In this episode I’m going to tell you why this new “lightning infill” is something
you really should know about, I’m going to explain what it does, and more importantly,
why it could be perhaps the most important thing added to cura in 2021. I’m serious. It could be.
I happened by chance to notice a new version of cura the other day after reinstalling windows,
this version of cura, namely 4.12, seems quite unassuming with no loud announcements
that I’ve seen, indeed I wouldn’t have known if I hadn’t needed to reinstall,
and I do keep my eye on these things for obvious reasons.
It didn’t seem like there was much new, some stuff that seems to be for people
who own ultimaker printers, like, literally just better profiles,
whatever, but then there’s this. Lightning infill. What’s that all about then?
So, I guess they named it lightning infill because it looks a bit like
lightning but actually the more you look into it the more you
start to think that the name doesn’t really convey what it actually does.
Let’s start at the beginning. If you look at the release notes you can see a
rather uninspiring statement about high quality top layers with less material.
To me though, that’s not what’s most groundbreaking about these supports.
Wait, did I say supports? I did. That wasn’t a typo.
So the page links to a paper, and that paper is from a couple of years ago
titled “ribbed support vaults for 3d printing of hollowed objects” and while it’s not catchy,
I figure you’re at least starting to figure out what this is all about. The paper itself
is really well written and fairly exhaustive even down to giving you the code for these supports.
if you’re printing essentially either a non load bearing part like maybe an ornament,
or a prototype, or even perhaps a mould for casting, you don’t infill at all.
I agree, I think infill is often overused in situations where you could use literally none,
and perhaps I’ll make an entire video on that later.
But as we see it points out that in many circumstances you end up with what is referred
to as local minima, or to put it in plain english, bits of the model’s exterior that need support
that absolutely wouldn’t be covered by bridging because they’re lower than any part around them,
or to put it even more bluntly, printing in thin air.
Traditionally this has necessitated a very low density infill, or if you like a “stuffing” to
keep the model from collapsing in, but this of course is often only needed during printing,
once the plastic is hard - if you have allowed enough outer walls - you wouldn’t need this.
So, yes, it is basically infill as support.
The paper makes two points about this method of using infill as support,
the first being that using a coarse grid infill doesn’t work that well - and this is absolutely
true. While the slicer might add things to make it work better, like extra layers under
local minimum points for example, it’s not the ideal solution - the ideal solution would be
a denser grid to allow support close to where you’re printing in thin air. Failing
to do this causes sagging in these areas where the supporting infill just isn’t close enough.
Or, better idea, why don’t we just recognise that support infill
is a thing, and essentially calculate support backwards?
This is exactly what the paper suggests. I mean that’s literally what’s going on here. If you have
seen my previous videos on tree supports you will see parallels here, because these ribbed support
vaults are pretty much generated like branches of a tree starting with the part that needs
supporting and gradually shrinking down until it meets - get this - the internal wall of the part.
That’s the thing, because internal support structure is permanent and invisible
you don’t have to follow the same rules as you might with external supports.
You can support from any part of the model, the internal walls, another part, anything goes.
The paper then goes on to detail the algorithm which involves some gnarly maths,
but essentially that’s the overview of what this so called lightning infill is based on.
So when do you need to use it?
Essentially any time you want to print something that doesn’t need to be solid.
So that would be any of your models, trinkets, ornaments, pokemon figures,
xmas baubles, I mean this is a lot of scope because it includes things you
previously would not have considered printing hollow, because it wouldn’t have worked.
Take for example this calibration cube. It has a totally flat top, or rather, not flat enough to be
able to bridge, the slicer would have had a hard time with this, in fact that’s an understatement,
setting infill to zero here you can see cura just comes up with a bridging layer - if you
could call it that, that would just fall inside. I feel like printing this just to show you.
Actually I will.
There you go.
The hollow version uses 1.29m of filament, with 10% gyroid using 1.72m and honestly
not looking quite dense enough to me, but lightning at the same percent uses just 1.38m
and you can really see the benefit of this support...infill algorithm. The bulk of the
support is being done from the side of the object, so there’s so much less material being used here.
You can see the finished products with a gyroid on the left and a lightning
on the right, and while the claims of a better surface aren’t necessarily substantiated,
I would say because cura does a lot of work to deal with that like extra layers,
you can not really see a difference in the part and wouldn’t know that the one on the right uses
20% less material, and that’s for such a small part, scale it up and the savings become huge.
I must say that from a non practical non stress application you can’t tell it’s mostly hollow,
the part doesn’t feel flimsy either. And that’s with only two walls! Obviously larger parts may
need more walls, and there may reach a point, in fact I expect there will, where a modest
infill may result in less material usage than having several walls. So I guess that’s your one
caveat with this infill method, it’s probably not suitable for making rigid large parts.
I’m sure you can agree though, this is actually quite a big change in how we
are now able to print low stress parts like trinkets and models, and really
should have been given more fanfare I think.
So - with Christmas just around the corner, when you print all those things we always seem
to end up printing at this time of year, perhaps consider using lightning supports
and save a huge amount of material without compromising the aesthetics.
Will you use it? Comment below whether you think so or not.
I will see you next time!