending on how bad it does that can either cause bumps in the following layers or in some cases cause prints to fail.

So, I tried to modify that particular layer with a reduced perimeter Height Modifier in hopes of causing the Bridging Infill to expand ONTO the Perimeters below it instead of just aligning itself NEXT to the ones on the same level.

Alas I couldn't get it to work like that ( the GIF above is a mockup ) as Slic3r would simply raise the Bridging Infill to the next available Layer with the default Perimeter setting and again print in thin air so yea... Would this maybe be a feature worth picking up by default for as long as there's at least two Perimeters ( Perimeter + Outside Perimeter ) available?

Posted : 05/12/2020 10:20 pm
Neophyl
(@neophyl)
Famed Member
RE: Bridge Infill, Perimeters and Height Range Modifiers suggestion

All suggestions need to be made over on github for Prusa Slicer.  https://github.com/prusa3d/PrusaSlicer/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc

Its a decent suggestion which is why it and several others have been added to Super Slicer which is a fork of PS.  It can have extra perimeters on alternate layers.  This ties in all the infill to the walls much better.  I use it all the time.  Super Slicer also have various options for doing a dense infill on the layer just below those you are picturing so it stops that sagging you mentioned.

Posted : 06/12/2020 12:53 am
Vojtěch Bubník
(@vojtech-bubnik)
Admin
RE: Bridge Infill, Perimeters and Height Range Modifiers suggestion

> Its a decent suggestion which is why it and several others have been added to Super Slicer which is a fork of PS.  It can have extra perimeters on alternate layers.

This is a trick introduced in Kisslicer as "fractional perimeters". That may or may not help in this case. It will help if the additional perimeter is drawn below the first dense (bridging layer). If you are not lucky, it will actually make things works if the additional perimeter is added at the bridging layer.

> Super Slicer also have various options for doing a dense infill on the layer just below those you are picturing so it stops that sagging you mentioned.

SuperSlicer has some experimental methods of drawing straight segments or perimeters on the open side, but that will not help in this case at all, as the problem is binding to the inner perimeter.

So @neofyl 's universal advice to try SuperSlicer may not be the best one here, as if the "fractional perimeters" are enabled, in 50% of cases it will likely make the situation worse. If it improves the bridging in your case, it is by accident, not by design.

> Alas I couldn't get it to work like that ( the GIF above is a mockup ) as Slic3r would simply raise the Bridging Infill to the next available Layer with the default Perimeter setting and again print in thin air so yea... Would this maybe be a feature worth picking up by default for as long as there's at least two Perimeters ( Perimeter + Outside Perimeter ) available?

This actually a general issue of bridging: It works if there is some infill are below to anchor the bridges to. Your proposal is natural, but it requires lowering the number of perimeters, which may not be what you want in regard to mechanical properties of the object: Indeed, the perimeters have significant influence over the print strength.

...
Posted : 06/12/2020 6:15 am
Durahl
(@durahl)
Trusted Member
Topic starter answered:
RE: Bridge Infill, Perimeters and Height Range Modifiers suggestion
Posted by: @vojtech-bubnik

Your proposal is natural, but it requires lowering the number of perimeters, which may not be what you want in regard to mechanical properties of the object: Indeed, the perimeters have significant influence over the print strength.

Mhh... I'm not exactly seeing the issue with my proposal in terms of Perimeter strength... The material is still there that would normally be the Perimeter but in this case it's part of the Bridge Infill. My example with the Bridge Infill reaching into the Perimeter by two of four was maybe excessive where 1 of 4 would pretty much suffice with the issue.

Strangely enough! PS Actually DOES what I wand by default UNDER CERTAIN conditions as seen below:



PS being kinda unpredictable with this particular feature is a tad infuriating 😐

I also so just to happen to have 3D Printed a piece that, while not the same, is having a very related issue with the Bridge Infill being formed very unfortunately in PS and consequently also ending up terrible on the actual 3D Print.


The entire Bridge Infill layer could have been a continuous layer but for whatever reason PS decides to single out the area above where I'm planning to insert the Magnets and while THAT section works out fine the remainder turns out terrible.


Is there maybe a global setting that can deal with this? Alternatively, a Height Range Modifier one?

Posted : 06/12/2020 5:54 pm
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