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advice on clearing a jammed hotend

Posted by chef 
advice on clearing a jammed hotend
February 19, 2012 05:32PM
So, today I managed to jam and possibly ruin my hotend. I've read several threads about jammed hotends, but am not entirely sure how I should proceed. I'm using a hybrid groovemount hotend from Makergear (which has performed like a champ up until this), with a 0.5mm nozzle, running 3mm ABS from Ultimachine. I've torn down the extruder, and tried to feed it by hand, and even pushing the filament pretty hard by hand, it wouldn't feed. Upon removing the hotend, and pulling the insulation from the nozzle I found what looks like charred red ABS that had leaked down out of the PEEK portion of the hotend (see attached picture).

I've read a few threads about clearing a jammed hotend and figure I can probably find a way to get it out either with an acetone bath or using a drill bit/ream or some other mechanical assistance. The problem that I see is that I will still have the possibility of leakage in the future. Can I just unscrew the PEEK barrel and/or nozzle from the threaded brass fitting and reapply some teflon tape and re-assemble (after cleaned, of course)? Am I completely shafted and have to buy a new hotend? Any ideas why it would function perfectly for more than a month and then spontaneously give me the finger, I mean start leaking?

I fear that I have been running it a bit too hot (I have it set to 232 degrees C) and this is the result. I had been meaning to start reducing temps to see how low was acceptable, but just hadn't gotten to it yet. Any advice on any salvage technique would be fantastic. Telling me I'm screwed would be less fantastic but still appreciated as a resolution.
open | download - Jammed Hotend.jpg (303.8 KB)
Re: advice on clearing a jammed hotend
February 20, 2012 05:20AM
You could try running a small pin drill into the tip when its hot to try to break up the blockage but if that doesn't work you will need to take the hot end apart and clean the nozzle out from the inside. These Makergear hot ends are probably good when they work but total rebuilds when they fail. I know this isn't any help but in my design, where it uses a heater block, I can simply unscrew the nozzle and clean it.

Since its already messed up I wonder what would happen if you kept going up in temperature?
Re: advice on clearing a jammed hotend
February 25, 2012 08:24PM
0.5mm and smaller drills can be expensive and sometimes hard to find(in the states anyway). Even if you get one then what? wail away with a drill gun? I've been able to repeatedly clean my nozzle by soaking in acetone overnight and reaming the hole out with a piece of guitar string i measured at just under the nozzle diameter. By my thinking, if you remove any metal from the nozzle you've hurt it, so a drill is just senseless violence(unless it's held in a totally dialed in lathe or micro-drill).

I think you are fine you just need clear out the jam, you'll have better luck poking it out from the outlet side not the filament in side.
I ran without a filament duster for the first couple weeks and it clogged. Making sure the filament is clean going into the hotend is key.

hope that helps
Re: advice on clearing a jammed hotend
February 26, 2012 07:26AM
what i have done is heat the hot end up really hot with a lighter, then pulled out what feedstock i could, then i push in a2.5mm Allen wrench to push the feedstock thru, and then pull the allen wrench out. usually this will clear the blockage, but in some cases you will need to still pull out contamination.

you may have some nasty contamination in the end of your nozzle, so constantly heat up nozzle push in feedstock, and pull it out, the idea is to melt the contamination onto the feedstock.

last resort put something in the nozzle end

.drilling out the end will 95% of the time damage your hot end! never drill into the hot end. it will never work the same.

instead take a twist tie, and pull off the wrapping to expose the metal. the metal ends should be small enough to go into the nozzle;

Re: advice on clearing a jammed hotend
February 26, 2012 11:01AM
Thanks for the replies! It turns out I actually got the jam cleared using a combination of your suggestions. I tried going up as high as 240, which is as high as MakerGear recommends, but it didn't do anything and I was afraid I'd completely ruin it if I just kept going higher. I wound up repeatedly forcing a bit of filament through by hand and then pulling it out and clearing the remainder by pushing an inverted 1/8" drill bit through the filament end. I would do this until it jammed again, and then use a single strand of a piece of stranded speaker wire to go through the nozzle end to try to break up/move around the clog and then force it out from the other end (I did actually try to find a decent twist tie, but all of mine were really flimsy. I didn't think of guitar string, but that would have worked fantastic). It was pretty effective, and I had tons of extruder strands with little black charred bits in them, but it did take quite some time.

ocularb0b - It's funny you mention a filament duster. It was something that I had read about and wanted to put on the printer upon completion, but when I actually completed the machine I (like probably most people here) got all wound up about printing and completely forgot. Is there a design or method that you can recommend? At present I would say my best option would be to run it through a microfiber cloth sandwich, as I've got a fair few of them lying around.
Re: advice on clearing a jammed hotend
February 26, 2012 11:09PM
I found that just warming the nozzle would allow me to grab out chunks of abs with tweezers. Just like pushing in fresh filament, it tends to want to stick to itself. Then an overnight soak in acetone or MEK and it's as good as new.
Re: advice on clearing a jammed hotend
February 28, 2012 12:49PM
For filament duster, I had some spare pieces of assorted foam materials. I think I used a small piece of silicone foam. I just cut a small hole in the middle and a slot so I could take it off without needing to remove the filament. It collects the lint nicely. I remembered to put it on when I opened the extruder to clean chips out and found a lint ball in there.
I'm not using a holder, just put it on and the filament feeding into the extruder holds it in place. I'm not at home to take a picture, but you can just barely see it in the picture of the aliens I printed. It is the orange thing on the top of the extruder.
Other people use bits of sponge.
Re: advice on clearing a jammed hotend
May 15, 2013 09:14AM
Re: advice on clearing a jammed hotend
May 15, 2013 09:33PM
If you have a dremel tool, the little round white buffing wheels make a pretty good duster.
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