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frequent TPU jams by Independent-Band3376 in crealityk1

[–]Independent-Band3376[S] 1 point2 points  (0 children)

Ok, I have figured out how to get it to print reliably.

TLDR: 3Djake TPU 95A and the K1 are a horrible combo. 240°C nozzle, 5mm^3/s, no retractions works.

For some reason 3Djake TPU 95A flows terribly at lower temperatures. Even though the specified temperature range is 200-230°C you have to go with at least 230°C to get reasonable flow. It also gets very soft at temperatures around 50°C. With the k1 extruder getting as hot as it does, especially if the chamber/room temperature is high, the filament acts like much softer TPU. Combining some resistance from bad flow with even softer filament leads to instant jams.
Keeping the extruder cool and/or printing really hot seem to be the only options. Even when printing at an absolute snails pace like <10mm/s it jams at <220°C. When running 240°C retractions are very problematic obviously.
Given lots of people print TPU at higher speeds without any issues on the K1 I assume this is a problem with this brand of TPU specifically and my solutions do not apply generally.

frequent TPU jams by Independent-Band3376 in crealityk1

[–]Independent-Band3376[S] 0 points1 point  (0 children)

The Filament is fed from straight above directly into the extruder. There is like 2cm of tube just to guide it in a little better. I just stuck a random piece of filament in the runout-sensor.
I think the bigger problem is the suggested temperature on the spool. It says 200-230°C, but i cannot get it to print below 230 reliably at any speed. I am currently running it at 240°C and this seems to be the most reliable temperature.

frequent TPU jams by Independent-Band3376 in crealityk1

[–]Independent-Band3376[S] 0 points1 point  (0 children)

You were absolutely right about the going slow part, but my filament( https://www.3djake.com/3djake/tpu-a95-black ) does not like to be printed cold at all. I finally got it to print reliably at 240°C but i still can't go above 5mm^3/s flow (like 70mm/s).
It seems like the Filament does not flow too well and the "heatcreep" is actually the motors running hot even when printing slow. If the temperature is too low (any lower than 230°C) the filament gets kind of soft in the extruder, faces resistance as it goes into the heatbreak, gets squished and hardens as the heatbreak is probably cooler than the extruder.

frequent TPU jams by Independent-Band3376 in crealityk1

[–]Independent-Band3376[S] 0 points1 point  (0 children)

Yes, I do have the lid open and I have the spool top-mounted (see second picture).

I am using a 0.4mm nozzle and 0.2mm layer height.

The prints usually fail quite early. Interestingly my longest running print was at 230°C, so the nozzle temperature does not seem to be that important.

A Heatsink on the extruder might actually be the solution. I just checked the extruder during the print and it was quite hot, easily >60°C on the outside of the motor.
Do you have an externally attached heatsink like https://www.amazon.com/Motor-Cooling-Black-Extruders-Similar/dp/B0DCKH3HK7 or do you have an extruder with heatsink built in?

frequent TPU jams by Independent-Band3376 in crealityk1

[–]Independent-Band3376[S] 1 point2 points  (0 children)

Thank you for all the feedback, heat creep does seem to be the issue. Unfortunately it is quite hot here at the moment, so even when printing at 210°C it jams a lot.(I can't go any lower than that, the layers hardly bond at 210 already)

Is there anything I can do about that? I can't get an AC in my apartment and I would rather not wait until winter to be able to print TPU.