this one simple trick can save your tpu
oh HI, I was er..
In this episode I show you what I did to this cube and what it means for TPU printing especially
with softer TPU like 85A or less.
Let's go.
This video is sponsored by PCBWay, more on that later
So I was asked by one of our discord members to test 70A TPU on the creality ender 3 S1
plus here because it uses the sprite extruder, not the pro one, just the basic one, because
I have previously praised this extruder excessively for its "normal" TPU performance, it's one
of the best extruders out there for TPU in my opinion.
The problem was, I couldn't get a good result.
I tried the usual stuff, slowing down to around 10mm/s, didn't work, was getting these marks
all over it, like underextrusion.
Even increasing the flow to 140% wasn't helping and this is what I'd normally do.
But then I noticed something.
Here's the thing.
With the tension up to absolutely full on the extruder, so that's with absolute maximum
grip which is an insane amount, watch.
That's going to take some explaining so let me try.
If we look at the tensioner ...which means having to take it apart, ugh..........
[Epic ragtime theme ensues]
If we look at it though, what it does is increase the tension significantly between these two
gears.
But, and this is a big butt, hehe, the distance between the teeth can only go so small, because
you're not going to get enough tension to overcome science - the teeth will fully mesh
here and that will be the most you can dig into the filament.
On PLA that would be way too much tension, but as I keep saying, TPU isn't like PLA,
and apparently it doesn't see any good reason why it needs to follow the rules.
Even at full tension it's not well held.
This is going to be an issue with any extruder with dual gears for exactly the same reasons.
A single gear extruder with a flat opposing surface might work better, and that's kind
of hilarious, another example of the engineering challenges involved in printing with TPU.
In the last video I spoke about loosening the extruder for TPU, so if you watched that
you're probably wondering why I'm now recommending tightening it.
Well - I'm not.
Because everything in that video is still the case, we have the stuff going on after
the extruder, and we have now discovered there's more stuff going on behind the extruder than
we previously realised.
And so the fix is to remove that variable.
To remove what's going on behind the extruder.
How I did it was to pull loose enough TPU off the reel to remove the resistance and
that's the easiest solution, but of course longer term if you want to solve this then
you might consider bearings on the filament reel or maybe a special low friction reel
for TPU, and definitely bypassing the filament sensor.
So in case you still don't know what I'm talking about, the force required to pull the filament
off the reel was too high for the amount of grip the extruder could realistically maintain,
it could mostly do it, but any slippage would cause underextrusion, and when it tries to
pull, it stretches, which makes it thinner, and more likely to slip.
Does this affect ordinary 95A TPU too?
I would say it's likely, but the extent will depend on the setup and most of the time,
probably not noticeably.
But I have had printers with very high friction filament sensors to I would say sometimes
yes, even 95A will be affected.
I guess we should test it to be sure, I have some ideas.. let's do that, after the message
from our sponsor.
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this video.
Here's the results.
Also what I'm saying here is entirely irrelevant for subtitles.
How about this instead: 🐇. Don't compare machines because the cubes have
been sliced differently, so for example the 3g on the ender s1 plus is probably higher
infill or something, I didn't really think about that when slicing because I didn't know
we were heading for a spreadsheet.
In a way, this is good news, because it shows that the phenomenon I discovered wasn't particularly
repeatable with lower elasticity filaments, you can see a bit of falloff if you really
add friction to the line of some of the filaments by either moving the spool away from the direct
path which is what the extra friction was, or adding the reverse bowden which was about
40cm or so of tube.
The point is, I think, that 95A filament really isn't appearing to be susceptible to pre-extruder
tension as I wouldnt expect it to be, just like PLA, I don't think this is a huge factor,
the extruder can pull over a kilogram of force sometimes much more as we saw in the last
episode so it's only seeming to be an issue in the higher elasticity more slippery filaments
like the 40D and way moreso with the 70A.
I did mention that I didn't expect to get on to spreadsheets from a simple observation
about underextrusion, so there's probably a lot more you could do here, this is still
a relatively uncontrolled experiment which I would say contains one strong learning outcome,
and that would be to be careful with tension on very soft filaments.
So there you go, what do you think, I personally think it's hilarious, TPU is always full of
surprises, and the idea that a single gear extruder works better just flies in the face
of established knowledge, but I should say that part is still a working hypothesis - I
may test it at some point.
Anyway that is all for now, remember to subscribe for more 3d printing stuff and I will see
you later!