Alternate the number of perimeters between layers
 
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Jan van Hulzen
(@jan-van-hulzen)
Active Member
Alternate the number of perimeters between layers

Hi,

I was wondering if it is possible to alternate the number of perimeters between layers. This may be an advantage when printing objects with holes. Sometimes the adhesion between the perimeters around holes and the rest of the object are poor especially if the object is large because the perimeters are printed first, before the infill. The objective would be to stick the infill of one layer between perimeters on layer directly above and below a layer.

ik know I could write a post processor which merges Gcode between layers but yeah, if it is already possible somehow that would be nice.

...
Posted : 19/02/2021 11:25 am
Diem
 Diem
(@diem)
Noble Member
RE: Alternate the number of perimeters between layers

Modifiers can apply different numbers of perimeters and they can be one layer thick so it should be possible.  STL files are permitted as modifiers so a carefully designed stack of layer-thick slices might have the effect you're looking for.

Cheerio,

Posted : 19/02/2021 11:39 am
Neophyl
(@neophyl)
Famed Member
RE: Alternate the number of perimeters between layers

Its not possible in the current versions of Prusa Slicer no.  Super Slicer which is a fork of PS has that ability though.  In fact its the single most used thing I use Super Slicer for.  The alternating perimeters really helps lock on the infill.

At the moment though the stable release of Super Slicer is still based on PS 2.2.  The developer is currently in the process of merging PS2.3 in though but its no where near ready/stable as yet.

So if you dont need paint on supports or the other changes from PS2.3 then you can always use Super Slicer.  They are very similar in layout and operation, although Super Slicer has lots more options you can tweak.  

Stable version here https://github.com/supermerill/SuperSlicer/releases/tag/2.2.53.4  

Posted : 19/02/2021 11:42 am
fuchsr
(@fuchsr)
Noble Member
RE: Alternate the number of perimeters between layers

I guess it is possible with modifier meshes but to do what the OP wants to do would require very precise positioning, which seems a bit arduous. I have never used Superslicer myself but I'd probably check out @Neophyl's suggestion first before embarking on the fine needle work of creating sophisticated modifier meshes.

 
Posted : 19/02/2021 1:00 pm
bobstro
(@bobstro)
Illustrious Member
RE: Alternate the number of perimeters between layers

Has anybody done any real testing of whether this really adds any appreciable strength? With the advent of features like only printing infill where needed and adaptive infill, the role of infill seems to have shifted to primarily supporting top layers and less for part strength. I'm finding that perimeters add strength as Stefan noted in his CNC Kitchen video. If a part needs strength, putting a few holes through it to create internal pillars made out of perimeters seems more effective and faster to print. I'm printing infill just strong enough to hold the top up for printing. I haven't done any structured testing though.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 19/02/2021 2:22 pm
Neophyl
(@neophyl)
Famed Member
RE: Alternate the number of perimeters between layers

I dont think anyone has Bob.  I like it because -A) its adding extra perimeters anyway which always helps and B) it does tie in the exisiting infill more as it locks it into the layers. 
As for if that infill makes a difference to the overall strength I don't know, it would seem not in the grand scheme of things but points A & B are enough for me to use it.  On my mk3 at 0.4 I tend to use 3 perimeters anyway generally so its giving me 3/4 and on my 0.6mm cr10 I use 2/3.

Posted : 19/02/2021 2:30 pm
fuchsr
(@fuchsr)
Noble Member
RE: Alternate the number of perimeters between layers

@bobstro Good point. Not sure how much hard data is out there to experimentally assess the role of perimeter vs infill. Like you, I usually define the amount of infill I use based on how much top surface I need to support. Hardly ever go above 20%, and my default is 10%. I usually go with 3 perimeters, or 1 or 2 for non functional parts. But all of this is anecdotal and not based on any thorough investigation. It would be a difficult experiment to design, given the broad range of infills and the obvious dependency on the shape of the model. Plus you need equipment to measure force, which I certainly don’t have. 

Posted : 19/02/2021 2:30 pm
bobstro
(@bobstro)
Illustrious Member
RE: Alternate the number of perimeters between layers
Posted by: @neophyl

[...] I like it because -A) its adding extra perimeters anyway which always helps and B) it does tie in the exisiting infill more as it locks it into the layers. 

Given how sensitive PrusaSlicer seems to be with the "buldge" issue, do you notice any variation in vertical surface quality when alternating perimeters between layers? 

I'd expect the newly-implemented Length of the infill anchor setting to help with adhering the infill to the walls. I wonder if printing anchors on the thinner layers (those without the extra alternating perimeter) would be even stronger? And if so, would it matter in any practical sense?

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 19/02/2021 3:36 pm
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