So, what if there's a way to print TPU at the same speed or faster than you already print PLA?
In this video I will show you how I managed to do this,
and how I managed to actually improve quality at the same time.
-- intro ---
Are there really TPU cheat codes? Well, honestly, kind of - inasmuch as a set of
rules that you can follow to dramatically increase your quality and reliability
when it comes to printing TPU on a bowden style printer like the ender 3, 5, and so on.
But they're not magic of course, this is about understanding the intricacies of printing
TPU and leveraging it to your advantage. If you haven't seen my first TPU video then
add it to your viewing list and check it out after this, a card should appear about...now for that.
OK then, we've got a lot to cover in this video so strap in, let's go.
pressure ==========
flexible materials are flexible, the hint is in the name honestly, but if you imagine trying to
push an elastic band down a tube and expect to be able to control how much comes out the other end
then you get the idea of what we're up against when printing TPU.
Of course a lot of the process is engineered to make that work better,
for example the tube in question is made of PTFE
which is one of the slipperiest materials known to man, and the width of the tube is
practically the same as the diameter of the filament giving it nowhere to hide.
If we have a look at this badly drawn representation of a bowden setup you can
see the general process, the point I want to make here is that you have a setup that works almost
like a hydraulic system because the filament is liquid at the business end, and so if you
think of it that way then you have a large cross section at the extruder where you are applying the
force - effectively 2.4 square millimetres, and at the liquid end you have a cross sectional area
on a 0.4mm nozzle of 0.13 square millimetres, so from what I remember of science, that means
around a 20 to 1 ratio between the extruder and the nozzle.
Now, importantly, pressure is the enemy of flexible filaments, or rather excess
pressure is the enemy. Too little pressure and it will just compress inside the tube, but too
much pressure build up while printing - which is the more common problem in a bowden setup - will
eventually cause a failure, as in the diagram the first weak link in the chain is the extruder,
so you get filament popping out, looping round the gears, or being ground up.
It's actually a sign of a problem, not a problem itself. If your filament is doing this,
it's kind of an emergency pressure valve, a sign that you should manage the pressure better.
So - Well, one thing we can do to lower the pressure that we're going to look at today
is that nozzle cross sectional area. So yes, in a way this was a really long way
of asking if a 0.6mm nozzle will enable us to print TPU faster and with less errors.
I just think it's important to explain why, as well as pose the question.
mini delta. ===========
I want to introduce you to the monoprice mini delta. If you are subscribed to dr
vax's channel...he's changed his name but that's what I remember him as,
then you will already have seen this printer. In fact they've released a new version.
The monoprice mini delta is to printers what a hammer is to precision machine screws.
With absolutely no bed levelling and a bowden extruder that would work better on TPU if you
had the tube sticking out the side where it invariably spits it, these machines are
ideal to test our theory out. Don't worry, we'll get to the Ender printers in a bit, humour me.
I'm fitting one of my deltas with a 0.6mm nozzle and the other with a 0.8mm.
I'm already well aware that neither of these printers can print satisfactorily on 0.4mm so
there's little point having a control. The control is literally spitting filament out the side.
Let's see how these printers cope with the larger nozzles.
Filament types. --------------
Before we get the results I want to discuss TPU filament. If you've bought multiple brands then
you probably are aware that there is a massive range of what's sold and described as 95A. 95A is
a hardness rating that's ascertained by poking a sort of thing into a block of the material
and figuring out the displacement, so either it's not a good measurement of how filament is, or
more likely most of these filaments have never been hardness tested or rated at all. I couldn't
tell you what true 95A feels like but it might be one of these, I guess. I don't know if it comes
across on screen how much stiffer some of these are than others. And I want to point out that
Noulei is stiffer than the rest by quite a margin. Noulei filament is easily the most bowden friendly
TPU I have come across, which isn't necessarily an endorsement of it as a material, but more that it
is the least likely to fail under pressure, and it can typically print faster than the others,
basically due to it being stiffer. Of course, it's stiffer printed too, that's the downside.
Results --------
On the noulei blue TPU and the 0.6 nozzle the results were night and day better on the
mini delta. I was printing at PLA speeds quite happily, I even took the time to make some feet
for the printer since I've been balancing it on random objects ever since its original
sticky blob things fell off. This might make it less noisy too, silent drivers this aint!
This is why I recommend the noulei filament, being able to print at speeds like 30mm/s on a 0.6mm
nozzle with decent results - for this printer - makes printing TPU a breeze, this is undoubtedly a
game changer. And while my fast draft settings may look a bit meh in places on pikachu here, this is
due to the settings, if you used more conservative settings you would get better results.
So this looks really promising for 0.6mm nozzles.
