The solution to this TPU problem was surprisingly simple!

super helpful, thank so much for sharing this

I believe that i just stumbled onto the solution for a problem that I unknowingly ran into just today. I'll strip tpu off the spool and retry my print to see if the problem goes away. Thank you!

Thank you for sharing your great observations that substantially increase the community knowledge on TPU printing. I sell a product that I 3D print from TPU 98 and I'm developing a TPU 95 version. I pull a foot of TPU filament off the reel when I start a new print to prevent the extruder from stretching the filament that could cause a slight under extrusion on the critical initial layers and have the extrusion variable set to compensate for filament stretch but that's difficult to adjust because the moving print head unreels filament when at the edge of the part's print envelope (under extruding during this process) and then prints from the slack filament the rest of the time.

I recently upgraded to an Elegoo Neptune 4 Pro and I'm still experimenting and learning about TPU on this new extruder. Your observations were very useful in helping me understand what's happening although I think I had a good intuitive understanding of the problematic TPU extrusion based on a few years of manufacturing experience. I'll definitely try extruder pull out tests on a couple of durometers of TPU, and I'll weigh some test cubes with TPU printed off the reel versus TPU with slack filament above the extruder.

I'd previously considered building a TPU detensioner that is essentially a driven gear and sensor just below the filament run out sensor that pulls the TPU off the reel to keep constant slack in the TPU as it feeds into the extruder. It may be time to revisit that project for printing softer TPU filaments.

I long ago switched to hanging the reels a couple of feet above the printers and feeding the filament directly down into the extruder. That's the only way I could get TPU to print. I can't believe people try to feed TPU through a reverse Bowden tube. I didn't even consider 3D printers with a reverse Bowden tube such as the Anycubic Kobra 2 because I print a lot of TPU.

such a complex explanation which doesn't make sense

I am now printing decent 95A TPU filament with ball bearing filament holder, ball bearing filament feeder, 30 mm/s outer layer, 3mm/s retraction, 10mm/s first layer, 220 C extruder 60 C bed my cheap/trusty good ol' Ender 3! Thank you for the knowledge 🧠

I just wanted to thank you for your TPU videos They've helped me time everything in and my TPU printing game is strong now. Nice and smooth and super glossy. TPU ROCKS!!!!!!

found out the same thing. When using flexible filament you need to manually loosen the filament off the roll. Larger rolls have higher resistance than smaller rolls. I get great results by doing this. A pain, but necessary.

I did 75a with a ender 3 neo max and got a wolverine cowl at 102% in 11 days .04 nozzle I couldn't di 95a it kept messing up. Just a Capricorn.

do the single gear dd extruder video! do the single gear dd extruder video!

guys buy a bambu lol

Put sunrise extruder and all you're problems will fade

Do you think the bowden hotends print TPU better than all metal hotends? my all metal direct drive setup is having issues with friction in the hotend but a sprite bowden setup might fix that

do I get cactus as a present with my order to PcbWay?

I have noticed on my direct drive extruder when printing with 95A TPU a brand new 1kg roll has slight under extrusion defects that self corrects as the roll is used up.

the subtitles not matching the actual video content is incredibly annoying

This video is AMAZING! Thanks for making it - at first sight it wouldn’t deserve such a lengthy one, but I truly enjoyed the journey 😊

I have had the same results needing to reduce resistance to get it to print using a single gear extruder. The dual gear extruder have worked better, but I have yet to test other flexible TPU materials. I have a longer LLK5 PRO for the single gear extruder, and a Sovol 4 3d printer with dual gear direct drive.

I have same issue. I use 3mm id bowden tube to feed filament to my direct drive extruder on my diy core XY. Decided to try TPU for the first time after printing exclusively PETG for 2 years and my TPU first try failed because of friction in bowden tube. now i have to design new spool holder to feed filament without restriction

"Also what I'm saying here is entirely irrelevant for subtitles. How about this instead: 🐇." Hahaha welcome to the Matrix, man!

Wow finally someone that has my exact problem! It's been months of stress and tests and i finally came to this video. The point on the sprite extruder of the s1 is that even at full tightness it doesn't grip well TPU 85A or less. I upgraded to a full metal heatbreak and i use a smooth spool holder (bypassing the filament sensor obviously) but it seems like i can't go faster than 20 mm/s and i can't push retraction over 2 mm, wich is absurd. Even with theese settings my prints are far from great. Do you suggest replacing one of the extruder gears? What is the real solution to this? Is the sprite extruder bad at printing TPU and i can't do anything about it? That would be actually funny since i bought the S1 to print TPU. If you have an answer to this please tell me 'cause i'm out of hope right now.

I thought when I saw the video start.... I wonder if he rolls it off the spool!
I spent days trying to work this out on my Orbiter2 extruders using Overture TPU - on Cardboard spools. I kept getting what I thought were clogs on 2 different printers. Only by pure accident I noticed excess filament I rolled off printing just fine, then as soon as it went taught and had to pull on the spool it had under extrusion again.

