A part cooling fan is something which has
become a necessity on our 3D printers since the days we started printing parts in PLA
or similar materials. But does this cool stream of air that helps
us print very detailed models maybe reduce the strength of our parts? This is exactly what I’ve tested for todays
video and we’ll also learn how different fan settings change the accuracy of our printed
parts, using a 3D scanner! Let’s find out more! Guten Tag everybody, I’m Stefan and welcome
to CNC Kitchen! This video is sponsored by Audible. When the first RepRap printers emerged in
the homes of makers the material of choice was usually ABS where cooling the printed
material down too quickly will cause layer separation and is therefore not really wanted. Only after materials like PLA have been becoming
more and more popular, fans that rapidly cool down the printed material were needed to print
fine details and overhangs. In contrast to ABS, PLA also doesn’t have
the tendency to crack between the layers or to separate from the build platform when being
cooled. Nowadays people seem to even challenge themselves
to get the most amount of cooling for their printers. But this raised the question for me if too
much cooling could actually be detrimental for the strength of our 3D printed parts because
it reduces the temperature of the previous layer and gives the new material less time
to bond together. If you have ever watched one of my filament
test videos, you might know that I usually print two of 3DMakerNoobs temperature towers
where on one I vary part cooling in steps and then chose the one with the lowest amount
of cooling but still good print quality. This is because I always assumed that less
cooling also means better layer adhesion. Though, I never tested this assumption in
a controlled manner, so this is what we’ll do in today’s video. This video is actually one part of a video
series where I want to test the influence of different settings on the strength of our
3D prints, with the goal of finding a combination of parameters for maximizing the toughness
of our parts. If you don’t want to miss that, then make
sure to subscribe to the channel and ring the bell to be notified of upcoming videos. Due to popular demand I won’t be focusing
today’s tests solely on PLA, but also included PETG. Unfortunately, this material caused me quite
some trouble as you’ll see later and I actually had to redo all the tests with a second filament
brand. This is also where today’s sponsor Audible
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of your audiobooks forever if you, at some point decide to cancel the service. Thank you Audible for sponsoring this episode! I usually test the strength of 3D printed
materials with these dogbone tensile test specimens that I print at 100% infill in a
horizontal and vertical printing orientation. The horizontal specimens tell us how strong
the base polymer is, because we load it in printing direction where we don’t have layer
lines reduce strength. The vertical specimens on the other hand test
exactly the opposite and this is how good subsequently printed layers stick together. Ideally the strength would be similar but
the strength of the standing specimens is usually at least 50% lower. Unfortunately, these specimens gave me quite
some trouble in the past because if the two mounting yaws of my test machine don’t align
perfectly, the coupons will see a slight bending load instead of pure tension and therefore
fail prematurely and invalidate the results. For this reason, I designed a new set of samples
that feature half spheres on both ends and which are still nicely printable. With the suitable sleeve and holder they form
a spherical bearing and minimize bending loads on the samples. This greatly reduced the scatter in my results
and will be the new shape I’ll use for layer adhesion tests. For this series of tests, I’ve printed 3
samples for 5 different fan settings which makes 15 samples in total for each of the
materials. The fan settings I used were 0%, 20%, 40%,
60% and 100%. I printed all of the samples in a single print
job where each group of samples was finished one after another. In order to compare the strength values at
different fan settings to a baseline, I also printed 3 horizontal dog bones but these ones
only at one single fanspeed since I boldly state that there won’t be a significant
change regardless of the cooling. Please bear in mind that these set of results
are probably not 100% true for any other filament manufacturer and printer, because slight changes
in the setup can have a big impact on the results. So, use this more as a guideline and look
at the trends. I printed all of the samples on my Original
Prusa i3 MK2.5 at a layer height of 0.15mm with 2 perimeters at 100% infill. At the time of printing it was summer and
I had between 26 and 27°C in my office. I printed the samples in SpoolWorks PLA, DasFilament
PETG and PrintaMent PETG from Aprintapro. In general, the parts looked nice, you were
only able to see that the parts with no cooling did show some problems in the overhanging
regions. Let’s start with the test results of the
PLA parts that I tested one after the other on my self-built Universal Test Machine. The baseline that I printed lying, which should
represent the ideal and maximal material strength failed at 59 MPa with only very little scatter. Next we come to the layer adhesion samples
where the ones with 100% fan speed failed at 30 MPa, so only half of what the horizontal
coupons were able to bear. At 60% and 40% fan the results were only slightly
better with 31 and 33 MPa of tensile strength. At only 20% cooling fan we can see that the
layer adhesion already improves and the specimens failed on average at 38 MPa with is already
64% of our baseline. Lastly, we have the samples that were printed
with no cooling fan at all and those were able to bear an astounding 48 MPa which is
over 80% of the reference! This shows that we can increase layer adhesion
by more than 50% by decreasing the amount of cooling we use. Next I tested DasFilament PETG. The tensile strength of the horizontal specimens
was 53 MPa with basically no scattering at all. I won’t go through the rest of the results
though, because they were all over the place and something was extremely wrong with them. There was no patter recognizable and the strength
test results were more or less random. I’ve been printing a lot with this material
over the last years and was usually very happy with it, but here either the material or my
printer had quite an issue. As I already said in the beginning, I didn’t
want to leave my results like this so I took the time and printed another set of samples
in PrintaMent PET-G from Aprintapro. The sample looked really nice and very well
extruded because they still kept a kind of translucent look after printing. The baseline tensile strength was slightly
