Sudden fast backspin of the extruder, unable to print
Hello community!
I have a severe problem which makes my prusa mini currently useless.
The extruder starts to backspin very very fast (i needed slow motion to even see it) during the print of the top and bottom layers without any apparent reason. It spins backwards so fast that the filament doesn't have time to go with it, the extruder gear just grinds the filament. The tension on the screw is alsright, I checked that. Because of that, the layers a severely underextruded, like no filament is extruded at all.
It's not retraction, this works great.
I disassembled the hotend and cleaned it and changed the short ptfe tube, I cleaned the gears and even downgraded the firmware from 4.0.2 to 4.0.1.
It happens on all prints, even the presliced from the USB from Prusa.
Please, if you encountered the same problem and found a workaround, let me know!
Or tell me your ideas, maybe it will help me and others with the same problem.
Any suggestions are appreciated because currently the printer is useless with this fault.
RE: Sudden fast backspin of the extruder, unable to print
That's a rather unusual symptom. Retractions are normal part of print process, but this seems weird. Are you using default configuration of printer or did you make any modifications to extruder or hotend? Standard Prusa firmware?
It may be best to open chat with support, they will probably know of better ways to diagnose it, help with factory reset and firmware upgrade/downgrade. It may also be some new bug that they'll be able to report to devs.
RE: Sudden fast backspin of the extruder, unable to print
Hi!
Thank you for the fast reply.
Yes everything ist stock on my printer, as I got it just three days ago.
My first and second print, the nutand a cistom part sliced with prusaslicer, worked perfectly but after that, the problems started.
I used the normal prusa mini settings for the prusaslicer and havent changed anything.
I already had a nice conversation with the support team, but I assume they didn't really understood what I meant...
I just hope I'm not the only one and some genius figures the problem out.
I will try slicing woth cura later today and I will report the results here.
Thanks!
RE: Sudden fast backspin of the extruder, unable to print
Maybe a short video showing the problem will help finding the cause.
Have a look at my models on Printables.com 😉
RE: Sudden fast backspin of the extruder, unable to print
RE: Sudden fast backspin of the extruder, unable to print
This is the slowed down version of the video above. It shows how fast the motor is actually spinning.
Please help!!
RE: Sudden fast backspin of the extruder, unable to print
Hmm... Those clicks, "fast backspins," seem suspiciously like missed steps due to a jam of the filament in the extruder. Or even worse, the bondtech gear's can't hold onto to the filament due to the Jam and they are slipping.
I have seen some reports of jamming issues when using non-prusament filaments. I am wondering if this is related.
RE: Sudden fast backspin of the extruder, unable to print
Hi Scott!
Thanks for the link, I also read the thread and thought it could fit.
But I'm confused by why it is really spinning backwards, it doesn't make any sense. I even looked up in the gcode if there is an G1 command like E-100.00 or something like that but all numbers seem reasonable (although I'm not familiar with gcode).
I changed the ptfe tube inside the hotend and rally paid attention to keep the tube compressed.
Now i printed it with the firmware 4.0.2 , 4.0.1 and 4.0.0 and it didn't help.
I printed it with Prusament, too, but the problems stayed.
Also let's assume it would go away with the Prusament filament, would that mean that Prusa became the next Ultimaker where you can only use their own filament? I hope that will never happen....
Now I'm really clueless what it might be.
Update: I couldn't try it woth cura because I couldn't figure out the right profile for the mini.
Jan
RE: Sudden fast backspin of the extruder, unable to print
UPDATE:
So today I tried to solve the problem again and this is what I found out:
- I'm not able to print ANYTHING faster than 40mm/s, otherwise the error occurs.
- the error is highly dependable on the flowrate of the filament, which translates to operating speed
- I'M not sure, but I think a hotter hotend, therefore a softer filament is better than colder (220°C for Prusament)
I'm not sure what this means, but if it is true that the MINI basically quits at 40mm/s that's bad.
What are Your experiences? How fast can You print?
I included a picture from a speed test, where I started printing with 100% and every time the backspin occurs I lowered the speed by 10% absolute speed. The printer goes from right to left and You can see the frequency of the error decreases as the speed decreases.
Please, does somebody know what it might be? The screw needs 7h printing time with these parameters. That is way too long and every printer from china can do better.
I know, it's an newly released product, but I really thought it would perform better. Or I'm just the unlucky guy, who knows...
Jan
RE: Sudden fast backspin of the extruder, unable to print
Well it definitely prints faster than that, one thread over user from here posted results and print finished few minutes earlier compared to MK3S. It may be some small thing like badly pushed connector, or your printer may just be a dud, broken motor or electronics. Really talk to the support via chat, show them your videos and your recent results.
RE: Sudden fast backspin of the extruder, unable to print
Most likely one of two things:
Blocked nozzle - partial blockage (less likely)
Melted filament under PTFE tube - lower end of PTFE in heat break, PTFE not assembled correctly leaving a gap for melted filament to build up there (most likely).
https://manual.prusa3d.com/Guide/How+to+change+a+hotend+PTFE+tube+-+MINI/1505
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
RE: Sudden fast backspin of the extruder, unable to print
UPDATE 2.0:
First of all, thank you Peter, @crawlerin and Scott for the ideas and tips, that's what the community spirit is all about.
I disassembled the hotend again, and followed the instructions provided by Peter but I prestressed the PTFE tube more by rotating the upper fitting not 1/4, but 1/2 backwards.
I also checked all cables and wires and looked inside the electronics box and checked if all connectors are in the right place and plugged in correctly.
Lastly, I disassembled the extruder again and cleaned it.
And well, it seems like it's working again. Did the screw again and there was no backspinning whatsoever.
Of course it was just one 3 hours print and I don't understand why my actions could have solved the problem, but as for now the printer works great again.
Weird little guy.
I will keep the thread updated as far as there are any new events.
Jan
RE: Sudden fast backspin of the extruder, unable to print
You really do need to make sure there is no plastic in the heat break:
This one is no good:
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
RE: Sudden fast backspin of the extruder, unable to print
I'm struggling a bit to do that.
When I put out the ptfe tube I couldn't really see anything inside.
Well, it looked clean but the nozzle had filament left over because of prior printing so there wasn't any light shining through the tip.
And strangely, the cold pull failed everytime because the filament used (Prusament, dasFilament) PLA broke right before the nozzle. I tried it with multiple temperatures (60°C to 90°C).
Nevertheless, it works for the time and I hope it stays like this.
Jan
RE: Sudden fast backspin of the extruder, unable to print
Cold pull at 105 degrees 😉
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
RE: Sudden fast backspin of the extruder, unable to print
We had very similar issues - try adjusting the heat up to 230 or 235 and see if that cures the issue.
I think the temp readings on a lot of these are in error. Hopefully Prusa will respond to this issue and get it sorted out.
RE: Sudden fast backspin of the extruder, unable to print
Suprisingly, this worked for me the best and after approx. 50h printing, it still performs great:
https://help.prusa3d.com/article/e6tym5n457-clicking-extruder-mini
Thanks all for the help!
RE: Sudden fast backspin of the extruder, unable to print
I adjusted the hotend up and all is great now. Love this little printer!! No more temp issues, no more clicking, no more problems changing filament. It is perfect!
RE: Sudden fast backspin of the extruder, unable to print
I adjusted the hotend up and all is great now. Love this little printer!! No more temp issues, no more clicking, no more problems changing filament. It is perfect!
What do you mean by adjusted it up? You mean physically moved it up (with the 3 grub screws)?