Extrusion failure / clogged nozzle since Upgrade to MK2.5
 

Extrusion failure / clogged nozzle since Upgrade to MK2.5  

Page 1 / 3
  RSS
lena.b
(@lena-b)
Active Member

Hi together,
I get strange nozzle clogs mid-print since I upgraded to MK2.5. I already tried a few things, such as

* Cold-Pull
* I have a dust filter
* Retraction set to <0.8mm
* Nozzle height adjusted
* Different print temperatures (so far: 205°C to 220°C)
* Printing way slower (30mm instead of 60mm)
* Changing filament types (different qualities of PLA, although I did not have problems with all of them beforehand, which means a day before)

Still, nozzle keeps clogging. It never happens immediately. Sometimes it comes after a few ten minutes, sometimes only after 2 hours or so. It goes down to extruding nothing at all at times, and not extruding anything until the end of the print - and sometimes it's "just" skipping a few motor steps, or a few layers.

What I did then is sit right beside the printer until I hear the first extruder motor skips and tell it to "change filament". See the attached photo (sorry, not the best picture) for what I pulled out yesterday. Remember, I did this immediately mid-print, so the nozzle did *not* have time to cool down at all. I wonder how it comes I can see the nozzle imprint, since normally the PLA melts and I don't pull something that well-defined. This is more or less equivalent to what I pull when I cold-pull. Pulling that out, though, did require much less force than a "normal" cold-pull.

So I asked myself how this can come, and my only conclusion so far is: "something is wrong with the hotend, and most probably it's not heating correctly". Maybe some loose connection? But the octoprint interface did not show a "significant" temperature drop (see second picture). I mean, I see a temp drop, but it's not *that* far, still well above 200°C. So I guess both the temperature sensor as well as the heater "should" be working correctly? I did not have a look at the printer's display for the temperature in that moment.

Do you have any ideas for
a) what can be wrong
b) how to fix it and
c) how I can debug further - preferably without spending my free time sitting right next to the printer for hours?

Cheers,
Lena

PS: maybe it's nothing, but when I have a very close look at the octoprint screen shot, right before the mini-spike downwards in temperature, for some reason the temperature curve is very flat, with much less noise. You can't really see anything than the target temp curve. Can this mean it does not get a reading at all?

Posted : 02/08/2018 8:10 am
christoph.h5
(@christoph-h5)
Eminent Member

I currently have a similar issue but still struggle to completely solve it. I have been through your list of counter measures as well, without success.
I had this problem on a MK2/S, which I then upgraded to the MK2.5. As I suspected the extruder and or the feeding mechanism to be the problem, I hoped that those would go away. This was not the case, although with the upgrade, all parts were exchanged (extruder, change to bondtech gears etc.).
I have tried loosening and also tightening the screws on the idler with little luck…
I will try printing a new spool holder with as little friction as possible as it seems to me that it could be caused by too much friction to unroll the spool. Maybe the current heat wave also is not helpful, if it is related to heated up bondtech gears.

Currently, I am printing only small things (with a maximum of about 3 hours printing time), so the failure rate has gone down to about 20%.
However, what I have also noticed is that if I print objects with a lot of retractions, the failure happens earlier so it seems to be related to retraction. I am currently playing around with this but managed to print successfully an object with a lot of retraction, by completely switching retraction off. A lot of stringing was occurring but proved my assumption. I am still trying to find the sweet spot (trade of between retraction, failed print and stringing).

Posted : 02/08/2018 3:32 pm
lena.b
(@lena-b)
Active Member

Yes, I had a similar idea that retraction might be the root cause somehow - although I was using settings around 0.8mm now, and beforehand (on the MK2S) I did not have problems with 2mm. And the hotend stays the very same. It worked a little better without retraction, but it did not go away for me.

However, my failure rate currently is somewhere around 90% :-/. Before I upgraded to MK2.5, it was more around 5%.

Posted : 02/08/2018 10:20 pm
christoph.h5
(@christoph-h5)
Eminent Member

I am currently doing some testing (in the evening) with retraction, so here are my current results:
The model I am using: https://www.thingiverse.com/thing:275091 (the part I am printing is TRex_Ribs_Left.stl (with lots of retractions).

Here are my results (all with standard retraction speed of 35 mm/sec):

  • two prints with 0.8 mm retraction length: not successful

  • two prints with 0.5 mm retraction length: not successful

  • three prints with 0.3 mm retraction length: one successful

  • one print with 0 mm retraction length: successful, lots of stringing

  • one print with 0.2 mm retraction length (and retraction speed at 25 mm/s: currently running
  • Posted : 03/08/2018 12:32 pm
    lena.b
    (@lena-b)
    Active Member

    Update:
    * While my print failure was around 90% with PLA for larger objects (>1h print time), very small objects worked okayish
    * Printing with PETG did not (!) cause any issues. I was able to print all the parts for the R3 extruder (had the R2 one beforehand).
    * I exchanged the R2 parts for R3 ones. Printer has been calibrated, and I'll try another PLA print over night. We'll see how this works out.