Unfortunately not so much for 0.8mm nozzles, and the experiment did take a dark turn from here.
First I tried the blue filament on the 0.8 nozzle machine, and to my surprise the results
did not improve, in fact on the contrary. To be fair, the pressure situation was not a problem,
the extruder never failed even at high print speed, but the output was...unsatisfactory.
I tried different filaments and the results just weren't getting any better.
This finish, if you wanted it intentionally it would be fun, but I don't. What happened?
Well. This is where the experiment diverges. I couldn't understand what was happening so
went back to the 0.6 printer and tried the other filaments. I was sure to print slower,
around 10mm/s or under, to be on the safe side. Confusingly none of the other filaments would
perform nearly as well as the one reel of blue noulei.
And a temperature tower of the green noulei was...well, horrible.
It took me a long time to work out what's going on here because it's not what you'd expect.
Believe it or not, this is not a problem with the machine or the nozzle size, it's a problem
with established facts. We'll come back to this, because the next thing I did, was assume that if
my green noulei was printing like this, and making popping sounds when it printed too,
then it must be wet. Established internet knowledge says that if your filament pops
and looks like this then it's wet. Never mind that I'd only just opened it, noulei must be at fault,
supplying wet filament, how dare they? Into the dryer with you for 12 hours.
[12 hours later] And it didn't work at all.
Because it wasn't wet. It's never moisture. It's kind of a running joke I have in my head
with filament. It's never moisture.
Next I put the same filament onto the ender 3 v2 and chose
my best TPU setting and...well...this came out.
I'll cut a long story short by just explaining
without the series of boat bits and head scratching.
It turns out that TPU has a speed limit. No, not an upper speed limit. Of course
it has one of those, too much speed is too much pressure is chewed up in the extruder.
No, it has a LOWER speed limit. If you print TPU at very low speeds, well, let me demonstrate.
Do you see what it's doing under the macro lens? Exactly. It's kind
of....dripping. The pressure, believe it or not, is too low!
Of course this is going to be worse with larger nozzle sizes.
I told you it was not what you expected.
I never did manage to find a balance between pressure,
speed and print quality for a 0.8mm nozzle so I can't recommend it, but I did for 0.6mm.
So let's talk time. But first lets talk math..s
geometry and why 0.6 is bigger than you think ============================================
0.4 to 0.6mm is a difference of what, 50%? Right? Wrong.
Did you ever see 10 inch pizzas sold for £6.99, and 12 inch for £8.99?
Well, thanks to...basic maths, you should always go for the 12 inch and here's why.
The cross sectional area of a cylinder, which a pizza is..a really short cylinder,
is pi r squared obviously. We all know that. Well, we do now anyway.
So a 10 inch pizza has 5 squared times pi (remember radius is half of diameter...they dont
sell pizzas by the radius annoyingly). 78.5 square inches of pizza. Sounds like a lot doesn't it.
And a 12 inch pizza has 6 squared times pi which is 113 square inches which is
44% more! Nearly half again for £2 more? Yes please.
Anyway there is a point to this,
the same applies to nozzles. The conversion from 0.4 to 0.6 increases the cross sectional
area from 0.126mm^2 to 0.283mm^2 which is...yeah that's more than double isn't it.
And this is why the pressure is lowered so much when you switch up to 0.6mm, and
this is why the real benefit here, is the time you save. So yes - let's talk time.
let's talk time ===============
Now yes, I know some of these results are scruffy, the prep for this video took a lot
of twists and turns and I didn't want to repeat timing experiments and waste material, and in
some cases just whatever, draft mode. Focus on the time, the rest will fall into place. Honest.
So, A 0.4mm 3 wall benchy on my standard settings with
0.2 layer height takes around three and a half hours.
Whereas the very same settings on a 0.6 nozzle but with a 0.4 layer height takes only 1 hour 8 mins.
And on a 0.8mm nozzle, with 0.6 layer height, 43 minutes.
If you go more conservative with the layer heights,
you could say, 0.4noz / 0.2h = 3h22m
0.6noz / 0.3h = 1h31m 0.8noz / 0.4h = 1h03m
So you can see that when you look at time savings, you're printing the same model in less than half
the time even with more conservative settings. There are massive time savings to be made.
The BMG extruder ===============
I had this thing kicking around and in a moment of anger I decided to fit is to one of the mini delta
machines. Surprisingly it actually fit, though configuration was more involved than I'd have
liked, for one it ran backwards and also it's geared around 3:1 compared to the old one,
both of which can be fixed in config, but I also had weird buzzing of the stepper which I solved
by just retracting slower, I suspect this is due to the 3 times larger step size but this video
is long enough without looking into that. I will probably do a vid just on this extruder maybe, but
it is way more resilient when it comes to soft TPU, and I was able to print even the softest
on this printer which I hadn't before. I even swapped back to a 0.4 nozzle and
the extruder still handled it really well, so it definitely is better than stock for TPU at least,
if you can overcome the technical aspects. Oh and also when you're putting it together,
the gear goes on like this - not the other way round. I made that mistake
and it chewed up the plastic gear a bit, no massive harm done but a heads up I guess.
