Extrusion stops halfway through print  

RE: Extrusion stops halfway through print

short video showing the issue in action...

IMG_5536

RE: Extrusion stops halfway through print

I am having exactly the same problem and I have tried many of the strategies that you have and even tried supplying cool external air to the hot end fan via a 1.25 inch flexible duct with another 40 mm fan at the proximal end pushing more air into the hot end fan. Nothing to date has changed any of the problematic behavior. How are you monitoring the heat break temperatures? I have noted that after the extrusion fails, if I release the filament idler and manually push the filament that there is initial very high resistance before it "gives way" and I can manually advance the filament - my interpretation of this has been that it supports the heat creep hypothesis.  in addition to what you have done, I have noted no foreign bodies or debri in multiple cold pulls. I have disassembled and thoroughly cleaned and lubricated the planetary gears and housing. This problem is very, very frustrating. Can you update me here on anything else that you have tried and I will do the same?

RE: Extrusion stops halfway through print

If I ever find a solution, I'll post it here.  I'm "working" with Prusa support to try to resolve it, but the pace of interactions is frustratingly slow.  So far no solutions.

In response to your points:

• I did several cold pulls and used cleaning needles to ensure that the nozzle was clean.  all pulls came out perfectly clean with no debris.
• At the suggestion of Prusa, I did sit there looking at the heat break temperature during one of the failed prints - early in the print it was about 49C, then increased slowly to 61C at the time of failure.  I have no idea if this is "normal" or not.  Prusa did not provide any comment on that data point.

I have seen some mention in other posts re: the idler arm and idler retention clamp - some people have indicated problems with extrusion that was fixed by replacing those parts with freshly printed ones.  There is a chance that fits the problem - if those bits somehow get distorted/bent/warped, then maybe as the heat creeps into the extruder the filament gets *just* warm enough that the idler no longer does its job.  I suggested that idea to Prusa support but have yet to hear from them on it.  I may be able to print and replace those parts - they are small and would probably print successfully before the extruder acts up.  I would likely use ASA or ABS to maybe(?) avoid such problems in the future.

RE: Extrusion stops halfway through print

Just received some feedback from Prusa - support thinks it might be the LoveBoard, and they are sending me a replacement.  Not sure if that really fits the symptoms, but not sure I know all that board does, so we'll see.

RE: Extrusion stops halfway through print

I'm very much interested in finding out if this is the issue with mine as well. Looking forward to hearing how things go once you receive the new LoveBoard.

RE: Extrusion stops halfway through print

Thanks for the update.  I noted some comments in threads where some other 3D printer old timers expressed concern that the temp sensor cables exiting the heatblock looked prone to damage with nozzle changes and I notices that this area does flex a lot when removing the wires from the wire channel on the nextruder during removal of the heat block. On the theory that maybe there is intermittent heat sensor failure behind this, I  ordered a new sensor and (and new heater) and just completed my first successful print out of the last 13 attempts. I will print more and post further.  For now, as an experiment, I am being much more gentle with the temp probe and hot end heater wires exiting the heat block when I change nozzles. I hope that this helps.

RE: Extrusion stops halfway through print

Did your telemetry show any glitches?  PrusaConnect keeps all that info on a print-by-print basis.  Mine seems very stable, and I've recently replaced the nozzle thermistor.

RE: Extrusion stops halfway through print

Update re: LoveBoard replacement.  Swapped it out and, of course, it didn't fix the issue.  same failure.

I'll continue working with support and provide any updates here.

RE: Extrusion stops halfway through print

Posted by: @matt-nelson

If I ever find a solution, I'll post it here.  I'm "working" with Prusa support to try to resolve it, but the pace of interactions is frustratingly slow.  So far no solutions.

In response to your points:

• I did several cold pulls and used cleaning needles to ensure that the nozzle was clean.  all pulls came out perfectly clean with no debris.
• At the suggestion of Prusa, I did sit there looking at the heat break temperature during one of the failed prints - early in the print it was about 49C, then increased slowly to 61C at the time of failure.  I have no idea if this is "normal" or not.  Prusa did not provide any comment on that data point.

I have seen some mention in other posts re: the idler arm and idler retention clamp - some people have indicated problems with extrusion that was fixed by replacing those parts with freshly printed ones.  There is a chance that fits the problem - if those bits somehow get distorted/bent/warped, then maybe as the heat creeps into the extruder the filament gets *just* warm enough that the idler no longer does its job.  I suggested that idea to Prusa support but have yet to hear from them on it.  I may be able to print and replace those parts - they are small and would probably print successfully before the extruder acts up.  I would likely use ASA or ABS to maybe(?) avoid such problems in the future.

I have the very same issue and also tried several things:

• Cleaning the gear
• Cleaning the Nozzle
• Cold Pulls
• Adjusted idler tension screws in both directions and tried several positions
• Calibrated Nextruder
• Printed the idler arm and compared it to the installed one -> no difference
• bought a new Nozzle Brass and changed both the Brass Nozzle and the Nozzle to no avail.

I have no idea how to proceed.

RE: Extrusion stops halfway through print

This sounds a lot like an issue I had with one of my printers.  I have 2 Mk4s that were purchased 1 week apart, one of them started doing this.  I went through all kinds of debugging to no avail.  Fortunately, I had two of these, so I started swapping parts one at a time.  Hot end, gears, gear ring, idler, etc.   As soon as I swapped the extruder motor, the problem moved from one machine to another.  Prusa were great and sent me a new motor and the printer is working great now.