    I chose to try the R3 parts since they should have better cooling.

    While I disassembled the printer, I found a serious amount of molten PETG on *top* of the Heatblock. I don't know exactly how it got there, but the Heatsink was supposedly not very well attached to the Heatblock, for $reason. I heated it to 240°C and re-screwed it. We'll see if that was part of the issue.

    Cheers,
    Lena

    Posted : 05/08/2018 11:07 pm
    OPK
     opk
    (@opk)
    Trusted Member

    Hi Lena,
    My problems are the same, also after installing the R3 parts. I noticed that when it fails you can also not push the filament through by hand. I wonder could it be that the hotend has cooled down too much, but is is not registered by a faulty thermostat? Next time it fails (always PLA), I will measure the hotend temp "by hand"...

    Posted : 05/08/2018 11:36 pm
    christoph.h5
    (@christoph-h5)
    Eminent Member

    Hi Lena

    Thank you for the update. I will try printing the R3 parts as well and disassable the printer to install them. Maybe I can see a similar problem as you have seen... It will take a few days but I will update on my findings.

    Posted : 06/08/2018 9:34 am
    OPK
     opk
    (@opk)
    Trusted Member

    Hi, upon reassembly of extruder, make sure the with an open "gear door", you can push and pull the filament in till the heat block without any effort. In my prints of the R3 the tube got positioned just a bit too much to the front, resulting in some resistance when I push the filament in. I kept completing the extruder update without fixing it properly - I now regret that as my PLA prints still fail one hour in.

    Posted : 06/08/2018 2:01 pm
    lena.b
    (@lena-b)
    Active Member

    Hi together,
    I still have the same issues after updating to R3. I'll try what OPK suggested as soon as the currently running print is done (or failed :-/)!

    Cheers,
    Lena

    Posted : 08/08/2018 9:41 pm
    lena.b
    (@lena-b)
    Active Member

    Oh, additionally I can rule out the hot weather (thought it might have something to do with not enough cooling), since it is way cooler today and it still hops at least over a few extruder steps (I keep hearing it).

    Posted : 08/08/2018 9:43 pm
    lena.b
    (@lena-b)
    Active Member

    Still no luck. I am quite sure that the filament runs effortless through from top to bottom. I re#arranged the pulley about like half of a millimeter, but that did not change anything.

    I really am out of ideas :-/. Currently I regret updating to MK2.5, because I did not have any of these issues beforehand.

    Posted : 10/08/2018 4:45 pm
    jayme.c
    (@jayme-c)
    Active Member

    Having similar issues with my upgraded Mk2.5 and PETG. Currently testing settings found at: https://shop.prusa3d.com/forum/others-archive--f66/first-time-printing-with-petg-problems--t14771-s20.html Which have seemed to solve a few issues. However the big problems still remain:

    * After getting to 1.2mm -> 1.6mm, the printer calls for a change of filament. It's a single material print. This will happen 2-3 times before settling down.
    *After 45 - 60 minutes the filament stops being laid down. This acts like a clogged nozzle, but on reset, it flows normally.

    There is often a time when I'll need to manually advance the filament from above. Just pushing it down will suddenly engage the feeder pulleys.

    First layer adhesion is good 95% of the time. This issue is new as of the upgrade to the Mk2.5. Calibration and square-setup tests all show excellent or perfect results, leading me to think this is all about the extruder.

    J.

    ...
    Posted : 11/08/2018 8:46 pm
    philip.d5
    (@philip-d5)
    New Member

    I am having the same issue as many of you. Things worked great before upgrading my 2s to 2.5 but now I can't seem to get a successful print on anything over ~30min of print time. I have my printer in an enclosure so maybe heat has something to do with it as others have suggested?

    The problem on mine sounds like the extruder skipping steps, or something to that effect. It is a clicking sound. When I observe the stepper while it is clicking, I can see it jumping back so maybe retraction has something to do with it. The problem only sticks around for a little while before things return to normal but since the layer it printed while clicking is trash, everything above it is too.

    I've tried pushing the material through with steppers disabled and it seems to require an inconsistent force. I've tried a cold pull, but the cold pull showed little stuck material. I've also tried intentionally binding my spool to see if my spool holder was causing trouble, but the extruder removed the spool from the spool holder before stopping. The nozzle is clear as well with no blockage. The bontech gears are meshing and the filament is aligned between them so any misalignment has to be below.

    I haven't completely disassembled the extruder, but I guess doing that and checking alignment below is going to have to be the next step.

    I am regretting upgrading right now and I am considering downgrading back to 2s just to try and get my success rate back over 10%.

    Posted : 14/08/2018 2:30 am
    helene.i
    (@helene-i)
    Active Member

    Phillip D5

    Yes please try and print with your enclosure off. The Noctua fan is not as powerful as cheaper but noisier fans and airflow is dramatically reduced.

    I have a MK3 but for about a month now I couldn't figure out why the extruder would stop extruding any filament and it was air printing at about 60-70% of the job.

