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Repeated filament jams in extruder  

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adam.o3
(@adam-o3)
Active Member
Repeated filament jams in extruder

Bottom line - Since assembling my MK3, I have had repeated issues with filament jams, particularily the filament blobbing up at the extruder gear (see attached pic).

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I've had an ongoing issue with a new MK3. This is my second kit build, first one is still trucking along. On my first print, I had an extrude jam with a blob. I had to take apart the whole extruder to fix it. This caused a leaking extruder which I had to re-build a couple of times until someone linked me to the proper step by step instructions.

This said, the original issue still persists. Probably every 2-10 print hours, the extruder jams and fails to feed, with some build up just below the bondtech extruder gear.

I've read about this issue extensively online, and I am at the point where I can't tell if the problem is because the filament is jamming in the extruder or if it comes from heat creep through the heat break or what. I did notice (as some others have) that I didn't get a collet clip, I'm wondering if perhaps that's the issue? That said, the way the collet seems to work is tha the PFET tube can only go forward not back, so I don't see how having no clip would be an issue, but maybe it is? That is my last thing to try tonight is to print one with my other printer and see if it helps.

As of now, I'm kind of at my wit's end. I've re-built the hotend over 5 times at this point, disassembled the extruder to clear jams over a dozen times. I tried with different nozzles, different fiilaments and would probably have bought a new hot end if it weren't over a hundred dollars for something that I received (apparently) non-functional and also people reporting this issue indicated swapping hotends didnt work.

I did do a cold pull and got this out (see attached pic). The chunk on the tip seems to come from the nozzle, but I was wondering if maybe that second chunk the middle may be some buildup in the heat break that may be causing the jam?

I'm extremely frustrated with this printer and am considering asking for a refund because it is worthless to me.

Any further advice?

Posted : 30/11/2018 7:41 pm
Neal
 Neal
(@neal)
Reputable Member
Re: Repeated filament jams in extruder

The collet clip helps lock the PTFE tube in place. The collet will slip sometimes and when the printer does a retract it will lift the PTFE tube a bit and allow molten or soft filament to ooze between the tube and where it seats in the hotend. Eventually it results in a jam then in clicking then the back up at the gears because the sensor does not sense the stoppage as it was advertised to do before we purchased it. Remember the big deal that was made because it was a "mouse" optic and would detect stoppages?

Hope that helped,

Neal

Posted : 30/11/2018 7:53 pm
adam.o3
(@adam-o3)
Active Member
Topic starter answered:
Re: Repeated filament jams in extruder

Well interestingly enough, I would say 50+% of the time the sensor does detect the jam and asks to change the filament, but the issue is I have to disassemble the hotend to clear it, so even though theoretically I could keep printing because the sensor detected it, its very difficult disassembling the hotend while a print is paused (which locks the X axis in place) without also knocking the print etc... etc... etc...

So I have to cancel the print anyways.

Posted : 30/11/2018 9:16 pm
Robin
(@robin-4)
Estimable Member
Re: Repeated filament jams in extruder

Can i ask what is the hottest you hae had the hotend upto?

Posted : 01/12/2018 1:05 am
adam.o3
(@adam-o3)
Active Member
Topic starter answered:
Re: Repeated filament jams in extruder

Never printed above 215, though I'm sure I've heated it to 250 to attempt to dislodge the jam at least one of the times. Why do you ask?

Posted : 01/12/2018 6:47 pm
Robin
(@robin-4)
Estimable Member
Re: Repeated filament jams in extruder

Heating the hotend up to its highest temps could cause problems with the heatbreak creating a gap for blockages to happen.
It seems to be that any gap at the end of the heatbreak to the nozzle with time allow the fillamet to jam. guessing old stuck filament will harden and eventually block.
There seems to be some poorly (pre) assembled hotends about or there getting over heated?

Posted : 01/12/2018 9:30 pm
adam.o3
(@adam-o3)
Active Member
Topic starter answered:
Re: Repeated filament jams in extruder

So after some testing, I've started cooling the extruder motor and haven't had any jams in two prints, so I suspect the extruder is overheating causing the filament to soften and jam.

Posted : 02/12/2018 1:12 am
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