Printing TPU tips?

[Jerry-rigged]

I read everywhere that printing TPU on a bowden tube machine is a PITA, but I had to try anyway. But, yeah, it has me about ready to take a hammer to my CR10... LOL

Tips to help my sanity? How do you guys do it?

Yes, I am leveling my bed, use the brim (10 passes) to verify...

Temps are 220 at the hot end, bed at 40.

Speed is (I think) 50mm/s.

My two biggest issues -

1- The filament stops feeding. The extruder is still spinning, but the something is just jammed in the bowden tube or hot end. I don't think it is a clog, I can reset the printer, pull and re-feed the filament, and everything seems to work.

2 - may be related, but often, half way thru, one layer will simply not stick to the previous layer, and it starts making spaghettis.

Help?

 

[jondilly1974]

I read everywhere that printing TPU on a bowden tube machine is a PITA, but I had to try anyway. But, yeah, it has me about ready to take a hammer to my CR10... LOL

Tips to help my sanity? How do you guys do it?

Yes, I am leveling my bed, use the brim (10 passes) to verify...

Temps are 220 at the hot end, bed at 40.

Speed is (I think) 50mm/s.

My two biggest issues -

1- The filament stops feeding. The extruder is still spinning, but the something is just jammed in the bowden tube or hot end. I don't think it is a clog, I can reset the printer, pull and re-feed the filament, and everything seems to work.

2 - may be related, but often, half way thru, one layer will simply not stick to the previous layer, and it starts making spaghettis.

Help?

I bet it is over extruding and kinking in the bowden tube. Have you calibrated your esteps?

 

[Jerry-rigged]

I bet it is over extruding and kinking in the bowden tube. Have you calibrated your esteps?

I did when I first got the machine, but honestly have probably dropped those settings. I need to re-measure the extruder speed.

I just restarted the print again, but bumped the nozzle temp to 240. We'll see if that helps.

 

[Camaroboy383]

What filament? Shore hardness?
Feeder assembly stock? If so it needs to be modified..

Those kinds of temps will make the print not so pretty unless the model is large and the layer has time to cool...

50mm is way way to fast that needs to be knocked back to 20-30mm...

 

[Jerry-rigged]

I do have the Capricorn tubing for the Bowden. Hot end is stock. I'll drop the feed rate to 70%, see if that helps.

Filament is NinjaFlex. Not sure the Shore. I also have some Ovation, but that one is still in the box.
Also, I did dry the TPU. Seems some think it will not absorb water, others say it will. But after my last set of failures, I put my TPU with my PLA in a dryer box (<30% humidity*). It has been there for a few months, so it should be dry.

*Normally the humidity is under 20%, but I need to recharge my dryers. Started that yesterday. Humidity in the box yesterday was high-20's.

 

[jondilly1974]

I run all my TPU in my food dehydrator when printing. I keep them in the foil ziplocks with desiccant packs too. I used to have issues with them making a popping noise when extruded and others let me know that was moisture in the filament. Doesn’t sound like that is your issue.

As @Camaroboy383 said above, 50mm/s is pretty fast for a TPU print. I’ve gotten much better results with the low and slow method. @suchtragedy also sent me his TPU profile for Cura that worked really well. I’ve never bought Ninjaflex, but from what I’ve read it is one of the most difficult to print thru a bowden. Most prefer a direct drive extruder for filaments that soft.

 

[Jerry-rigged]

Yeah, I never had popping, but decided to error on the side of caution.

I just checked Cura, my default speed is 50mm/s, but most of the important speeds (walls, first layer, last layer) are all 25 or 30. I think infill is about the only thing that will try to run at 50.

Current print is at Z +2.0mm and seems ok so far. 240f nozzle, F/R at 70%.??? If this one fails, I will try the Ovation TPU that I have on the shelf. It is still in the vacuum pack.

 

[Camaroboy383]

Ninjaflex is 85a.. its insanely limp compared to a standard 95a tpu..

You did not mention if the feeder is stock?
Huge factor here...

50mm sec. No good no matter where you have it set to do so.. ninja flex is 15-25mm sec.. especially through bowden..

 

[Jerry-rigged]

Feeder = extruder? It is mostly stock, (CR10) where it counts. I only upgraded the tube.

Edit - the Cura profile I was using was "Generic TPU 95A" I didn't know what the 95a stood for...

 

[Camaroboy383]

Feeder = extruder? It is mostly stock, (CR10) where it counts. I only upgraded the tube.

Yes, the feeder assembly, extruder is the hot end..

