[Solved] Prusa Mini: Filament frequently jams after about 2 hours of printing  

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

That's a good suggestion, but I don't have any good reference points to do that.

Still, I did take measurements with my MK3S which has been working fine with these filaments. There, the multimeter still read a bit low, but not as low as the Mini, albeit still roughly in the same neighborhood.

I chatted with Prusa support and they suggested reading the resistance of the two thermistors. The hot end thermistor read 101.5 kΩ, while the heatbed thermistor read 115 kΩ. Both were at room temperature and read the same on the LCD, so it's certainly possible that my hot end thermistor may be out of spec.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Posted by: @marc-c13

That's a good suggestion, but I don't have any good reference points to do that.

Still, I did take measurements with my MK3S which has been working fine with these filaments. There, the multimeter still read a bit low, but not as low as the Mini, albeit still roughly in the same neighborhood.

I chatted with Prusa support and they suggested reading the resistance of the two thermistors. The hot end thermistor read 101.5 kΩ, while the heatbed thermistor read 115 kΩ. Both were at room temperature and read the same on the LCD, so it's certainly possible that my hot end thermistor may be out of spec.

Put the thermistor of your multimeter in the middle of a pan with boiling water. Not at the bottom of your pan. It should be around 100-110 degrees c. 

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I also tested now printing PLA with around 230 C and quality improved significantly even with the Prusa GAlaxy Silver PLA. I'm not sure what is causing the issue but during my 14 hours print quality changed and after that it has been much harder to work with the same filaments.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I think that looks like underextrusion, but I have to admit that the pattern looks kind of cool. 😀 

A couple of thoughts:

1. You might try performing a cold pull to see whether it cleans out anything that might be stuck inside the hot end. There may be a bit of debris in there causing the underextrusion.
2. You might also try 240° to see whether that behaves any better. In my case, I'm now printing the first layer at 235° and subsequent layers at 230°, but at 240°, things were working well albeit with a bit more stringing (which has been reduced since lowering the temperature).

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Yes the pattern is actually nice, hats why I kept it 🙂

I'm new to 3D printing and just learned what does the cold pull means. Thanks for the tip. Maybe the debris from the old filament are isolating the heat a bit and thats why adding some 10-15 degrees improves the quality.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

We have found that our brand new filament from Prusa could not print and constantly jammed in the head. We could calibrate the first layer, we could get a partial printing of the first layer of the NUT sample, but it always had issues with extrusion rate, and then when it jumped to the second layer the print would adjust the head temp down a few degrees and the extruder and head would jam. To clear the jam the bowden would need to be removed at the head and then feed some clean filament through, trim it, reattach the bowden and purge. After doing this many times we really got it jammed up and had to completely remove the bowden, the extruder and dug into the filament and mangled it, then it pushed that into the bowden where it got good and stuck. 

After trying a number of things and going back to the little sample filament from the printer and still having issues I was about to box it up and have Prusa pick it up. We kept at it and increased the head temps to 235 and suddenly it worked great! 

I have no doubt our mini is not reading the correct print head temps. 

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Posted by: @wayne

We have found that our brand new filament from Prusa could not print and constantly jammed in the head. We could calibrate the first layer, we could get a partial printing of the first layer of the NUT sample, but it always had issues with extrusion rate, and then when it jumped to the second layer the print would adjust the head temp down a few degrees and the extruder and head would jam. To clear the jam the bowden would need to be removed at the head and then feed some clean filament through, trim it, reattach the bowden and purge. After doing this many times we really got it jammed up and had to completely remove the bowden, the extruder and dug into the filament and mangled it, then it pushed that into the bowden where it got good and stuck. 

After trying a number of things and going back to the little sample filament from the printer and still having issues I was about to box it up and have Prusa pick it up. We kept at it and increased the head temps to 235 and suddenly it worked great! 

I have no doubt our mini is not reading the correct print head temps. 

Most likely, you have some plastic under the PTFE that is causing your problems.

Peter

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

I too have found that printing at 10 to 20c higher than normal seems to keep things moving.

I had perfect results for the first 2 weeks of everything I gave it. I was astounded at it.

Then I had three things happen in very short succession:

1. a failed unload procedure (I think this was caused by the too low temp in the hotend)

2. I then canceled a failed print on the first layer and the head crashed on the x axis ( I had to do a full reset and calibration to get it working)

3. Then the filament (esun pla+ and prusa) has been repeatedly getting blocked. 

Since then I haven't had a 100% successful print. 

Raising the temp and slowing the print 50% is helping but it seems crazy after my first 2 weeks of perfection 🙁

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

After reading more reports here I decided to adjust the hotend up higher (then adjust the bed sensor higher also). This was very easy and has fully cured our Mini. We went from a brand new printer that could not get past the first layer to a perfect printer. I am now VERY pleased. There are many discussions about adjusting the hotend, I think even a video. Check them out, it is very easy and should get you going again. We now have zero issues and each print is so much better than our other printers.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@wayne

ive got a farm of bowdon printers that are NOT as finicky as the mini.  Ive had multiple filaments that I generally run at 195 jam at 215 in the mini (all hatchbox colors, zyltech, and a few other PLAs that people wont recognize)

im not sure I want to run them at 235 - as that will make details less effective...

