Printing with TPU, any tips?

Larger models apparently become flow rate limited for the material. I'm surprised this model is considered "larger". My alternatives are to reduce MVS until it works, which increases print time, or find a TPU material with a higher MVS. Most filament suppliers don't tell you this number. But I think it is possible to calculate it based on nozzle size and layer thickness. On the hunt for a better flowing TPU, it seems there are some newer versions on the market. Whether their MVS is really higher, well I will have to calculate it, or measure it. But it is worthwhile to find a better MVS as it translates to faster print times.

@brino I have had to play with temperature. It seems TPU doesn't care about enclosures, or that is what I have read. Don't have an enclosure yet, I need to print parts and haven't gotten a round tuit.

As for a trusted supplier, who knows if any of them really are trusted. I tried Amazon Overture TPU, that's the green stuff in the picture, and Sainsmart TPU. I reverted to the Overture, because I had successfully printed with it before, although not with as large of a model. The Sainsmart allegedly has a higher MVS. (May have used too high of a tension for the Sainsmart.) But maybe it isn't an MVS problem. 3d printers seem to have a whole lot of knobs to tweak, and it's not apparent to me which one's to try or avoid.
 
https://muppetlabs.co/3dprinting_techniques_calibrating_volumetric_rate.html gives a way to determine MVS experimentally. I may try it tomorrow to see if I can verify my current settings, on the filaments that I have. I should be receiving some GT-3 TPU from Sainsmart that allegedly has a higher MVS. They claim higher print speeds. That wouldn't be bad. But what I really need is simply a reliable print in under a day.
 
Made it past the point of the last fail. At 43.6mm, out of 180mm so far. At 10mm height/hour, this sure takes a long time...
MVS = 3.5, as loose a tension I feel comfortable with, 10mm retraction and de-retraction. I'll know better in the morning.
 
Not encouraging to wake up to the sounds of clicks, the clicks of extruder jam.:confused:

Drat. Made it only 42%, or 118mm of 180mm. Failed in a region of large internal fill, similar to the last time, but further up. Well, that's the end of this experiment. Need to do something a bit different, because this just isn't working. I've practically lost track here, but think I'm at 0 for 7 at this point. Plan A isn't working.

Think I'll do some extrusion testing, maybe there's some insight to be gained. Is this Plan B?

This material really seems to have a mind of its own. Fails after nearly 12 hours of printing, but looks ok before... Was tough to clear the jam, there were multiple folds of filament in the extruder. Need a plan C, A is dead, B is just info.
 
I have the same luck with TPU. With my Voron anyway.

The the Flashforge does good with it. The Voron, even with the same settings, not so much.
 
Sometimes the blind squirrel gets the nut. Success! Using the better Sainsmart material (since it had higher MVS than the Overture) and lowered MVS to throttle the speeds, the darn part finally - after the 9th try, the part printed after 19 hours. It's kind of a stringy mess internally, but I hope I can at least see if my original crazy idea works at all. Will be a separate project to make a nozzle for my hot air gun to blow air deep into the part to clean up some of the stringing.

Basically had to slow everything down, way down. And had to loosen the tension on the extruder a lot. I thought the screws were going to fall out sort of loose. But that is what TPU seems to need. Little parts print fine, the bigger ones get into volumetric flow issues in a hurry and require a lot of throttling.
 
I knew your persistence would get you there!

Thanks for sharing what you've learned.

Brian
 
brino said:
I knew your persistence would get you there!

Thanks for sharing what you've learned.

Brian
Click to expand...
I'm redesigning stuff to avoid this again. Make it more modular and in smaller pieces, rather than being monolithic.

It was not good to find failed prints after so much time into the print. Even if this part works I don't think I'll try to print it again. Too hard to get it right - basically not enough margin in the printing process. May have been luck that 9th time. Or I got the combo right that day.

It's interesting to me though that the filament profile doesn't work as is on bigger parts, but does on smaller ones. This material needs a lot of tweaking and at the moment, I don't want to make printing itself be my hobby. I want it to just work and assist my creative process. So there's a love hate relationship with this 3d printing. When things are working it's great, when you can't print something after many tries, well, it really tests your resolve.
 
WobblyHand said:
After a while of ok but not great TPU printing, I started having problems. Still too much stringing. Have knocked down the temperature quite a bit and things are a little better. Occasionally the TPU would jam in the extruder and then would print nothing. This seemed to get worse over time. Recently I was 0 for 5 in printing a larger object. Smaller objects would print fine, but larger ones didn't. The failures didn't happen right away, they would happen 10 hours into a 12 hour print, which was quite frustrating.

It seems I had the tension too tight among other things. So I backed it off.
Other things that I had to fix.
  • Reduce the retraction speed by over 1/2.
  • Reduce the print temperature to 218C. The default settings were too hot for this filament.
  • Disable Input Shaper
  • Slightly reduce max volumetric speed
Click to expand...
Have you tried filament and zhop retraction (distance inputs)? I believe those were some suggestions with my stringing PETG.
 
WobblyHand said:
I'm finding it very difficult to print a larger model in TPU. Small one's are relatively easy. I had to back off the tension a LOT. When there is no filament, the springs need to be loose (untensioned). Currently 0 for 6 in printing a large model. Been quite frustrating to print hours and hours then have a filament jam spoiling the print. Seems an extruder jam is unrecoverable, unlike running out of filament (if you had a sensor).

About to throw in the towel on this, been at it for a couple weeks with little to show.
Last flop went until 37.4mm out of 180 mm. Jammed during the internal infill. Best one got to 111mm out of 180mm. This latest try is a 20 hour print. If it doesn't work this time I need to try something completely different, probably a total redesign and smaller in size.
Click to expand...
Your close enough to me. Want me to try it on my Bambu Labs P1S (would need your filament roll, wife not happy with the stack I have now)?
 
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