Prusa Mini: Filament frequently jams after about 2 hours of printing
 
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Gabriel S
(@gabriel-s)
Trusted Member
Prusa Mini: Filament frequently jams after about 2 hours of printing

Hello,

I got a new Prusa Mini (see the Got My Original Prusa Mini Last Night post), and the test filaments worked great. The quality was awesome, and I uploaded by Benchy pictures, which looked very clean and good. I then switched to some generic PLA I had lying around and... well, it consistently would stop extruding after an hour or two. The filament would jam, and the filament loader would start carving away big gashes in the filament. "Unload Filament" was almost always useless in those tests, as it would spin and say "Unloading" without the filament moving. To unload the filament, I had to repeatedly unscrew the tube on the extruder part, and the end of the plastic would be visible but thicker (too thick to fit back into the tube). I'd cut this little bump with a scissors, press "unload" again, and then it would unload (still with gashes in the filament).

This happened repeatedly and was frustrating, so I bought some Hatchbox Black PLA on Amazon. And the quality of that PLA has been... terrible. Let's just say that. It has the same problem, consistently jamming in the extruder after about an hour or two of printing. The layers are much more "rippled" on the edges. The Prusament was very smooth, the Hatchbox is super textured on the sides and looks like the stereotypical 3D printed object. This was surprising considering how highly Hatchbox scores on Prusa Forums and on Amazon reviews. Despite my best efforts, I can't stop the Hatchbox or my other generic PLA from jamming after an hour or two of printing, mid print. 

I've given up and ordered some Prusament on Amazon US, but I'd really like to get my other filaments working. Anyone have any ideas? I'm really new to all of this, and it's frustrating to order new (highly-rated) Filament that has the same problem as the previous stuff. My temps are 215/210C on Extruder. I tried setting to 195C but it didn't extrude almost at all. 

Best Answer by Gabriel S:

Video by @brad-w2 explaining the fix:

 

Only thing I'd add: Set the MINDA probe just slightly above the extruder height, like in the video. Before this video was made, I set my MINDA probe too high and you can read what happened after that in the update post above.

Posted : 22/12/2019 4:53 am
Tomas T and Simon liked
jameswilddev
(@jameswilddev)
Eminent Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

So I've been using a lot of filaments from different brands and I have to agree that it seems unusually sensitive to differences between them.  The blue is Prusament, the red is Sunlu.  You can see over-extrusion on the bed-facing side (resulting in an undersized slot by half a millimetre), and under-extrusion on the bridge through the slot.  I've generally found that most filaments (Rigid Ink, Filamentive) print closer to the Prusament than the Sunlu.

In the case of the Sunlu, I can see ripples in the reflection while on the spool which indicates to me that its diameter is not terribly consistent, which would line up with the uneven extrusion.  Have you got any photos you can share?

Posted : 22/12/2019 9:01 am
Olef
 Olef
(@olef)
Honorable Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

My Mini also failed to unload. I too had to undo the brass fitting at the head, pull out the ptfe and filament. There was a bump which was preventing unload which I had to cut off, then unload would work.

A similar thing happened with the MMU2 which I solved by changing all of the ptfe tubes to 4mm OD x 2.5mm ID.

Once UPS deliver my replacement control screen & knob (not until the 30th - gah!) I may try changing the bowden ptfe to the larger ID stuff and festo's.

Posted : 22/12/2019 9:23 am
Cees liked
3Dprintedgr
(@3dprintedgr)
Estimable Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@olef

Newby here, can you share more info on what is that tube and what's the difference between that and a normal ptfe.

Original Prusa Mini + Smooth PEI
Prusa Slicer 2.2.0

Posted : 22/12/2019 9:57 am
You liked
Olef
 Olef
(@olef)
Honorable Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@geoper2

I haven't measured the Mini tube yet but judging by the jamming been seen it is probably the same stuff Prusa normally uses which is 4mm OD and 2.omm ID. The stuff I used on the MMU2S gives more room for the filament so eases drag, and will allow slight bulges to pass through.

The festo's are quick release couplings for PTFE and are much faster and easier to use than the brass fittings Prusa has put on the Mini.

Posted : 22/12/2019 10:05 am
3Dprintedgr and liked
Gabriel S
(@gabriel-s)
Trusted Member
Topic starter answered:
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

So, more experimenting, and... the Hatchbox Black PLA simply doesn't work. My generic PLA doesn't work. It just always gets stuck mid-print. Temps at 215C (when the actual spool says to use 190-210C) doesn't resolve it, and it barely melts at all at 190C. It's sad, really, and I'm really nervous at how sensitive the Mini is to any imperfect filament. Prusament included in the box has worked fine - but anything else, it seems, gets eventually stuck and a big mess. It has to be as perfect as possible, or it will just be unusable and will grind your filament like crazy. 

Hopefully, this can be resolved in firmware eventually. Hopefully.

Oh, and first layer: It's always great. The next layers up is where the problems start.

This post was modified 3 years ago by Gabriel S
Posted : 24/12/2019 4:44 am
Marc
 Marc
(@marc-4)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Adding my two cents, I noticed similar issues with other filament. After setting up my Mini last night, I tried printing the "nut" sample a few times using 3D-Fuel, but it kept underextruding and eventually jamming, requiring removal of the PTFE tube from the hot end to trim off the bulbous end so that I could then unload the filament.

I'm trying a print now using Prusament PLA, and it's working just fine so far.

Posted : 24/12/2019 3:18 pm
Gabriel S
(@gabriel-s)
Trusted Member
Topic starter answered:
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@marc-c13

Exactly! My Hatchbox (and other generic PLA) underextrudes, eventually jams (in that order), requires removal of the PTFE tube to trim off the bulbous end so I can unload. You've summed up what I was trying to say perfectly. And Prusament works fine.

