Can't print TPU as the extruder is clogging/jamming  

Re: Can't print TPU as the extruder is clogging/jamming

Any suggestions on how to succeed with TPU with the i3 MK3?

I have had really good success printing TPU with some slightly modified Extruder parts - unfortunately it turns out that the printed part filament path doesn't perfectly line up with the motor/bondtech gears in the current R3/B7 (and prior R2/B6) parts.

With my modified parts, the only jam or issue I had was while loading the TPU filament via the "Load Filament" option on the front panel menu (which really tries to load too fast for TPU already - it's better to manually slowly feed it in via the move E-Axis menu option).

See github here for a full discussion of this issue, and pictures demonstrating the curve in the filament path that causes issues with TPU/flexibles: https://github.com/prusa3d/Original-Prusa-i3/issues/51

I've posted my parts and further descriptions in the User Mods section of this forum: https://shop.prusa3d.com/forum/user-mods-octoprint-enclosures-nozzles--f65/fix-for-squeaky-extruders-especially-when-printing-t26746.html

Here's a direct link to the parts: https://www.myminifactory.com/object/3d-print-81846

Re: Can't print TPU as the extruder is clogging/jamming

Check the extrusion multiplier in filament settings. I can only get flex materials to print with a multiplier of 1.

Re: Can't print TPU as the extruder is clogging/jamming

Folks having problems printing flexible filaments might want to have a look at this gadget I just posted on Thingiverse: https://www.thingiverse.com/thing:3361565 It's a little tricky to install and adjust, but it's working well for me. YMMV.

Re: Can't print TPU as the extruder is clogging/jamming

On my Mk3 I was able to print TPE by removing all retraction and slowing down to 15mm/s. Once I did that I was able to print the tires for my 3DLabPrint QTrainer.

Re: Can't print TPU as the extruder is clogging/jamming

1. Release the pressure from the bondtech gears
2. Increase the nozzle temp if you encounter issues (235C is just perfect)
3. Print with constant speed 10-20mm/s (15-20 work best for me)
4. No retractions

It's very important to set constant speed for everything and verify that in the preview.

RE: Can't print TPU as the extruder is clogging/jamming

@nikolai-r

Thanks guys.

I was unable to print one single tire for plane from 3DLabPrint QTrainer unless I did the steps proposed by Nikolay.

I will experiment also with 240°C and higher speed, say 25/35. Alternativelly 235°C and no retractions. The goal will be to achieve higher speeds since printing with 15 mm/s is pretty slow :-).

RE: Can't print TPU as the extruder is clogging/jamming

@nikolai-r

Hi

how do you set a constant print speed for everything?

RE:

I know it's been a long time, but in case anyone else comes across this thread: I believe you'd just need to go through and manually set each of the "speed" values to whatever speed you'd like it to be. Then on the slicer preview view, at the bottom "view" selection, you can select "speed" to confirm that everything is extruding at the same speed. This is assuming you're using PrusaSlicer.

RE: Can't print TPU as the extruder is clogging/jamming

Not all TPU is the same.   For instance,   I have this coaster printing with sainsmart tpu(92A) using pretty much stock settings, including the Sainsmart TPU built-in profile.  I literally just change the print settings so there are zero top layers, and the infill type to honeycomb.  I've not adjusted any speeds whatsoever.  I even have a hardened steel nozzle on this printer which often times requires me to make minor temperature adjustments.

Ninjaflex behavior can vary, and I've found often times even with the idler bolt as loose as I can get it, I have to turn off the filament sensor for it to print.  Swiss_cheese helped me get this mostly dialed in, start with semiflex profile and just up the temp a bit and I mostly get ok results with it.

Idler bolt too tight, temp not high enough and filament needing drying are usually the problem.

RE:

I believe I may have found a consistent solution to the clicking & jamming issue.  The trick for me was to loosen the idler screws (the ones with the springs on them) as much as possible without it being completely loose.  It took some fiddling to find the sweet spot but eventually I got it working.

While troubleshooting you can reduce risk of getting the filament stuck in the planetary gears by watching closely while it pulls the filament into the nozzle -- if the clicking starts hit cancel immediately.  That way when it starts back up you can simply use the Unload Filament routine while gently pulling the filament upward.  Then loosen the screws a tiny bit more and repeat.

Note that I have the MMU idler so that may be a factor ... but in theory this should work with the original idler as well, because I was having this clicking and jamming issue even with the MMU idler.

(P.S.: I actually got this method by reaching out to Prusa Support using the chatbox on their website -- so hats off to them.)