Mk 3 No Longer Extruding
Hi all,
Whilst I think I know what the issue is, I thought it would be best to post to confirm my thinking.
After a successful print yesterday, I could hear a clunking sound coming from the extruder. At the time I thought it may have been some tension in the filament so I unwound a little more and then queued up my next print. For reference I am still using the silver PLA that came with the MK3 and I have used no other filament.
Absolutely no filament came out of the nozzle with the new print. I aborted the print and then tried to remove the filament, to no avail. As hard as I pulled it would not remove. I tried to super heat the nozzle to 260 to see if there was a blockage and had no luck. I tried an accupuncture needle up the nozzle (very difficult to line up correctly) and it went all the way in with no resistance.
I finally managed to remove the filament, but when trying lo load more, the clunking sound returns where I suspect the motors are trying to push the filament in, but a blockage prevents the plastic from entering the hot end. I opened up the cage to confirm this and I can see that the filament makes no progress inside after being fed past the rotating gears I can see indie. Therefore I suspect there is a blockage just past this point, where I cannot melt it out with the nozzle temperature and I cant force it down further.
I am thinking my next step will be to try and feed some wire through and push hard to see if I can dislodge the block. Failing this, I assume I will need to remove the hot end from the extruder and see if there is a blockage in the tube internally. If there is, can I use a needle file to clear this out or should I get a replacement tube? I don't really want to pay £11 shipping for a £0.64 component though, so I am hoping I can clear the blockage.
Is my thinking and next steps here correct, or have I totally gone in the wrong direction?
Re: Mk 3 No Longer Extruding
Possibly you have a piece of filament stuck in the lower part of the extruder.
Open the idler screws, disable the filament sensor (Settings)
Preheat the nozzle to around 220
once heated, insert the filament and push it down by hand, with force, but carefully to avoid damage.
If you still can't move it, take some pliers, hold the filament a few milimeters above the extruder (1/4 inch) and carefully push it straight down.
At this stage be careful to push down straight, otherwise it will break and you could slam into the extruder. If you push down straight it will give way and ooze out from the nozzle.
I have had a lot of issues with a carbon fiber filament and that always worked.
After you get it moving, you can do a cold pull.
(cool down nozzle to <80 °C, start heating it up and firmly pull up straight with pliers. around 90...110 the filament will come out and should take dirt with it.
No panic, and no metal in the extruder please! 🙂
Re: Mk 3 No Longer Extruding
Ok so push the filament in via the side door rather than the top?
Re: Mk 3 No Longer Extruding
Ok I tried this to the point that the plastic was starting to shear under the pliers. It just wont seem to go bast the top of the white tube as pictured
Re: Mk 3 No Longer Extruding
To follow up on this, I dismantled the hot end and extracted the ptfe tube to find a 1 mm wedge of pla blocking the throat of the tube. I poppet it out with some wire and rebuilt everything and I am printing a test bench now. I've noticed some oozing out of the nozzle during the warm up. Is this to be expected?
Re: Mk 3 No Longer Extruding
i had the same problem. I ended up removing the nozzle and pushing up from the bottom until it came out of the top of the tubing. I am now printing again after over 24 hrs of trying various things.
Re: Mk 3 No Longer Extruding
To follow up on this, I dismantled the hot end and extracted the ptfe tube to find a 1 mm wedge of pla blocking the throat of the tube. I poppet it out with some wire and rebuilt everything and I am printing a test bench now. I've noticed some oozing out of the nozzle during the warm up. Is this to be expected?
The 1 mm big wedge is probably due to the fact that the Teflon tube was incorrectly mounted. On your picture you see that the teflon tube is too high mounted. Then a cavity is formed at the other end of the teflon tube which causes problems.
When mounting the extruder it is important to press down the teflon tube down to the bottom and fix it so that it can not move upwards.
Bear MK3 with Bondtech extruder
Re: Mk 3 No Longer Extruding
Thanks for letting me know. I bought the printer assembled from Prusa, so you would hope things like this would be caught in the assembly checks.
Re: Mk 3 No Longer Extruding
To follow up on this, I dismantled the hot end and extracted the ptfe tube to find a 1 mm wedge of pla blocking the throat of the tube. I poppet it out with some wire and rebuilt everything and I am printing a test bench now. I've noticed some oozing out of the nozzle during the warm up. Is this to be expected?
So, the short answer is yes, if the nozzle is at the correct temperature with filament loaded, there will be oozing. I see it at 210 - 215 for PLA if i have filament loaded and the nozzle raised and heated but just sitting idly, like after a print ends and while i am removing the print from the sheet and have set the temperature for the next print....
But, not if the oozing is from around the nozzle where it meets the heat block, that is a different thing entirely... ( it usually happens with a failed nozzle change not done at correct temps) - you did not mention that, so I presume you are talking about a string out the nozzle opening.
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