Ninjaflex Uneven Extrusion.

[MrTechAgent 2]

Hi,

So I have a lot of back and forth use of TPU-TPEs on my Printer for my work, overtime I think I have mastered loading Ninjaflex as fast as possible without issues but I recently ran into a strange issue while I was doing a print.

I noticed that Ninjaflex was not extruding properly and was leaving gaps after a certain point, then it would start printing properly, I have attached a picture in which you can see the missing spots a tiny dots of Ninjaflex indicating lack of feeding or improper feeding.

I did think of -

1) Temperature - I print Ninjaflex at 250C and there is bubbling but overall I never had issues with 250C but still I went to 240C which caused the same issue, then 230C which caused the bending and 225C was not cutting it either.

2) Layer Height - I had heard that 0.1LH is not recommended for Ninjaflex so I bumped it up to 0.2LH but that didn't solve the issue.

Now some things like going even slower (15mm/s "Printing speed and Infill Speed" in Cura and down to 50% PS on the interface did minimise but not eliminate the issue), cooling fans at 100% did help but not cure it.

One thing also came to mind, I had lowered the current on my Motors previously to solve some issues for fast printing so could that be causing the feeding motion to have uneven prints when printed at a very slow speed?

Last thing, this uneven printing isn't present when I print small to medium objects, this problem becomes more extreme with the increase in surface area of the object. I can't understand the relation since feeding motion remains the same regardless of the size but this is something I noticed so thought I'd mention it.

Right now as I write this, I'm printing the same model but going even slower (15PS-IFS in Cura and down to 45% in the interface and getting tremendous results. I can't seem to see any uneven feeding right now, I'll still update this post if in fact it finished the print successfully which would confirm that it was a speed related issue.

Thanks.

[MrTechAgent 2]

So after many troubleshooting hours I found the issue and it surprised me. It's related flow modulus of TPU and it's effect while pouring down from the nozzle. I noticed that when the material exited the nozzle and performed its Clockwise or Anti-Clockwise motion, it got stuck to certain portions of the nozzle tip and was stuck there, making the flowing material to gain some resistance and prevent it from passing freely. Once it gained enough mass to drop down it would continue until the cycle restarted.

I played with the "Flow Rate" and saw major improvements with little to no missing parts. I still am not convinced if this is the issue or there is a link I'm missing to this annoying property of Ninjaflex.

I'll still fine tune my settings for the best settings cause these results although good are not even good enough for Prototypes, will have to resort to Injection Moulding for TPUs.

Edited January 9, 2016 by Guest

[izzy 33]

I've just looked at my settings for both NinjaFlex and SemiFlex.

I print both at the same settings of,

Nozzle Temperature, 218'C

Bed Temperature, 30'C

Speed, 25mm/s ( I leave my speed set to 75mm/s in Cura for all parts, that way I can vary the speed for each material, and so reduce print speed to 30% on the machine)

Material Flow Rate, 145%, (some recommend higher up to 200%)

If printing with NinjaFlex I also add a drop or two of 3in1 oil to a pipe cleaner I loop around the filament just before the feeder,( un-oiled it acts as a dust remover) this reduces the friction in the Bowden tube.

[MrTechAgent 2]

I've just looked at my settings for both NinjaFlex and SemiFlex.

I print both at the same settings of,

Nozzle Temperature, 218'C

Bed Temperature, 30'C

Speed, 25mm/s ( I leave my speed set to 75mm/s in Cura for all parts, that way I can vary the speed for each material, and so reduce print speed to 30% on the machine)

Material Flow Rate, 145%, (some recommend higher up to 200%)

If printing with NinjaFlex I also add a drop or two of 3in1 oil to a pipe cleaner I loop around the filament just before the feeder,( un-oiled it acts as a dust remover) this reduces the friction in the Bowden tube.

 

Hi, thanks for the information.

I wanted to ask if you notice any bubbling while extruding? I did a little reading and from what I've gathered, my problem wasn't directly related to the settings but more towards the material itself.

TPU is absorbs a lot of water like Nylon and bubbling is caused which leads to uneven extrusion. I live in a very humid area but still it's quite odd for a material to absorb water so fast.

I wanted to know if you get bubbling or have you ever noticed bubbling?

I did bake the Filament hoping to eliminate any water content, haven't got the time to test and confirm if that's the solution to the issue yet.

Thanks.

[izzy 33]

I keep all of my filaments in sealed bags with the absorbent bags,in a large plastic box, but still do notice some bubbling in the head with nylon, the NinjaFlex was bubbling when it was too hot 220'C it bubbled, 218'C printed ok, but it could change slightly next time. I know some have posted about heating to about 30'C in an oven for an hour to remove moisture in other posts for material that are prone to water absorbe.

[MrTechAgent 2]

I keep all of my filaments in sealed bags with the absorbent bags,in a large plastic box, but still do notice some bubbling in the head with nylon, the NinjaFlex was bubbling when it was too hot 220'C it bubbled, 218'C printed ok, but it could change slightly next time. I know some have posted about  heating to about 30'C in an oven for an hour to remove moisture in other posts for material that are prone to water absorbe.

 

Thanks izzy, you have been a huge help.

[MrTechAgent 2]

Having tremendous success using Ninjaflex and the Olsson Block with a 0.6-8mm Nozzle. I noticed even the minuscule diameter increase and decreased feeder pressure played a huge role in combating the Water Absorption as it seems the Molecular Chains have an easier time flowing during the Thermal transition.

[uq6 0]

I've just looked at my settings for both NinjaFlex and SemiFlex.

I print both at the same settings of,

Nozzle Temperature, 218'C

Bed Temperature, 30'C

Speed, 25mm/s ( I leave my speed set to 75mm/s in Cura for all parts, that way I can vary the speed for each material, and so reduce print speed to 30% on the machine)

Material Flow Rate, 145%, (some recommend higher up to 200%)

 

These were extremely helpful and improved my semi flex prints a lot.  (I was printing too fast, with too little material.)

I'm still using a .1 mm layer height and .8 shell thickness.  Do these seem reasonable in your experience?

[sfeldman 1]

Having tremendous success using Ninjaflex and the Olsson Block with a 0.6-8mm Nozzle. I noticed even the minuscule diameter increase and decreased feeder pressure played a huge role in combating the Water Absorption as it seems the Molecular Chains have an easier time flowing during the Thermal transition.

That looks great! Do you mind sharing your printing profile?