Posted : 24/12/2019 3:24 pm
Snow
 Snow
(@snow)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I m having the same issue with esun filament, also worry at how sensitive the Mini is to any imperfect filament.

Posted : 24/12/2019 4:02 pm
a.steinel
(@a-steinel)
Eminent Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

same here with Geetech black.

Posted : 25/12/2019 10:14 pm
Marc
 Marc
(@marc-4)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I wonder what size inner-diameter the PTFE tube from the extruder motor to the hot end is. I would think it might be 1.85 mm since Prusa uses that in the MK3S hot end (ostensibly to ensure that the tips are suitable for reloading). Perhaps a 2 mm tube would be more forgiving.

Posted : 25/12/2019 10:42 pm
Roli liked
Crawlerin
(@crawlerin)
Prominent Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Is PTFE and heatbreak path wider than bowden tube?

Slightly offtopic, slightly related thought: speaking of imperfections in filament sizes - some interesting progress in terms of extruders would be if there was filament width sensor built in, and then system would dynamically adjust how much filament extruder motor pushes in, to keep flow rate constant. I know having tight tolerances in filament width would be ideal, but we do not live in a perfect world. And I am certain there is already patent for it somewhere (most probably Stratasys) so nevermind 😀 

Posted : 26/12/2019 9:15 pm
Gabriel S
(@gabriel-s)
Trusted Member
Topic starter answered:
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Suppose I should do a quick update.

I followed several suggestions from the Underextrusion thread. I unscrewed the feed into the extruder, followed by removing the screw attachment on top of the extruder assembly, followed by removing the PTFE tube underneath. I then unscrewed the three hex screws on the side, and pushed the assembly upwards after examining the inside with a light (clean). I then screwed the three screws back in, installed the PTFE and other parts, and moved the PINDA probe upwards (because otherwise it was lower than the extruder). 

I did have one problem though: After moving the PINDA upward, it was unfortunately too high and it failed to detect the surface during calibrating, making a significant circular dent in my build plate. I lowered PINDA, recalibrated, and then it all worked. I then tried again with my Hatchbox, and (mostly) success! Some zits on the build are visible, but Hatchbox is no Prusament. It printed to the end and made a decent enough job, and that's what matters. 🙂

Though, I wish I could replace my build plate, because of the dent...

Posted : 29/12/2019 12:33 am
Tomas T liked
Crawlerin
(@crawlerin)
Prominent Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@g-j-sieben

I am happy for you to have it working now 😀 Regarding the dent in build plate, you can use other side of it, or later on remove the PEI film (takes some effort) and apply new one.

Posted : 29/12/2019 2:09 am
Gabriel S
(@gabriel-s)
Trusted Member
Topic starter answered:
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Video by @brad-w2 explaining the fix:

 

Only thing I'd add: Set the MINDA probe just slightly above the extruder height, like in the video. Before this video was made, I set my MINDA probe too high and you can read what happened after that in the update post above.

Posted : 30/12/2019 5:23 am
Marc
 Marc
(@marc-4)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I wanted to come back to this post with an update.

I tried printing a new filament yesterday and ran into the same issues as I described previously. This filament is 3D Solutech PLA in "Natural Clear".

On a whim, I decided to really raise the extruder temperature. I set it to 240°. And, a little bit to my surprise, it worked fine. I'm printing a piece now that at 215° and 220° would jam very quickly and require removing the bowden tube to trim off the too-large tip, but at 240°, it's printing as smoothly as I typically get with my MK3S.

Increasing the temperature obviously reduces resistance to extrusion, so perhaps this is a workaround, but part of me wonders whether the thermistor is miscalibrated in the firmware and setting it to a more typical 215° isn't actually getting it hot enough to work with some PLA filaments reliably.

Posted : 26/01/2020 1:23 pm
Kurvalak and wayne liked
Marc
 Marc
(@marc-4)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

BTW, as a side comment, trying to do first layer calibration with a clear filament is a real pain in the a.... 😆 

Posted : 26/01/2020 1:24 pm
kUMters and Olef liked
Marc
 Marc
(@marc-4)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I just measured the heat block with my multimeter (which supposedly can handle a range of 0-1000°C), and, indeed, the temperature is low.

At 215°, the heat block was only registering around 185°, which certainly explains why most PLA filament I was trying to print was having trouble. At 240°, which I'm using now, it's actually running between 215°-223° (while the screen shows it cycling between 235°-243°), which also explains why it seems to be working well at that seemingly too-high temperature.

I don't know if I've got a defective thermistor, or if Prusa's calibration table in the firmware isn't quite right. Can anyone else who's having this problem measure their heat block's actual temperature to see if it matches the expected value?

Posted : 02/02/2020 5:19 pm
wayne liked
towlerg
(@towlerg)
Noble Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Suggest you calibrate your multimeter.

Posted : 02/02/2020 6:18 pm
Bart
 Bart
(@bart-5)
Active Member
RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@marc-c13

Depends on where exactly on the heater block you're measuring. 

I think you can't get as close as the thermistor of your printer to the heat source ( heater cartridge) with your multimeter.

You can take some tolerance on the thermistor of your multimeter and your printer thermistor in consideration.

And there you could have your measuring difference.  

A defective printer thermistor would probably show a bigger difference in temp. 

In short. Actual temp difference of the thermistor from your printer and you multimeter is hard to compare.

A temp difference of 30 degrees c is in this case not unlikely. 

This post was modified 3 years ago 2 times by Bart
Posted : 02/02/2020 6:23 pm
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