Having trouble when printing with PolyFlex™ TPU

[Naamakasa 0]

Hello

 

I usually print with PLA tough or normal PLA and use PVA as support material. Now I decided to try flexible material, so I chose Polymakers PolyFlex.

 

So my problem is that after 10 minutes of printing the print stops and error message is that "material appears to be empty". And when I release the motor the filament is highly tensed in the bowden tube. So it's supplying more of the filament that is actually coming out of the nozzle. And when the tension is high enough the motor is not able to push more filament in, so it thinks the material is empty.

Also the part walls dont seem to connect and they are seperated from eachother. I'm using Ultimaker S5, the default settings for TPU material, AA 0.4 extruder and the filament is brand new from the vacuum bag.

I've tried to adjust couple of settings: layer height, printing temp, material flow %, printing speed and retraction.

I think the problem is that the filament motor is so far away from the extruder so it gets tangled in the bowden tube or something.

 

So the question is that: Is it even possible to print TPU with Ultimaker S5 and what am I doing wrong?

[gr5 2,167]

Yes it's possible.

 

You chose one of the hardest materials to print on a bowden printer.  It's the left most material on my graph here:

http://gr5.org/mat/

 

I recommend you try something like cheetah which is a little stiffer but good enough to make things like sneakers.

 

Anyway, to print this material you need to do a few things. 

1) Set the feeder to the lowest tension (and don't forget to put it back when you switch back to "normal" filaments). 

2) Print at 1/4 the speed you were printing before.  All 7 or so printing speeds (like infill).  Not just the "main speed".

3) Add oil to the filament.  People just seem to refuse to do this but it works!  It works very well.  The friction in the bowden is quite high without adding oil.  I add one drop per meter.  This filament is so flexible (like string) that you can put the printer to the rear of a table and move the table away from any walls by a bit and unspool until the filament almost touches the floor.  Add one drop of any kind of light petroleum oil (baby oil, 3-in-1 oil, sewing machine oil, not cooking oil which will go rancid).  Add one drop every hour or so - or better: every meter.  You unspool another meter and add one drop at the same time.  People think the oil will end up affecting the print - making holes or something but it doesn't.  It works very well.

4) Maybe raise the temperature a little bit.  Look up recommended print temp range and print probably at the high end. 

5) If steam is coming out or you hear sizzling (water boiling) then you also need to dry your filament.  Unlike PLA you need to keep TPU very dry.

6) Regarding retraction - you want just enough to relieve the pressure in the bowden without actually pulling out of the feeder.

7) Flow - you can increase flow a bit but do not go over 5% extra (105%).

 

If you still see gaps in the walls - go to the TUNE menu and play with the speed (slow it down some more) or raise the temp.  Keep notes about what you did.  If you can't get rid of the gaps you failed.  You have to get rid of those.  They tell you that you have underextrusion.  Did you add the oil?  No?  Well then that's the problem.

 

If you get Cheetah or similar stiffer filament you don't need to do any of this.

 

 

[TimonR 21]

On top of the changes mentioned by @gr5, for TPU the problem is also that the processing temperature window is very narrow. Luckily the Ultimaker TPU or Generic TPU base profile is already optimized for TPU printing. However, the printing temperature is very specific for each TPU.

So if your print temperature is too low, you underextrude/grind/get an error. If your print temperature is too high, you get degraded (matt) material and eventually an error as well, as the degraded material builds up in your nozzle.

Typically printing at the lower range of the specified temperatures at low speed gives you reliable results, as with a Ultimaker / Bowden printer it is especially hard to print fast with TPU.

If you want to have a hassle-free experience, try Ultimaker's own TPU, then we basically did all this optimization for you (though you have to make sure the material is dry if you're not using a Material Station) 😉.