In this video I will give you a simple and methodical way to customise your print
settings for EVERY roll of TPU. If you follow these steps you should be able to
significantly reduce stringing and failure - even on a bowden setup. Let's get going.
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intro -
Ask around for the best settings for TPU and you'll get a different answer every time.
While I think it's fairly well established what's best for PLA, or at least most of us
can get acceptable results with PLA, when you need to print TPU you'll find that opinions truly are
like backsides - everyone has one. And yes, some of them really do stink.
Now I want to get straight to the elep...octopus in the room. I have seen this model being shown
off everywhere online, usually with the caption "Wow, I got my TPU settings dialed in,
look at this, it's amazing. I'm amazing. You're not. You suck. Octopus! Woo!"
Now there's a dirty little secret with this octopus. Let's go have a look in cura.
Add the octopus. Now choose your standard PLA settings and slice
Go to the preview tab click "color scheme
at the top here" turn on "travels"
Look. There's almost no travels outside of the piece.
Compare it with this eevee that I'm using through most of this video and you'll see the difference.
So yeah the octopus will print perfect almost always, with no stringing other than maybe in
about four places where you can simply pull it off and pretend it never happened. It's a cheat
and I'm not afraid to say it. Because, a lot of us have seen this, gone out and bought TPU, used the
person's settings that they claim are the perfect settings, and got something like this, or worse.
Eevee is a particularly troublesome print because the ears are long, thin and parallel
which means the pressure is being applied and released during each layer in short bursts,
it's a real recipe for blocking the nozzle and stringing and will fail or look awful
on most suggested TPU settings I found online. Even some PLA prints will string on this model.
Here's my pile of calibration eevees from trying settings found online.
Some better than others, but none really great.
Now, I want to really make it clear that TPU is TPU, and the game here is compromise.
You are never going to get a guaranteed string free travel move outside of an object even with
a direct drive, what you are aiming for is minimal cleanup, and that means trying to
get as few strings or maybe just strings in places you can easily clip them. By the way
if you aren't sure what I mean by bowden and direct drive, it's pretty simple. A
bowden setup has the extruder pushing the filament from the other end of the tube,
whereas a direct drive is pulling it from right behind the nozzle. Thinking of it as
front wheel drive and rear wheel drive isn't a bad analogy. And if you think about TPU being very
elastic, you can imagine why pushing it from up to a foot away might cause some irregularities with
extrusion and pressure, imagine trying to thread a needle from that distance and you get the idea.
However all that said, I have no miracle cure or solution here but what I do have
is a process. Because we need to science our way out of this.
So - You need cura. If you're using another slicer then you're on your own,
I would suggest using cura for TPU simply because it has the most parameters to tweak AND the
plugin I'm about to tell you to get.
So yes as a prerequisite we need a plugin in cura. If you go to the marketplace,
check on the list - this can take a while - look for "calibration shapes". Install that.
You have to restart, and then after that you have to do this weird step where you
go to extensions -> part for calibration -> copy scripts, then restart again. Then you're done.
Before you start, you need a baseline TPU setting to use. You can use anything you've got really
for TPU but I would suggest these settings here simply because they work for me. Pause and copy
them if you need to. But if you already have a half decent TPU profile, roll with that.
I think the main thing to draw your attention that perhaps goes against the grain is keeping
the fan on full even on layer 1, TPU is not like PLA, you seem to get better results
setting each layer including the first one as fast as possible rather than leaving it slightly soft
which seems to be a cause of failure when the next layer ploughs it up and makes a mess.
So I don't think the order matters here but I did a retraction calibration tower first.
Go to the extensions menu, part for calibration, add a retract tower.
You will see the tower appear but don't print yet - if you do, you just get a shape.
You have to go to preferences, post processing, edit gcode.
Then in here you need to click add a script, choose retract tower.
If it's not on the list, go back a step and make sure you have copied the scripts and restarted.
Choose distance first, that's what I did. I chose a starting value of 1 and an increment of 2, so
this will give us five values of 1,3,5,7,9 mm of retraction distance. If you are printing at .2mm
layer height like I am then the default of offset 4 is exactly right, and so is change layer at 38.
If not, you will have to preview the model and count how many layers
before you need to change the values. Print this model out, and - for fear of
stating the obvious - note down the best setting based on stringing, don't focus on bridging here.
Next do a temperature tower, using the same process but using the temp tower object and
temp tower script. I found that the start and offset were wrong for me on this tower, I
had to use offset of 4 and change layer of 41, if you're using 2mm you will want to use the same but
do check it in the preview, it's important! Print this one out too and choose the one that
overall looks best, this time you're also looking at bridging as well as stringing.
Third, do another retract tower - but this time use speed, instead of distance. Same again,
default parameters work on 2mm layer height, I ran from 10mm/s up to 30mm/s in increments of
5. Be sure to note this down too, because it's easy to forget what you set. Again when it's
printed choose the best, although they likely all look good. You can see here that any one of these
settings is way better than you would think it could be. Stringing and bridging all look good.
It's worth mentioning that for retraction speed and distance you may need to compromise
depending on your printer and extruder. If you set the speed or distance too high,
you almost certainly will run the risk of the TPU bending in the extruder and this looks like a
blocked nozzle to the unaided eye, but on closer inspection the filament is kinked in the extruder
meaning it is just slipping on the spot. this happens for me if I push distance above around
10mm and speed above about 20mm/s. Of course it's filament dependent. My best advice
is to choose the lowest values that look good, and it's better to have a few spots of stringing than
a failed print so it can't hurt to err slightly lower especially on troublesome prints with a lot
of retractions like the ears on EEVEE.
So in the end you pretty much have your settings, you can if you want run some of the other
calibration tests from the plugin, but I found these three get you where you need to be. Here's
a before and after, for EEVEE. I think for three small calibration prints that's a good result.
I think, something I didn't really cover until this point is the weird idea that you shouldn't
use retraction with a bowden setup. I don't really know where this has come from, but if you follow
this advice then you will never be able to get good results on anything with travel moves outside
of parts. It's true that retraction settings seem to need to be dialed in very specifically on TPU
whereas PLA is a lot more forgiving, but how that turns into "do not use retraction" is
something I can't really follow. Any retraction is better than none. I think you probably already
know this but retraction isn't intended to remove any filament from the nozzle,
it's a means to quickly reduce the pressure in the nozzle, to try to cut the flow as you move,
and when used in conjunction with a fast travel move, does a decent job of cutting
off the filament between parts. The only time I can think you might not want this
is if you can't stop blockages any other way, or are using softer than the normal 95A TPU.
But if you're using specialist TPU then you should really be looking at direct drive anyway.
Well - that seems like a sensible point to wrap up - I hope that was of some use,
if you tried it comment below and let me know if it helped with your prints, if you have other
suggestions, also comment below. Thank you for watching!