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@benjamin-g11, I'm suggesting that 235° really might not be 235° as one gets on a different printer. It's possible that the thermistor values in the firmware may not be quite right, or otherwise some of us have either slightly faulty or out-of-spec thermistors.

Prusa did suggest that I repeat my testing after upgrading to the next firmware. I did a print a piece using 3D Solutech filament at a more typical 215°, and it seemed to print fine. I'm going to need to do more tests to see whether the firmware actually made any difference, though.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@marc-c13

so um.. that firmware update seems to have done the trick... wow.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

Zdravím,

Měl jsem podobný problém, vytisknul jsem několik modelů z přiložené flash. Potom jsem použil jiný plast než "Prusament" a došlo k ucpání trasy filamentu. Filament jsem odstranil a potom byly další výtisky špatné. První vrstva v pořádku, ale druhé a následné vrstvy se trhaly, nepřilnuly a byly celkově špatné. Částečně pomohlo zvýšení teploty PLA na 230 °C a zpomalení pohybu extruderu. Nakonec jsem vyzkoušel postup "g-j-sieben" (nejsem si ale jistý jestli jsem ho správně pochopil), a zvedl jsem jsem hotend - posun o několik "mm" směrem do větráčku.
Zkontroloval jsem trubičky aby na se lícovaly a představte si, ono to jede?
Nyní budu testovat. Vůbec si nedokážu vysvětlit k čemu došlo a jak může rozdělání a složení pomoci i když už tisknu 4 roky a mám nějaké zkušenosti?
Vypadá to, že postup "g-j-sieben" funguje.
Ukázka nepovedeného tisku.

Martin E. L.

Hello,

I had a similar problem, I printed several models from the attached flash.
Then I used a different plastic than "Prusament" and the filament route was blocked.
I removed the filament and then the other prints were bad. The first layer was fine, but the second and subsequent layers tore, not sticking
and they were generally bad. Increasing the temperature of the PLA to 230 ° C and slowing down the extruder movement helped in part.
Finally, I tried the "g-j-sieben" procedure (but I'm not sure I understood it correctly), and picked up the hotend - moving a few "mm" towards the fan.
I checked the tubes to make sure they fit, and imagine it going?
Now I will test. I cannot explain what happened and how can education and composition help even if I have been printing for 4 years
and have some experience?
It looks like the "g-j-sieben" procedure works.
Sample failed printing.

Martin E. L.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

 So, I too was unable to print with any filament other than the Prusament samples that came with my Prusa Mini. I implemented the procedures as outlined in the YouTube video by @brad-w2, and I was able to successfully print the JP whistle with three different filament other than Prusament. Referring to the attached photo, and from left to right I used Prusament, Proto-Pasta, SnoLabs, and a eight dollar special from Amazon that no one wanted to claim, as there wasn't a brand name on the box or spool. 

At least in my case the video was helpful and effective. I have sliced a few files and will attempt to print them and see how it goes. I will post my results, good or bad 

.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

After slicing and printing several files including the rocket (thing:2008193) which is printed in double wall vase mode, I believe I can safely say, at least in my case the fore mentioned fix has solved the issue. Also, there was no post processing on any of the files in the photo. The Prusa Mini print quality is very good. 

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@treyrey64

... which is printed in double wall vase mode ... How is that done?

I only know the vase mode with single wall in PrusaSlicer.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

My friend got his Mini recently and was having underextrusion issues after successful Prusa-tuned Benchy prints, failed prints after a couple hours, having to use higher temps than his MK3, etc. The filament wouldn't retract, he'd have to remove the internal PTFE tube to cut off the mushroom. The screws on the side for holding the hot end were pre-torqued so tight the heads were already rounding out, so he couldn't get them out to adjust the height as noted in this thread.

I'm still waiting for my Mini, and was panicking after hearing his issues so we had a closer look together. We found that the PTFE tube was not squarely cut, it was angled and crimped like the assembler had used side-cutters instead. It's no wonder there was a mushroom on the filament. We cut a fresh tube perfectly squared off, left it a tad long at ~1.5mm above the body before we put the fitting back in so it would have a little bit of compression.  Calibrations were successful and the test print was great!

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@treyrey64

Those are some really nice results indeed. Thanks for sharing.

@rgustafson

I am not sure why but after all these issues seen in the forum Prusa needs to upgrade his quality control.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@area51

Sorry, double wall vase mode is a misnomer. The rocket was printed in single vase mode. I just set up the slicer to print with the wall thickness doubled. ie. .8 instead of .4. It greatly strengthens the walls of printed model. BTW, it works even better when printing with PETG over PLA.

We just got into the habit of calling it "double vase mode" within my group of friends.

RE: Prusa Mini: Filament frequently jams after about 2 hours of printing

@rgustafson

PTFE tubes are cut by a machine they made themselves. But there could be some bad piece, even machines have bad days. Person assembling it should have spotted it though and throw it away.