Thank you.

he might have different definitions of simple in mind 😂

I have an old Fablicator FM1 that has a smooth bearing roller that swaps out when using TPU for this very reason. That printer has always excelled with TPU (even NinjaFlex)

My Prusa's - I had to loosen the tension on the bondtech double gears, also switching to a .6mm nozzle did wonders. Prints flawless.

this is exactly the results I had. I printed 95a with no issues at all.. but determined my part needed softer filament... so I movedd to 85a and started getting under extrusion. Trial and error showed that if I pulled the filament out and bypassed the filament sensor I could get good prints. Even after switching to a spool holder that had bearings, it was still a problem. The mass of the spool was enough to cause the under extrusion. Problem is that with a 12 hour print I needed to just sit there and pull out filament.. not going to happen.

I am still searching for a solution, going to try a small reallly light spool on the bearing holder next.

OH! PULL THE FILAMENT OFF THE SPOOL.

That makes sense. Especially as I dried my Filamentum 98A in a dessicator and the filament seems to want to stick to itself and takes more effort to pull off the reel.

THANKS SOLVED ON SPRITE PRO NEW SUB

I would hope that you do test it (that single gear actually is better than dual gear with tpu) at some point, because you spent 2 videos ive seen inferring it.

If i want to bypass the filament sensor you can just put a piece of filament in there so its always giving off a blue light

I tried printing an object using Ninjaflex 85A, and got the same results you did, after successfully printing a temp tower and retraction tower. Good info and thanks! Special note, I had just taken it out of my filament dryer, probably didn't help the situation.

Brilliant! Thank you.
I print a fair amount of TPU. The easiest are Ninjatek Cheetah and Overture High Speed. For softer applications Polyflex 90A works well but I have to print much slower.
After seeing this video I am looking forward to retrying the softer materials I have struggled with in the past.
Thanks.

I've been meaning to build a better spool holder, I currently have my spools in a dry box next to the printer, it's on rollers and rolls fine but the filament needs to travel through the filament detector and across the frame and that's really not ideal. When I was printing TPU I just let the spool on its side on the desk next to my printer, it basically unspooled itself without any issue. It doesn't work with PLA or PETG but I don't have issue with those, at least the issues aren't as severe. I did print a hanging filament spool holder with bearing but there's very little friction, it turns out you want a little friction because the whole spool basically ran out.

Concave feeder gears are the best imo. better grip overall

PRUSA MK3s with SaintSmart TPU. Loosening one turn the tensioner seems to work. Also bypassing the MMU2 is imperative. Fil rol on top of the extruder with the standard PRUSA trays that came with the MMU2 and have ball bearings. Slack is not necessary except when loading

Does anyone know gow to print tpu on entina2 printer

Love your tpu videos! you've covered the bowden worst-case, would you be interested in covering the 'new printer' worst case? Something like tpu with all metal hotend and oddly designed direct drive gearing?

Im very glad i watched this. Just printing tpu 1st time on my new ender3 s1 plus. No issues yet but i didnt actually know about that tension screw, so if i do get an issue i know what im checking.

You always need to adjust your tension depending on the material you use. With PLA / PETG it´s just not noticeble at all you will be usually fine but as you can see here TPU is a different story.
Also the dual gear extruder in general is not a great solution since one of the two gears will be always out of "sync" you will always get surface inconsistency with this style of mechanism.
The forces in our 3D Printers are usually very small, so for most applications a direct drive single gear extrudder with a PTFE boden tube (non all metal hotend) will be the best technical solution for PLA / PETG / TPU especially TPU though.

maybe an even more overkill solution is to have an extra stepper motor to pre pull the filament so there's a perpetual slack

Hey! Thank you for the very detailed information exept for one: Which filament did you use exactly?! Link would be much appreciated ;)

Off topic, how to you like the screw driver? I was concerned it would not have enough torque... you seem to use it with no issues. Recommend?

Bondtech lgx ff. G10 build plate. Tpu perfection....

Took me a few days to watch this, but very interesting. I have the regular S1 and I have super soft Ninja Flex, which doesn't print nicely, but I'll try this next time. Why bypass the runout sensor?

Great explanation thank you. I was about to buy a dual gear extruder for TPU without ever testing my current ender extruder which i've converted to DD using all original hardware.

Give us the NEPTUNE 3 PRO review pleeaseee
im waiting with my finger on the trigger

I love your videos, man. Entertaining and educational. Cheers

I think I'll have to try the tug test with my Bondtech dual gears. I believe the spacing of the two hobbed channels is significantly closer on those than what you depict here. I've not had issues with TPU as low as 82A yet.

Is there any way of trying a dual motor extruder, one being the main extruder motor (situated at the extruder like a normal direct drive) and the other one just pulling filament from the roll (situated near the filament roll like a bowden one) mimicking the main extruder movement, so the tension generated by the extruder from pulling the filament is removed. In short, a printer with two motors for the extrusion system, one normal direct drive extruder and the another motor as a bowden extruder that work with exactly the same movements.

Have been printing a bunch with 85A TPU on my Ender S1 without problems.