lower than the one from DasFilament with 49 MPa. Again, there was basically no scatter between
the tests. The layer adhesion strength of the PETG when
the fan was 100% on, was around 21 MPa which is only 42% of the baseline and therefor worse
than what we have seen with PLA. 60%, 40% and 20% were all in the same region with 26
MPa of ultimate strength, which is an improvement but still not too well. Only the samples printed with no fan at all
were able to bear almost 41 MPa before they failed which is only less than 20% lower than
our baseline and therefore very impressive! The results kind of confirm what my suspicions
were in the past. PETG still seems to be a bit more tricky to
print and therefore the results scatter more. Secondly, the material should be printed with
less than a full cooling fan, because this increases strength but the print quality,
as we will see in a minute, still remains very nice even at settings below 50%. For both PETG and PLA we have seen, that the
layer adhesion is always significantly lower than the base material strength. Still we can influence the adhesion with the
amount of cooling we use and less is usually better. In order to check the influence of part cooling
on print quality I have also printed several 3D Benchys at fan speeds of 0%, 20% and 100%. Ideally, I want to go as low as possible with
cooling but at some point the prints really start to look horrible. Both PLA and PETG prints without any cooling
looked like they were melted in the sun and I did already increase the layer time to over
20 seconds. That’s actually a setting which can help
you print nicer at lower fan settings because it will slow down your prints when a layer
takes less than 20 seconds, increasing the natural cooldown time. Chuck from Filament Friday even stated that
you can print PLA without any fan at all but he was using an Ender 3 for his tests. The thing is that all of these CR-10 variants
have a horrible fan shroud design where the fan that cools the heatsink also directly
cools your hotend and the print. So 0% fan on such a machine is still some
cooling and will decrease layer adhesion. The Prusa on the other hand has two totally
separate cooling paths where no cooling air from the heatsink touches the print and therefor
0% part cooling fan also means not cooling at all. That’s also quite important for higher technical
materials like Nylon, PC or even ABS. Just keep that in mind. I currently have a professional 3D scanner
from the company GOM at my disposal that I can use for a couple of weeks for my research. For this reason, I also scanned all of the
3DBenchys to find how they really deviate from the ideal geometry. I had to coat the translucent PETG prints
with some chalk spray to make them scannable. For the comparison of scan to reference geometry
I used GOM Inspect which can actually be downloaded and used by anyone for free. I will show you a couple of deviation plots
in a second. The way you read them is pretty simple. The color is a measure of the geometrical
deviation of the real scanned part to the nominal STL file. Blue is negative and this means that the real
part is smaller or inside the reference. Red means a positive deviation, so the scan
is outside of the reference, so basically more material at that location. Now to the results. I guess for the prints without any cooling
fan we don’t really need to talk about deviations, because especially the PLA one just looked
horrible. The thing that was interesting to see though
was, that you can clearly see the sagging of the horizontal surfaces on the PETG part. The parts with 20% cooling already looked
way better and the PETG one was basically looking perfect and you almost can’t see
any quality problems even at this low level of cooling. The PLA Benchy at 20% cooling is even more
interesting because it looks okay from one side but the other side, which is the side
facing away from the part cooling fan is totally deformed. So it seems as if 20% cooling with Prusa is
still on the low side and it might be an interesting project to optimize the fan shroud so that
it’s more even in all directions. If you guys are interested in that topic there
is actually a cool blogpost from Nophead, the father of the Mendel90, on the uniformity
of different fan shroud designs. I’ll leave a link down below! Both of the 100% prints look perfect on first
glance, only the 3D scans reveals that there was some deformation in the highly overhanging
areas. So nicely printable doesn’t always mean
geometrically accurate. If you by the way have other project ideas
I could do with this 3D scanner from GOM then leave a comment down below! In summary, what have we learned? So I think we have nicely shown that the layer
adhesion of FDM parts is significantly influenced by the amount of cooling air that is used. Less cooling usually means better layer strength. Unfortunately, at some point the looks of
our prints is influenced and at low cooling values print quality suffers. PETG is better in this regard than PLA. If you want to improve your part-strength
than play around with the amount of cooling and find the lowest setting possible with
still sufficient part quality. Slowing down your print and using minimum
layer time will help you with print quality. Also, the experience with the first PETG samples
showed me again how unpredictable 3D prints can actually be. Without proper quality control measures our
3D prints shouldn’t be used in safety critical applications. But what do you think? Was this something new for you and how are
you handling layer adhesion problems? Also let me know what other print setting
you’d like to see me test in the future! Leave a comment down below! Thanks for watching everyone. I hope you’ve learned something new today. If you did, then leave a like and make sure
that you’re subscribed for upcoming videos. If you want to support my work then head over
to Patreon or help me out in other ways. You can also support the channel and get a
free audiobook if you visit audible.com/cnckitchen or text CNCKITCHEN to 500500 and sign up for
a 30 day free trial. By the way, also check out the other videos
in my library! There are more you might like. Auf wiedersehen and until next time!
He has a bunch of really good videos. He also looks at strength across the layers with layer thickness for instance.
I've been printing some brackets in PETG with 5 perimeters, a 1.0 nozzles, and 0.4mm layer height. They are silly strong. Another CNC kitchen video he did a DOE to test the strength of layer heights and appx 40% of nozzle diameter is the strongest. I'm a quality engineer during the day so his statistical approach is very satisfying.
I found this video, and since strength is a major concern it seems useful.
Or, use as much cooling as you want and use salt annealing after the print for even better strength.
I don't cool anything unless it's an overhang or a bridge. any vertical section can be left uncooled without loss of quality