The Ender 3 ===========
Having learned a lot on the mini delta end of the experiment, I then took this and applied
it to my two ender 3 printers. Essentially there's no difference between the 3 and the
3v2 from the perspective of TPU printing, but I did also fit a 0.6mm nozzle on my v2.
Results were exactly as expected. The ender printers take a lot of flak for
being low end but they really do perform. I will let the output speak for itself.
And by the end of the prep for the video, this TPU had arrived, so I had to try to print it
out with a 0.6 nozzle. It looks fantastic considering it printed in literally one hour.
It's controversial but in my profiles for these prints, I have the outer wall speed
FASTER than the infill and in some cases faster than inner wall.
My theory is that I want to be able to get shiny outer walls,
while allowing pressure to level out a bit during the infill, which can print a bit slower.
It seems to work, so for the time being this is what I recommend doing. This seems like a cheat
code to me, it's the exact opposite of defaults. As you can see it certainly seems to work.
settings used for TPU ====================
I'm going to show you my settings now, pause and copy them, but also I'm sharing
them on the website, link below in the description. These settings work on the
ender 3 and v2 on any bed texture because TPU is very tolerant to just about any surface.
The settings also give me good results with ALL my filaments and I've tested it out on
both ender 3 models with glass and textured bed. The settings work well out of the box for all
three colours of the noulei filaments that I tried in the video, and also for the blue ziro filament.
If you find yourself looking for these filaments after watching this video then links are in the
description for each, and you can apparently support the channel if you buy through them,
although I just set this up so who knows if it will work.
And of course if you want to perfect your prints even more
by fine tuning the retract settings and temperature, go check out my other TPU video,
link in the description or the card I already showed you at the beginning.
Tidy up and conclusions =======================
Don't switch off yet, this is the most important bit, I want to tie everything
up into some fairly neat advice based on everything I found during the video.
first layer slow irregardless ============================
you're "squishing" which adds extra pressure, newton's second law,
the bed is pushing back at you, so don't push your luck on layer one.
It typically doesn't matter if layer one looks awful so it's absolutely a good idea to put your
first layer down at 10mm/s or less. I tend to do a 50% thicker first layer at half normal speed,
this doesn't make it thicker because cura will compensate by lifting the head further,
but what it does is gives you more filament to work with so less chance of poor adhesion.
don't obsess over strings ========================
I'm going to show you a trick that most of us know already but I think few people
actually do in reality because it requires you to have a heat source. This is a butane torch,
be careful with these, they are pretty gnarly, but I'm using this as opposed to a lighter because
quicker, directional and no soot. Just turn it on and wave it over the piece and strings disappear,
and ok, bigger ones turn into warts. But yeah that's a cool trick for dealing with those
messy hairy bits that you always seem to find in your food an hour later, never understood that.
Summary =================
OK so this is important, to kind of find some semblance of advice to give you out of all this.
Firstly a 0.6mm nozzle is actually a really good way to print TPU on a bowden, you get faster and
more reliable prints, it's a game changer. You of course sacrifice some resolution but remember
you can still print lower line heights so really the loss of resolution is largely
restricted to the tops and bottoms of things. So would I recommend a 0.6mm nozzle for TPU?
Yes, especially if you either print mostly TPU or you have a dedicated machine for it.
Secondly, don't waste your time with 0.8 or bigger. At no point did I get
satisfactory results. You might, but I guarantee it's not worth the sacrifice.
Thirdly we learned that for good results when printing TPU you need the outermost wall to
be printed at between around 15 and 30mm/s, this is what makes it smooth and shiny. Lower
than this will give poor or inconsistent results, depending on the brand I guess.
Fourthly and finally you can increase the range of filaments you are able to print with
if you upgrade to a BMG style extruder, although I, perhaps irrationally, don't think I'd want to
do this on my main machine. I am happy to have one machine with this extruder on, but I just prefer
the stock extruder on the ender, and calibrating e-steps was a hassle. While it is a game changer
of sorts, I would only recommend this on a dedicated TPU machine, but it's up to you.
So this is the end of another video that proves that you absolutely don't need a direct drive
printer to print TPU. And with that, I'm off to check out ender 3 direct drive upgrades.
For science.
As usual let me know what you think in the comments.
I'll tell you what I think - I think this has given me a headache. But, what a result.
Thank you for watching!