Yeah, "atomic method" might take pretty long time. Needle method sounds good, just need to find a needle that is 0.4 mm or less of diameter.
Dismantleing is bit difficult, because there are so many screws... and it might mess up the calibrations?
thank you for tips
The only calibration is re-leveling the bed afterwards due to step 6 and you don't have to touch the 3 leveling screws either - just do it electronically.
Some hypodermic and acupuncture needles can be found smaller than .4mm. I ordered some online and they work well for this kind of thing.
It's not that hard to take it all apart:
1) Remove filament.
2) Remove 4 screws holding fan sheet metal thing - let it hang by wires.
3) Unscrew 4 very long thumb screws.
4) Remove the 2 screws holding that 3rd "rear" fan on - careful as there is a strong spring as you can see so hold it together with one hand while unscrewing with the other and alternate screws.
5) Remove the white teflon piece (inspect it by passing solid filament through it to make sure it hasn't smushed overly small.
6) Heat nozzle to 180C before next step or you will destroy the nut (solid PLA locks the threads) - rotate the nut with holes in it by inserting a small screwdriver all the way through two opposite holes. This frees the nozzle. Once it is free turn heat off again but no need to wait for it to cool.
7) Remove very skinny long headless screw before removing temp sensor or heater as these are held in by that long skinny thing.
8) Remove temp sensor and heater gently - make sure you do step 7 first!
Now you can put the nozzle in flame. Don't leave it in too long as even nozzles can melt but heat it enough to burn anything made from trees.
Consider soaking an acetone for an hour especially if you got tiny pieces of ABS in there also from your black feeder which can wear down into powder and get forever inside the nozzle causing problems.
'atomic method' I like that!
Now I have not used woodfill yet but I wonder if you heated up the nozzle to 200deg C and then tried pushing regular PLA in to the hotend, then set to cool to 90 deg C.
whilst it is cooling use an acupuncture needle or 0.3mm drill and push up through the nozzle.
I wonder if doing this you will push up the blockage and that will get caught in the melted PLA. when the PLA is removed at 80-90deg C it should pull out the offending junk.
It is worth a try, but give a few goes, as it can take 3+ attempts to clean a blocked nozzle with regular PLA so I would have thought it will take more to clean out wood fill.
Bob
I have now mismantled the nozzle as much as possible, but i wasn't able to remove nozzle from the wires nor from the heater.
Once i had removed all other parts from the nozzle, i started to clean/remove the burned wood/carbon. I used 2mm and 3mm diameter drills, drilled from the top hole (which is the bigger hole, about 3.5mm diameter)...I drilled the hole with fingers just in case that i wont damage the nozzle much. I also used "atomic method" now when the i had only the nozzle in tongs.
While trying to clean the nozzle i burned 4-5 times my fingers, but i managed to clean lots of the dried carbon. At the moment nozzle is still jammed, because i can't clean the little extruding hole...I don't have any nails that would be smaller than 0.4mm diameter.
Ultimaker2 nozzle...dismantled
Nozzle still stuck...all the black dots on platform are the burned/dried carbon from the nozzle
I've dismantled the hot-end (nozzle included) about 10 times. The only way that I was able to get the really bad clogs out was by straightening out a paper clip, heating up the nozzle to 190 C to where it just starts getting soft, and twirling the paperclip around the inside multiple times until all the clog is out. You can do this while the hot-end is hanging there on it's own, but be careful. (I used needle-nose pliers to hold the nozzle in place while using the paperclip with other)
Juha, PM me your address and I can send a few acupuncture needles for free.
If you are in a hurry you can try a guitar string or buy an epidermic needle in your local pharmacy.
I've dismantled the hot-end (nozzle included) about 10 times. The only way that I was able to get the really bad clogs out was by straightening out a paper clip, heating up the nozzle to 190 C to where it just starts getting soft, and twirling the paperclip around the inside multiple times until all the clog is out. You can do this while the hot-end is hanging there on it's own, but be careful. (I used needle-nose pliers to hold the nozzle in place while using the paperclip with other)
I know well this, but that won't help me...
I had started printing on Friday and the printer printed the object about 3-4hours (object was 49hours long printing). So when the nozzle jammed, it also burned for 48hours (whole weekend), that is why it is really hard stuck in nozzle.
And just like i have told before, heating up doesn't really work on carbon, because carbon is dry and burned wood.
I know well this, but that won't help me...
I had started printing on Friday and the printer printed the object about 3-4hours (object was 49hours long printing). So when the nozzle jammed, it also burned for 48hours (whole weekend), that is why it is really hard stuck in nozzle.
And just like i have told before, heating up doesn't really work on carbon, because carbon is dry and burned wood.
I didn't read through everything, so please excuse my comment if I'm making you repeat.
Sounds like you might need a video feed to prevent this from happening again. I would never let a print go unattended for that amount of time.
Did you complete step 7 above? That screw is holding in the temp sensor and heater. If you can't get the screw out with a hex wrench, just use vice grips on the tip of the screw.
Once that is out you can get the temp sensor and heater out. If they seem stuck just use pliers and get a good grip right where they enter the heater and gently twist and pull. You might need to do this while the heater is hot but not on. I did it while the head was at room temp. They slid out without needing pliers.
Here is that screw I was talking about - it holds the temp sensor and heater in place:
To which temperature do you need to cooll down before you can try to pull the filament out? For pla it seems 90 is good but when I do it with abs there is no way I can pull it out at 90. So for abs I heatup untill abs comes out then I cool down but when I wait till 90 I can't get it out. It is possible at higher temp but what would be the sweet spot for abs. I think removing the material last night caused me a blocked nozzle. I tried atomic a couple of times at 120 degrees but now my filament breaks at the top.
Ha I found the answer I think somewhere on the forum. Its 130 degrees for abs.
Please report back if that was the only thing you needed to change. You know, for science! 
I solved the clog... Atomic metod did not work, filament kept breaking at the top. Removed the nozzle (i have a um original). Tried first with a heath gun at 300 degrees to remove the material. Did not work. Then I torched it with my soldering burner. Could not remove enough material out of the nozzle. Then I soaked it with aceton. With a cloth i was able to remove enough abs so that I had the impression it will work again. The printer just finished a pla print. In the process I also cleaned the bodentube and the extruder. Al in al quite some work but the machine is operational again.....
This was a very helpful post, thanks! Followed the steps, cleaned my UM2, and now it works flawlessly.
Is there a trick to removing the heater, however? It's the only part I couldn't remove.
Thanks.
This was a very helpful post, thanks! Followed the steps, cleaned my UM2, and now it works flawlessly.
Is there a trick to removing the heater, however? It's the only part I couldn't remove.
Thanks.
As gr5 mentioned, you have to get that set screw out as it holds the heater and sensor in place. I had to heat the head up to around 200 and then used needle nose pliers to grip the metal part of the heater. I ended up cooling it and heating it up several times before it came loose.
As a side note, I would never feel comfortable leaving a print unattended for more than a few hours.
Some hypodermic and acupuncture needles can be found smaller than .4mm. I ordered some online and they work well for this kind of thing.
I second the acupuncture needles. They have worked for me, though you might need more than one. Use them on a heated hotend, obviously.
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If the wood has carbonized in the hot end you may have to dismantle it, and maybe soak it out, or burn it out with a flame to get it to break down. First though, have you tried using a fine point like a hypodermic needle to push up through the nozzle hole to see if that frees it up? Maybe do that to tear loose any junk, then repeat the 'atomic method' cleaning (push hot plastic in, let it cool and then pull out plastic and blockage)
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