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Printing with TPU  

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jordan
(@jordan)
Active Member
Printing with TPU

Hi there,

I have experience using TPU/Ninjaflex with Printrbot Printers, so I tried using similar settings to print on my Prusa i3 MK3S. This was a huge mistake as, despite the slow print speed (20), the Ninjaflex filament got all tied up inside the gears that turn down the filament, resulting in it not printing and I had to take apart and reassemble the extruder casing to cut it out.

I'm using Ultimaker Cura and didn't use the default TPU settings, instead opting for making my own settings profile for Ninjaflex filament based on notes from my previous experience with the material on other printers (also the default TPU settings didn't seem right to me). I'm guessing there are a few considerations I should keep for the Prusa model. Any tips on how to print in TPU/Ninjaflex with the i3 MK3S?

Posted : 01/07/2019 9:22 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: Printing with TPU

slow printing speed, low extruder gear tension, look at the provided flex filament setting for a starting point

Posted : 01/07/2019 9:31 pm
jordan
(@jordan)
Active Member
Topic starter answered:
RE: Printing with TPU
Posted by: david.a66

slow printing speed, low extruder gear tension, look at the provided flex filament setting for a starting point

Tips for settings? For my notes, I mainly use Temp: 220 C, All Speed: 20. Also, gear tension?

 

Posted : 01/07/2019 9:43 pm
John
 John
(@john-6)
Reputable Member
RE: Printing with TPU

Any instructions for setting the best tension?

i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]

Posted : 01/07/2019 9:47 pm
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(@)
Illustrious Member
RE: Printing with TPU

One suggestion I read quite some time ago, and from friends printing TPU, loosen the tension screw(s) until there is no spring contact (no tension), then turn the tension screws in 1/2 turn.  In other words, start with as little tension as possible. 

Posted : 01/07/2019 9:56 pm
Sembazuru
(@sembazuru)
Prominent Member
RE: Printing with TPU
Posted by: Tim

One suggestion I read quite some time ago, and from friends printing TPU, loosen the tension screw(s) until there is no spring contact (no tension), then turn the tension screws in 1/2 turn.  In other words, start with as little tension as possible. 

Question, is this tension setting done with the filament installed, or with the filament path clear?

FWIW, I haven't had much problem with my tension set about 1/2 turn looser than regular filament. I have my max speed throttled by setting a max volumetric flow of 3.61 mm^3/s for my NinjaFlex 85A (empirically found by feeding 60mm at different rates, this was about as high as I could go to keep from getting kinks right in the top of the PTFE tube under the bondtech gears with an extruder temperature of 230°C. (Lower extruder temperatures will require slower feed rate.) I'm still trying to minimize stringing though...

See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs

Posted : 02/07/2019 4:59 am
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Nikolai
(@nikolai)
Noble Member
RE: Printing with TPU

My approach is to unscrew it during print until it slips through and then slightly (like half turn) put a pressure on it, so it doesn't slip anymore. 

My Temp for Ninjaflex is 230-240C. I also set all speeds to 15mm/s. Fast speed changes is what sometimes generates back pressure. 

Don't underestimate first layer. If it's squished, you might get issues in the following layers pretty fast.

Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram

Posted : 02/07/2019 6:53 am
Chocki
(@chocki)
Prominent Member
RE: Printing with TPU

This may not help you immediately, but I built a skelestruder and use capricorn tubing and just throw whatever filament in without having to adjust any tensions or mechanical settings and don't have any problems or slipping.

All I do is adjust print speeds and temperatures. I did follow advice to turn off retractions with TPU, boy was that a mistake, retractions back on at 0.5mm, and yes I do get some stringing, but stringing is better than blobs!.

So maybe the issue is with the extruder design not being optimal for TPU.

Skelestruder has a shorter filament path to the nozzle tip plus using capricorn tubing which has a smaller inside diameter than the PRUSA supplied tubing. All this helps keep squidgy filament under control as it has less room to squish about.

 

This is a video by JLTX who designed the skelestruder and is printing Ninjaflex.

Note this is an early prototype of the skelestruder, which has now had improvements.

Normal people believe that if it ain’t broke, don’t fix it. Engineers believe that if it ain’t broke, it doesn’t have enough features yet.

Posted : 05/07/2019 7:03 pm
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(@)
Illustrious Member
RE: Printing with TPU
Posted by: Sembazuru
Posted by: Tim

One suggestion I read quite some time ago, and from friends printing TPU, loosen the tension screw(s) until there is no spring contact (no tension), then turn the tension screws in 1/2 turn.  In other words, start with as little tension as possible. 

Question, is this tension setting done with the filament installed, or with the filament path clear?

Buddy says with filament in - so ultra light tension. With the MK3S offset, one might wonder is no tension will work (I've heard a few say they can print PLA with the idler door open).

Posted : 05/07/2019 7:19 pm
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