Ok.. bingo.. here is your issue.. you need to modify the feeder assembly... what happens is there is a gap between the housing and the hobbed gear/pulley.. because of the flexibility it will kink in this area and no longer feed.. if you print very very slow you can possibly get away with it..ninjaflex is very tough to print without modifications of the feeder..

You need to add a piece of ptfe between the feeder housing and the back side of the hobbed gear/ pulley... that piece should be cut like this <... so as it fits between the gear/ pulley without interference..

Pictures of stock plastic feeder and the aluminum ones..screwdriver pointing to the ptfe..? this small piece of ptfe butts up against the coupler leaving no filament path open..

 

[lycin8008]

I think printing flexibles on a bowden setup is a no-go. Too much hassle and it tends to be finicky. Do the upgrade to a direct extruder and you will take out so much headache. The PTFE tube going into the extruder is also a must, cause the flexibles can pop out and you'll just be sending your filament outside the extruder. Slow and steady WILL win you this race since it will bunch rather than force itself through the extruder. It is recommended to leave retract off and just do more post printing cleanup, but you can get by with lowering retract to no more than 4 mm and 25mm/sec, then increase the pot-retract-extrude to ~0.05-0.2 mm since you will be stringing (the nature of flexibles). Materials with a little TPU in it like some "silk" filaments can retain its heat when retracted, then when pushed back down (extruded), will swell in the heatbreak (pre-heat cartridge tube) rather than go down and you'll find your printer moving around in the air while the extruder motor is skipping all its steps.
Hope this helps.

 

[Camaroboy383]

I think printing flexibles on a bowden setup is a no-go. Too much hassle and it tends to be finicky. Do the upgrade to a direct extruder and you will take out so much headache. The PTFE tube going into the extruder is also a must, cause the flexibles can pop out and you'll just be sending your filament outside the extruder. Slow and steady WILL win you this race since it will bunch rather than force itself through the extruder. It is recommended to leave retract off and just do more post printing cleanup, but you can get by with lowering retract to no more than 4 mm and 25mm/sec, then increase the pot-retract-extrude to ~0.05-0.2 mm since you will be stringing (the nature of flexibles). Materials with a little TPU in it like some "silk" filaments can retain its heat when retracted, then when pushed back down (extruded), will swell in the heatbreak (pre-heat cartridge tube) rather than go down and you'll find your printer moving around in the air while the extruder motor is skipping all its steps.
Hope this helps.

Na, it's a go, just have to know how to get it done.. restricted filament path is key.. I run ninja flex all the time and have for years through bowden... I also run retractions just as high as pla and abs, both distance and speed.. (5-7mm 30mm/s ) with a typical extrusion temp of 207c- 215c depending on the model..

I will agree "some" direct drive units are easier.. I say some because even those need modifications to print flexible depending on the unit..

But bowden and flexibles is definitely a go..

 

[lycin8008]

Na, it's a go, just have to know how to get it done.. restricted filament path is key.. I run ninja flex all the time and have for years through bowden... I also run retractions just as high as pla and abs, both distance and speed.. (5-7mm 30mm/s ) with a typical extrusion temp of 207c- 215c depending on the model..

I will agree "some" direct drive units are easier.. I say some because even those need modifications to print flexible depending on the unit..

But bowden and flexibles is definitely a go...

Yeah, i'm not disagreeing with you on getting a set-up that works on bowden, I'm saying that you are starting a race with one arm tied behind your back, that's my opinion. You are at a disadvantage from the start with bowden extrusion and flexibles. For people new to the hobby and asking how to get the set up for flexibles, a direct drive extruder will take out most of the hassle. All direct drive extruders will need to have some modifications unless it is specifically designed for flexibles. If OP wants my opinion on which to get, it would be the E3D Hemera (formerly Hermes). It is a nice, compact unit with an excellent design, and can print flexibles. (and you don't have to bother with shaving a PTFE tube since the contour is built in)

Nice print by the way. Dull finish means you are printing in the low spectrum of its heat range. I like my TPU parts a bit shinier and print at 210-220.
My setup: Custom built Mendel-style printer with dual direct drive extruders feeding two E3D V6 hotends and a build volume of 310mm^3

 

[Jerry-rigged]

Well, it finished. But it might be the ugliest print I've done that didn't completely fail. LOL lots of gaps, and the bottom tried to do an infill for a couple of layers, so the bottom is actually see through. Looks under extruded pretty bad also. Lots of stringing, but I had retraction set to zero, so I don't think that could be avoided.

