Problems with the filament feed for TPU lower than 94A
Hello,
I have tried a few times to print TPU with 92A, unfortunately the extruder does not manage to pull the filament through the PTFE tube by itself for a long time. As long as I push the filament into the filament sensor/tube by hand, it works. I have removed the PTFE tube from the quick connector as a test and tried to pull the TPU out by hand. This requires a lot of force and the TPU starts to stretch dramatically. To solve the problem, I have now constructed new clips to attach additional 1cm long PTFE tubes and otherwise feed the filament freely. The filament is fed in without the filament sensor, which all works quite well and does not disturb when installed on the last 5th extruder.
My question now is am I doing something wrong here and it would also work with the normal PTFE tubes with sensor, what is your experience here?
Here are a few pictures of my modification:
RE: Problems with the filament feed for TPU lower than 94A
I don't print with soft TPU, so just thinking out loud. But from the few posts I've read soft TPUs don't like getting pushed and pulled in tubes and the filament sensor squishes it too much that it essentially jams the softer TPU filament. The way I'd approach it is:
- hang spool of TPU above the TPU printtool
- stick random filament in the side sensor to fool the machine into thinking there's filament running through there
- unscrew blue fitting completely off of extruder
- TPU go directly from hanging spool to extruder
If there's trouble with initialy feeding into the gears you may even want to:
- open extruder side door
- manually thread TPU into the bottom hole past the extruder gear
- close side door and loosen tension as much as needed/possible
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RE: Problems with the filament feed for TPU lower than 94A
Many thanks for the quick reply,
I have now made some tests with TPU 85A and have to say that unfortunately I cannot make prints with the normal PTFE filament tubes because the TPU stretches too much and gets stuck in the feeder tubes.Using the above-mentioned modification, even a longer print with 85A TPU was no problem
RE: Problems with the filament feed for TPU lower than 94A
I've spent the last several days printing with soft tpu, like ninjaflex(85A). The filament runout sensor creates a TON of drag so I have to bypass it entirely for tpu. and I have just accepted I have to help the filament into the extruder at the end of the tube. I spent a good deal of time tuning the tension of the idler on my two MK4s and then the XL extruders for Ninjaflex, which is 85A. I tend to stick with Sainsmart, 92A, as it's mostly out of the box printing. Though with the XL I've had to lower the temp to the max printed on the spool(220) to eliminate excessive stringing. I hate printing with tpu but my wife unfortunately loves it.
RE:
Can you post your modified part on Printables? I was thinking of making something like that for TPU and TPE filaments.
I’ve notice I have to completely avoid running the filament through any PTFE tube and directly insert the filament into the tool head. I haven’t found the need to manually guide it down into the nozzle barrel. It seems to load fine. So far, I had good success with NinjaFlex TPU.
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SLam
RE: Problems with the filament feed for TPU lower than 94A
I have uploaded the modified clips to printables, here is the link
https://www.printables.com/de/model/718498-prusa-xl-kabel-clip-fur-soft-tpu-xl-soft-tpu-cable