Is it a problem with the extrusion gears or heat creep?
 
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Is it a problem with the extrusion gears or heat creep?  

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Corecost
(@corecost)
Member
Is it a problem with the extrusion gears or heat creep?

I'm having an issue where the filament stops feeding less than an hour into the print.  I can feel that the extruder is no longer pushing or pulling the filament at all.  This can be solved by pushing and pulling the filament to get it started again.  I noticed the point where the filament stopped has been worn very heavily by the extruder gears grinding. 

I also have an issue of very frequent clogging (plastic is curling up on the nozzle).  I've done multiple cold pulls and that has fixed this issue but it always comes back once this failure to feed occurs.  This is when I began to suspect heat creep may be the cause of the stopage for long enough for the gears to grind down the filament and stop it completely.  

I've tried several solutions with no effect:

1.  Reducing the nozzle temp to 210 degreees  (PLA)

2. Increased print speed to 110%

3. Adjusted the tension on the extruder gears -- no change seems to make it any more likely to succeed. 

4.  Multiple cold pulls and needles to clear the nozzle.

5.  Attempted to push up the hotend to prevent PTFE tube from having a gap, as was suggested in another thread

6.  Tried running the part fan immediately after first layer

 

At this point I'm considering buying either a new hot-end as I know there have been some issues with the prusa mini in this respect, or buying a better extrusion gear system that can actually push the filament, but I'm unsure as to the actual cause here.  Does this sound like heat creep, or some issue with the extruder?

Posted : 21/02/2024 2:40 am
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: Is it a problem with the extrusion gears or heat creep?

this could be a form of heat creep. 

Is your printer in an enclosure? or is the ambient temperature higher than normal? 
both of these can lead to heat creep

additionally Long retractions can cause heat creep are you using more than 3.2mm retraction?
Are there LOTS OF retractions due to intricate detail? this can also cause heat creep

Is the extruder cooling fan, working properly?

Is there an obstruction in the extruder cooling heatsink?

Have you checked that the PTFE Liner in the hot end is not distorted?
regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 21/02/2024 10:43 am
Thejiral
(@thejiral)
Noble Member
RE:

All of what Joan said. I'd suggest on top of that to test a temperature tower with your PLA. Start with the highest temperature and then go down to maybe 200°C or whatever the lower end is that is suggested for your PLA. 

Look at which temperature clogging starts (even signs for partial clogging, ie where layers appears underextruded etc), if you get clogging at all. If you identify a temperature where it cloggs, add 5 or better 10°C to that and never go below that value. Follow up with a test print with a lot of retractions and that "save" hotend temperatuer and check if you manage without clogging. 

I have found that some PLAs have a higher tendency for it others a much lower one to clogg if you print them at the lower end of the recommended temperature range and have a lot of retractions. Not going below a certain temperature, even if official recommendations are wider, has helped in those cases. 

This post was modified 2 months ago 2 times by Thejiral

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 21/02/2024 12:18 pm
Zeeman
(@zeeman)
Active Member
RE:

I have the same issue as OP.   I was printing PETG parts (using Prusament, 240 degrees)  for MK3S upgrade. I figured Mini can do it nicely, print a part for its big brother. Anyhow, maybe an hour in print filament stopped moving and extract/retract no longer worked and I also could not push or pull the filament by hand.

BTW, printed part looked crappy  probably because filament was skipping from the get go. So, I disassembled extruder and I discovered that filament is broken and jammed on one side and when i removed the bowden tube (on nozzle side) there was a ball-shaped blob at that end.

Back to extruder, after the cleanup of broken filament I was REALLY SURPRISED how little tension filament gear is placing on the filament and, even after adjusting the tension this did not change. I could push/pull filament by hand an I felt that it was skipping. But what shocked me (and explained the situation) is that there is only a single gear for filament push/pull?! Really? Prusa, are we still doing this today on prusa minis when even cheep Chinese printers have dual gears for filament? This is highly disappointing! Prusa should be using dual gears on all of the printers, including mini. After-all, this thing was not cheap.

I am using input shaper so extraction/retraction speeds are lot greater than without it. I suspect this is the main issue, it is likely that a single filament gear cannot cope with speeds of advancing retracting when input sharper is enabled. I did not have this issue without input shaper enabled.

So, what should I do to resolve this issue permanently? Bondtech extruder or something else? I do not think we can fix this with prusa extruder.

This post was modified 2 months ago by Zeeman
Posted : 25/02/2024 8:25 am
mark
 mark
(@mark-3)
Reputable Member
RE: Is it a problem with the extrusion gears or heat creep?

I have been able to tune input shaper and extruder tension for good results with PETG. It does not stop extruding. That being said, I see nothing but praise for he Bondtech extruder. Everything I read says it eliminates the issues with extruder adjustment and just works.

Regards,

Mark

Posted : 25/02/2024 1:25 pm
Zeeman
(@zeeman)
Active Member
RE: Is it a problem with the extrusion gears or heat creep?

thank you for your feedback. I think Bondtech extruder is the answer, I have another bondtech on a non-prusa printer and that extruder  works flawlessly.

I like their quality and I will be upgading prusa mini. Can you share your input shapper tweaks?

BTW, turns out that the issue I have  described is part of the problem, other issue is that MK3S upgrade kit that I received from prusa has a mini spool of PETG filament that I have used to print the parts. Well, it sure seems that this filament is total garbage, likely it was made from recycled material and print also failed on my yet another non-prusa printer that printed the same part without issue with different brand of filament. So, to prove the point I am running a test with a gamebird PETG, same settings and it works without any issues! So, crappy extruder aside, I received a really bad batch of PRUSA filament and this combined with input shaper speeds is what has put prusa mini over the edge! I will be upgrading the extruder and the heat break.

Posted : 25/02/2024 4:12 pm
mark
 mark
(@mark-3)
Reputable Member
RE: Is it a problem with the extrusion gears or heat creep?
Posted by: @zeeman

thank you for your feedback. I think Bondtech extruder is the answer, I have another bondtech on a non-prusa printer and that extruder  works flawlessly.

I like their quality and I will be upgading prusa mini. Can you share your input shapper tweaks?

BTW, turns out that the issue I have  described is part of the problem, other issue is that MK3S upgrade kit that I received from prusa has a mini spool of PETG filament that I have used to print the parts. Well, it sure seems that this filament is total garbage, likely it was made from recycled material and print also failed on my yet another non-prusa printer that printed the same part without issue with different brand of filament. So, to prove the point I am running a test with a gamebird PETG, same settings and it works without any issues! So, crappy extruder aside, I received a really bad batch of PRUSA filament and this combined with input shaper speeds is what has put prusa mini over the edge! I will be upgrading the extruder and the heat break.

From what I have read, I would not change the heatbreak. I have seen good and bad posts about every heatbreak, including the Bondtech. It changes so many characteristics that you will have a science experiment on your hands. The profiles are tweaked for the Prusa hot end and any changes means you have to change lots of things, print speeds and accelerations, temps, fan speeds, etc.

Tweaks for input shaper here:

https://forum.prusa3d.com/forum/input-shaper-mini/under-extrusion-or-gaps-at-seams-with-input-shaper-settings-and-5-x-firmware/

Regards,

Mark

Posted : 25/02/2024 5:19 pm
Zeeman
(@zeeman)
Active Member
RE: Is it a problem with the extrusion gears or heat creep?

Thank you Mark for your invaluable feedback and information on input shaper. Best Regards

 

Posted : 25/02/2024 6:34 pm
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