When you prepare a model for 3D printing you'll always need to choose an infill structure
for your part.
Since current slicers give you the option of choosing between a whole lot you might
have already been asking yourself which one is the strongest and most suitable for your
application.
So in todays video we'll crush some test samples to find out which performs the best
and I was especially interested in the much hyped gyroid infill you might have heard of.
Guten Tag everybody, I'm Stefan and welcome to CNC kitchen.
In a previous video I've already been taking a look at the strength of different infill
structures that you can find in Simplify3D and also talked about why it is more efficient
in many cases if you increase the number of perimeters instead of increasing the infill
percentage.
If you haven't seen it yet, there is a link in the description.
I wanted to do a bit more research in this direction and especially find out how different
patterns behave in different directions, because often you can't orient your part in a way
that it is perfect for the chosen infill.
In addition, Slicer Prusa Edition features 3 3 dimensional infill structures, most prominently
gyroid infill, that claim to have more isotropic, so more uniform strength behavior in all loading
directions.
In order to perform the tests for this video I had to adapt my tensile testing machine
in order to be able to perform compression tests.
If you are interested in the machining process on my CNC there is also a link in the description
to that video.
I've been thinking for quite a while about a suitable test specimen.
At first I thought of just printing the infill pattern without any exterior walls but since
the infill in your parts will always be surrounded by a shell of material which is reinforcing
the structure I ended up printing cubes of 22mm side length that use 1 perimeter and
3 top and bottom layers at 0.15mm layer height which results in a constant wall thickness
of 0.45mm.
This gave me the possibility to use the same specimen for the tests where I crushed the
blocks from the top as well as from the sides and therefor make the results more comparable.
I'm well aware that this shell will add additional strength to the structure, so we
are not purely testing the infill, but since it is the same for all we can still compare
results.
I haven't tested all of the patterns available and tried to concentrate on the, in my opinion,
most relevant ones which are Rectilinear, Grid, Triangle, Cubic, Line, Honeycomb, 3D
honeycomb and Gyroid.
The way how the parts will probably fail in such a compression test is usually not compressive
yielding of the structure but the stability failure buckling of a wall which then leads
to more load on the rest of the part and therefore fatal failure.
The shape of the infill or even how the infill supports the external shell will determine
how and at what load the structure fails.
The slenderness of the structures will play a huge roll and curved structures like for
example in the gyroid will act like ribbing and improve strength.
I am a little limited by my test machine, because it unfortunately stalls at around
3.5kN or 340kg of load so I only used an infill ratio of 10%.
Unfortunately as I also already talked about in a previous video, 10% infill does not results
in the same amount of material used for each of the samples.
Most notably a part with 10% 3D honeycomb infill weights almost double one with 10%
rectilinear infill.
Either that's a bug or the generation algorithm is strange.
Anyway, so at first I printed a batch of samples, all at 10%, weight them and then adjusted
the infill ratio slightly so that all samples roughly weight the same in the end that I
used for testing.
Before we take a look at the strength of the infill patterns lets at first take a look
at the printing time, because this is also something that is well relevant.
Most of the infill patterns take around the same amount of time to print, only the honeycomb
structures take way longer due to the constant change of printing direction where the printhead
has to accelerate and decelerate constantly which wastes a lot of time.
Also at least I have the fear that my printer rattles itself apart after a while when I
use these patters.
Interestingly, the gyroid infill, that also consists out of a lot of tuns, doesn't take
much longer to print than the other more standard patterns due to the nice, smooth turns that
the printhead does, where accelerations are much smoother so a kind of constant line velocity
can be kept.
I printed all of the samples in Formfuturas Premium PLA on my original Prusa i3 Mk2s.
Now let's come to the destructive tests.
I've been testing each patter once in the build direction and once from the side.
Let's start with the pattern I mostly use for my prints which is rectilinear infill.
The first sample failed at 309 kg of load whereas if you load it from the side, it was
only able to bear 191 kg, which is almost 40% less.
Keep in mind that these samples are only 22mm in each dimension, so this amount of load
is already quite impressive.
Unfortunately, the cubes of the Grid, Triangle, Line and Honeycomb patters were too much for
my machine and it stalled for all of them at around 350kg of load.
Taking a look at the samples still already showed that they were just before failing
because the outer walls already showed buckling marks.
So for these samples we don't really have an exact value to compare against but if we
still look at the transverse strength the other loading direction is at least 30 to
45% weaker.
The interesting results are now the 3D infill patterns where all performed very comparable
in the Z direction.
If we also take a look at the strength 90° rotated, cubic and gyroid infill perform exactly
the same just as claimed only the 3D honeycomb performs about 15% worse.
So which is now the best infill you can chose.
Well, that depends.
I'm still a huge fan rectilinear infill if your parts don't require a huge amount
of strength.
It prints almost the fastest and it's the infill that has the densest structure which
is great for your top layers so reduces pillowing even at low infill ratios.
If we take a look at the numbers, the line infill pattern might even be better, since
it has higher strength values, prints faster and the infill spacing is almost as dense
as with rectilinear.
If you have a part that is purely loaded in compression honeycomb might still be the way
to go, but prints quite long and might rattle your printer apart.
Triangle infill might be an alternative, maybe a little weaker but prints much faster.
For the 3D infill patterns, 3D honeycomb is dead in my opinion.
Cubic and Gyroid infill perform pretty much the same just the infill spacing is a little
denser with the new contestant and come one, it definitely looks cooler.
So in summary, I probably might be using line infill for any esthetic parts and quick prints
in the future and anything that will see some load, Gyroid infill will be my new way to
go due to its good and uniform strength in all directions.
Now I'd really like to know from you guys if I've missed something and which investigation
you'd really like to see in a future video, just leave a comment down below.
I hope you like the video and learnt something.
Please leave a thumbs up.
I spend quite a lot of time in my research, so if you want to support the making of these
videos than consider becoming a patreon and take a look at the affiliate links down in
the description.
Subscribe to the channel if you haven't and take a look at my other videos.
Thanks for watching, auf wiedersehen and I hope to see you around next time.
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