One more thing:  I could get the extruder to start up again, temporarily, by opening and closing the idler door mid-print.  I also printed a clear transparent gear cover in PETG as per the CNC Kitchen instructions, and that was helpful to visualize the gear movement, (or lack thereof)

RE: Extrusion stops halfway through print

Had a similar issue and resolved it as follows:

• Cold pulls, cleaning the nozle and extruder - no luck
• Replaced heater block and heater element - same again
• Removed V6 nozzle adapter and V6 nozzle and installed original Mk4 nozzle with heat break - improved a lot but, still ocassional stops
• Opened Mk4 original enclosure door to lower ambeint temperature while printing - seems like problem solved, no more stops.

In my case looks like V6 nozzle with adapter + high ambient temperature (inside enclosure was above 40 C) was the issue.

RE: Extrusion stops halfway through print

Posted by: @jwg

This sounds a lot like an issue I had with one of my printers.  I have 2 Mk4s that were purchased 1 week apart, one of them started doing this.  I went through all kinds of debugging to no avail.  Fortunately, I had two of these, so I started swapping parts one at a time.  Hot end, gears, gear ring, idler, etc.   As soon as I swapped the extruder motor, the problem moved from one machine to another.  Prusa were great and sent me a new motor and the printer is working great now.

One more thing:  I could get the extruder to start up again, temporarily, by opening and closing the idler door mid-print.  I also printed a clear transparent gear cover in PETG as per the CNC Kitchen instructions, and that was helpful to visualize the gear movement, (or lack thereof)

That indeed works. If the Filament stops proceeding, I can open the idler and it starts to move once again. I meanwhile exchanged the idler, but that didn't help. I'll need to contact Prusa Support I guess.

RE: Extrusion stops halfway through print

Posted by: @jwg

As soon as I swapped the extruder motor, the problem moved from one machine to another.  Prusa were great and sent me a new motor and the printer is working great now.

One more thing:  I could get the extruder to start up again, temporarily, by opening and closing the idler door mid-print.  I also printed a clear transparent gear cover in PETG as per the CNC Kitchen instructions, and that was helpful to visualize the gear movement, (or lack thereof)

Interesting - sounds like you are saying that the extruder motor/gear actually stopped turning.  I don't *think* that's my problem, based on two things:  the filament shows a distinct gouge where the extruder gear has been turning (see photo in first post), and the extruder gear gets plastic bits clogging the teeth.  All points to the gear turning but unable to extrude for some reason.

I like the idea of a clear extruder cover 😎 

RE: Extrusion stops halfway through print

Important addition:

- Purge 2 to 3 times before print starts

RE: Extrusion stops halfway through print

One of the things that Prusa had me do was to put thermal paste on tube of the extruder to prevent heat creep.  I think you may have mentioned you are still seeing the issue in prints with higher temp materials, so this may not be very helpful.

RE: Extrusion stops halfway through print

Well, great news (for me at least)… 

After another marathon session on support chat, Prusa sent me replacement parts for the idler assembly:  Idler Lever A+B, Idler Nut, and 2x Idler Swivel.  All printed out of PCCF, so heat shouldn’t be an issue in the future.  They also sent me the Y-tension blocks, also out of PCCF.  Sounds like they sent me everything that “might get hot”.

I installed all the bits and re-tried my test print (a small box for a an electronic device, using ASA) - and IT WORKED!  Granted this is only one print so far, but it’s the first successful print in like 6 weeks.

Seems like if they are making these things out of PCCF instead of PETG, they should probably provide them in the upgrade kit (like they did for the print fan duct).

Hopefully that’s the end of the story for this issue.  If I have any further problems with this, i’ll provide updates.

RE: Extrusion stops halfway through print

I believe to have my issue fixed as well. Not sure, if this is really true, but it might be, because of the higher temperatures during the last weeks. It seems as loosening the screws on the Extruder Cover just a tiny bit did the trick for me.

RE: Extrusion stops halfway through print

After reading several of the posts above, the mid-print extrusion failures were finally solved for me when I disassembled the entire print head completely, then reassembled it with great care to tighten everything only to the lowest torque that I thought appropriate. While I had everything apart, I also took the opportunity to thoroughly clean and re-lubricate everything. After that I am back to a 90% success rate even on 24 hour plus prints.  90% is much better than 0% but not reliable enough - I am working on feeding the Nextruder via a Bowden tube (with a second extruder) to see if the Nextruder becomes more reliable by decreasing the gradient of force across the filament drive gear.  I know that this will run the risk of introducing retraction problems but I believe that I have that solved.

Thanks to all who have contributed to this thread - I would not have gotten this far without the input!  All this is great fun and I have learned a ton researching this problem here and online, but I also have projects that need to be completed. I really love the engineering of the Mk4 in all other respects but this is the last Prusa machine that I will ever buy.  Based on my experience to date, I do not know how they have acquired the reputation of "workhorse" machines.

RE: Extrusion stops halfway through print

Sorry for the late reply - I missed the question earlier.  How are you accessing the logged data?  Is in Prusa Connect somewhere?  I've been keeping and eye on it manually (BTW thanks for mentioning the the heat break temp can be added to the display) but I have basically the attention span of a tsetse fly so that's not working out so well for me!