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Korneel's method for cleaning Hot-ends (UM2)

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if there can be an Atomic Pull, there can be Korneel's cleaning method ;)

The Issue;

I had 1 printer (yes, another UM2 has been bought) and i have several hot-ends. after a while i always had something happen with the hot-end (i have about 4000 hours on my printer). the printer is running almost continuously and i switch filaments quite often. this means that every now and then the hot-end just "junks up". there is debris all over it, ruining new prints and just attracting new burned filament. i swap out the nozzle\hot-end and i move on.. but this also means i have a couple of spare hot-ends. i tried different methods of cleaning them and i looked for suggestions. in the end, i came up with a consistent working method that is easy to do, cheap, and accessible to everyone.

what do i start with?

the nozzles usually look like this:

WP 20150227 004

WP 20150227 003

WP 20150214 007

WP 20150214 003

as you can see, there is burned\melted filament everywhere, in the hozzle, in the screw (hole) in the metal coupler, everywhere. in the past i would burn it off, but this would leave burned particles on the nozzles and ruin the thread. i had to then clean it off with a scalpel and it wasn't much fun.

so what do you need?

(PS i did this in the kitched, underneath the cooker hood running full blast since it was cold outside. always use good ventilation when doing this!)

-a decent underlayment where you can have plastic drip on. i used thick cardboard

-(almost) pure alcohol

-an old cup

-small plyers

-a decent gas burner

-a powder extinguisher or a fire blanket to put out any fires you might cause. DO NOT USE WATER!

i used this:

WP 20150227 006

WP 20150227 007

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poor the alcohol in the cup so there is enough to immerse the nozzles and other pieces. make sure you do this below the hood, alcohol easily dissipates and the smell isn't good for you. it's also very flammable.

take the pliers and hold the nozzle or other part you want cleaned on a clean portion of the piece (for the nozzles i use the heater hole) and hold it just tight enough. by clamping to hard you can deform the piece.

put the gas burner on a concentrated flame and easily\slowly move over the piece so that the plastic starts burning\glowing. if the piece you are trying to clean starts to glow red you are burning to hot and start deforming it! copper will not easily deform at the heat you need to burn out the plastic so you should be good. there will however always be people that try to emulate the heat of the sun.. so hence the warning ;)

if the plastic starts burning just let it burn.. make sure you do this below the cooker hood or somewhere else well ventilated. these fumes are toxic.

WP 20150227 009

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after you have burned off the plastic make sure it is no longer burning or glowing, then drop it in the cup of alcohol. you'll see it sizzle. move it around with the plyers then take it out and tap it against your solid underground. you'll see a lot of black junk coming off of it.

wait till it dries up then repeat the process untill it is clean. note: nozzles that you have burned more often will leave a bit of black residue.

WP 20150227 012

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make sure you can look through the nozzle! you should be able to see a very small hole.

once you are satisfied, you can simply polish the nozzle up..

before using the nozzle again make sure you do an atomic people (Taulman Nylon is the best material for this!) to remove the final pieces of burned filament. your nozzle will be as new again :)


you can use this not only for the nozzle but for all metal pieces that have plastic residue.


this is the junk you just took off;

WP 20150227 014




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Instead of a cardboard box, you might want to use something that's less likely to catch fire...


Well. That would be less fun.

Yes a metal plat or something would be preferred. I user cardboard since it would not burn from a heated nozzle nor does it simply catch fire.. But you are right, metal is better

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Try using jeweller's pickle (a weak form of sulfuric acid) heated in a ceramic slow-cooker instead of the alcohol. You can get is as dissolvable granules in jeweller's tools/supply shops. It works a treat on brass and unless you leave the part in for days it does not harm the surface of the metal. I would also use a fire-brick while heating the hot end, and just place it on top of a honeycomb firebrick instead of holding it (or use a third hand).


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