    I thought maybe my hotend heatbreak is faulty, but nope turns out that my extruder motor after about 2 hours of print (specially lots of retractions) becomes really hot, like about 80-90 degrees and the metal pulley gears were basically heating up causing the filament to soften before it even enters the hot end, causing jams at weird locations such as the heat break neck and the PTFE tube...jams were happening waaaay before it is supposed to enter the heat block section.

    The silly thing is, I have an enclosure and this is simply to keep my pets away from the printer, so i have now made windows in the enclosure so hot air would dissipate and sat a desk fan on the side to help circulation.

    after the enclosure is ventilated my jamming clogging problems stopped and printer extruder now is cool to the touch and prints are coming out better than before.

    Posted : 14/08/2018 6:58 am
    helene.i
    (@helene-i)
    Active Member

    Phillip D5

    Yes please try and print with your enclosure off. The Noctua fan is not as powerful as cheaper but noisier fans and airflow is dramatically reduced.

    I have a MK3 but for about a month now I couldn't figure out why the extruder would stop extruding any filament and it was air printing at about 60-70% of the job.

    I thought maybe my hotend heatbreak is faulty, but nope turns out that my extruder motor after about 2 hours of print (specially lots of retractions) becomes really hot, like about 80-90 degrees and the metal pulley gears were basically heating up causing the filament to soften before it even enters the hot end, causing jams at weird locations such as the heat break neck and the PTFE tube...jams were happening waaaay before it is supposed to enter the heat block section.

    The silly thing is, I have an enclosure and this is simply to keep my pets away from the printer, so i have now made windows in the enclosure so hot air would dissipate and sat a desk fan on the side to help circulation.

    after the enclosure is ventilated my jamming clogging problems stopped and printer extruder now is cool to the touch and prints are coming out better than before. I print PLA at 205 degrees, with bed temp at 60 sometimes 70 for better adhesion.

    Posted : 14/08/2018 6:59 am
    christoph.h5
    (@christoph-h5)
    Eminent Member

    I haven’t yet had time to install the R3 parts (namely the new nozzle fan), but I have been able to print without problems by using the following profile in Slic3r: https://www.facebook.com/groups/Prusai3users/files/ (I am linking to the file in the facebook group, you need to join the group to see it). I use the “MK3 Pretty PETG V2.ini” by Chris Warkocki, it also works on the MK2.5 and I haven’t had any jams ever since. I even printed the https://www.thingiverse.com/thing:275091 (TRex_Ribs_Left.stl) again and it worked flawlessly.

    Posted : 14/08/2018 9:56 am
    philip.d5
    (@philip-d5)
    New Member

    Helene,

    I tried pulling my printer out of my enclosure this evening and it worked. Thank you for helping me get my first sucessful print since upgrading! Science has to be repeatable, so I will try a few more prints to make sure that I didn't get lucky. I had a really nice enclosure too, guess I'll have to upgrade it to allow for cooling. I'll report back in a few days with any updates. Thank you again!

    Posted : 15/08/2018 2:02 am
    helene.i
    (@helene-i)
    Active Member

    Phillip 5

    I am glad it worked! I was agonising for a month and a half with a kilo of half completed prints since I got my machine, and it turned out to be a simple fix (just take the machine out of the enclosure). So yeah my cats have to play elsewhere, their bedroom has been taken over by the Prusa.

    Posted : 16/08/2018 6:44 am
    christoph.h5
    (@christoph-h5)
    Eminent Member

    Same here: I have my printer in an enclosure. When I close the door, my prints fail, but when I leave it open, the prints end successfully. I have a fan installed in the enclosure, but it seems it’s not getting down the temperature enough.

    Posted : 16/08/2018 12:15 pm
    pekka.p
    (@pekka-p)
    Active Member

    I got my MK2.5 upgrade completed recently and although everything went well, assembly and calibration etc., the first print was a failure:

    The PLA I'm using is cheap and prone to jams on all-metal hotends with lot's of retractions. Still, before the upgrade, I got a successful print with same material and gcode (I had MK2 with E3D Titan extruder).

    I checked the idler and the extruder and everything seemed to be ok, gears are aligned properly and material seems to extrude without problems when printing larger areas. So I thought that maybe the extruder motor simply doesn't have enough power to feed the filament, as I previously had a Titan that is a geared extruder and thus has more torque. I upped the e power from 550mA to 700mA and got an almost perfect print. MK2.5 on the left, MK2/Titan on the right. Sliced with KISSlicer, layer heights 0.1-0.25. Lower layer heights reduce the filament flow, which increases jams.

    Maybe a bit more power needed to get it printed fully. The problem with upping the amperage is that the motor obviously gets hotter. Not too hot yet since the gears don't deform PLA yet.

    I'll probably attach a heatsink on the motor and up the power a bit more

    ...
    Posted : 18/08/2018 11:14 am
    Page 1 / 3
    Share:

    Please Login or Register