Yes, the feeder assembly, extruder is the hot end..

Ok.. bingo.. here is your issue.. you need to modify the feeder assembly... what happens is there is a gap between the housing and the hobbed gear/pulley.. because of the flexibility it will kink in this area and no longer feed.. if you print very very slow you can possibly get away with it..ninjaflex is very tough to print without modifications of the feeder..

You need to add a piece of ptfe between the feeder housing and the back side of the hobbed gear/ pulley... that piece should be cut like this <... so as it fits between the gear/ pulley without interference..

Pictures of stock plastic feeder and the aluminum ones..screwdriver pointing to the ptfe..? this small piece of ptfe butts up against the coupler leaving no filament path open..

View attachment 102162

View attachment 102163

That looks to be a good idea. I have seen the filament pop out the side of the extruder right there a few times.

 

[lycin8008]

Well, it finished. But it might be the ugliest print I've done that didn't completely fail. LOL lots of gaps, and the bottom tried to do an infill for a couple of layers, so the bottom is actually see through. Looks under extruded pretty bad also. Lots of stringing, but I had retraction set to zero, so I don't think that could be avoided.

That looks to be a good idea. I have seen the filament pop out the side of the extruder right there a few times.

Walls look good from the picture!
Is the extruder motor skipping while printing? seeing if there was a mechanical under extrusion, if so, you can increase the power to the motor by 1/8 turn at a time on the driver pot (if you do this, monitor extruder motor temp, 80C and below are working temps, anything higher and you risk shortening the life of the motor)
What is your top layer count? Adding one may help coverage over such a large area
Infill percentage? a higher percentage helps with bridging across when doing the initial top layers
With retraction at zero, what is your movement speed? You can up this to avoid too much of your material from coming out while stringing.
Another thing you can do is to enable movement over the printed part part only to prevent stringing over the unprinted part.
Also, make sure movements are optimized (just a good thing to have checked)

Cheers on the mostly successful TPU print!

 

[Camaroboy383]

Well, it finished. But it might be the ugliest print I've done that didn't completely fail. LOL lots of gaps, and the bottom tried to do an infill for a couple of layers, so the bottom is actually see through. Looks under extruded pretty bad also. Lots of stringing, but I had retraction set to zero, so I don't think that could be avoided.
View attachment 102200

That looks to be a good idea. I have seen the filament pop out the side of the extruder right there a few times.

Temps were way to high..as for the bottom..

.1 layer hieght use 10 bottom and 10 top 3 skin

.2 use 5 top 5 bottom same 3 skin..

This will ensure the thin section of the model is all solid. You could also leave low top bottom numbers if you 100% infill...


Do the extruder feeder mod, lower your temps back down to 210c .. 4mm- 6mm of retraction @25-30mm/s.. .08 coast.. .04 prime.. print speed 20mm/sec throughout.. 100% cooling travel 180mm/sec with initial travel of 150mm/ sec.. 99% extrusion rate through cura not the box..

don't start messing with dash pots.. it's not needed.. it's not missing steps, its skipping at the gear when it happens..

 

[Jerry-rigged]

I often change to 5 top layers, and 5 walls, but keep 3 layers at the bottom. I also thought I had set the infill to 100% for this one (thin walls, no point of infill). Thanks for the tips, I'll re-slice it soon, add the PTFE bit at the extruder motor, and try again.

Thanks, and I'll keep ya'll updated.

 

[Kmot]

I printed some tires and wheel chocks with TPU on my Ender 3 Pro. Yes it was a major headache to get it to the point of actually printing. I purchased a dedicated TPU extruder. I used Ninja something. I just wanted to know if I could do it. But the hassle is so much I probably won't be doing much TPU on it.

 

[suchtragedy]

@Camaroboy383's tips are pretty similar to my Ninjaflex settings I use on my Ender 3 Pro with EZRstruder, capricorn bowden tube, and stock hot end.

Ninjaflex is definitely my most difficult to get right TPU for sure. If its been exposed to air for a while I usually bake it on my oven for 6 hours @ 200°F to evaporate excess moisture its soaked up out of the air and afterwards the print quality improves quite a bit and the failures I sometimes had mid print usually go away.

I have Ninjateks "Cheetah" 95A TPU as well so it's a harder material than the Ninjaflex line, but I've come to really like and it can print at 80mm/s ?.

 

[Kmot]

Yep, that is what I bought. EZR Struder. Man, that plunger takes some super thumbs to push in, doesn't it!