I recieved my K1C a few days ago and tried to print TPU.
The first few layers work fine but after some time the Filament gets stuck in the extruder. It looks like the extruder gears grind into the Material and the extruder is not able to push the Filament any further. When i pull out the remaining Filament out of the extruder it looks like in the picture i attached.
Hello @KilianB …! 
Welcome to the Creality Forum…! 
I haven’t printed TPU yet but researched that there different types. Some are too soft to push through the extruder so you might look at the different ones to see if they will work…
TPU is classified in different shore hardness types for example:
98A is harder than 90A with the number higher as it get harder. The softer one might have trouble printing…
Most of the ones on Amazon are 95A
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Thanks for your quick answer.
It is indeed from Amazon and 95A.
Do you have a solution how i can print this Material or di you think i just have to get some harder tpu?
Just like other filaments, TPU needs to be dry to be able to print correctly.
I would do that first and research different temps to see what will work for you.
TPU needs to be printed at quite a slower speed also… 
I’ve not printed it yet and I might learn from you what works… 
TPU especially needs to be dry, it strings all over the place otherwise. Do not print it in an enclosed printers, you’ll get heatcreep and the filament can bind up in the extruder. Remove the lid and open the door of the printer. Being a soft material it is a little like extruding wet spaghetti so keep the retraction distance to about 1mm maximum, there was a maximum number of retractions per distance setting but I can’t find it at the moment. This setting will stop your extruder grinding through the filament. I don’t know if you can adjust the K1 extruder manually, but you don’t want to grip the filament too tight. Some say bypass the bowden tube to give minimum resistance to the filament. I don’t do that. I have my V3SE setup almost exclusively for TPU, probably because it is a quite a slow and non-violent machine so lower your speeds and watch the flowrate. Find a brand you get on with and stick with it, I use Pinuotu but it is hard to find. I’ve used Overture but the flowrate was almost 80% to get a good print. Sunlu TPU I am trying out at the moment, its not bad.
It sticks to PEI like nothing else I have printed. Use gluestick as a release agent not to stick it down. I forgot once, the print took some PEI surface with it, you’d think the TPU would tear, no it is really tough stuff.
I figured it out now.
The spool says to print the tpu at 200 to 230 degrees, but to get it to feed properly i need to heat the nozzle up to 260 degrees. There is some stringing but thats not as big as a Problem.
That is rather high, but if it works thats fine. Had you printed PETG beforehand? Wondering if you had a partial clogged nozzle hence the high temperature.
Yes i have printed petg.
But i made sure the nozzle wasnt clogged. So that shouldnt be the Problem.
Agreed I have swapped between ABS and TPU without a clogging issue. Can’t think why you have to print so high.
Today i tried my first big print with tpu for about 7hrs.
I did a few test prints testing with different temperatures, speeds and retraction settings.
I need min. 250° C to get a good feed.
With this i can print with 100mm/s and with 1mm retraction with 20mm/s and 105% flow i get decent results.
Little stringing but that i can solve with a lighter.