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Filament leaking and oozing above hot tip, filling the area above tip with solid filament material.

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I previously had posted about possibly having the brittle filament from Ultimaker that came with the unit. I asked for a determination if the video I provided was demonstrative of that defect and asked for instructions on how to return the filament for good filament. Tangling has been a constant problem.

Possibly as a result of the tangling, a new problem has developed. The area above the hot tip is now filled with melted filament. I have no clue how to deal with this. I've attached a video showing the situation.


I am happy to get advice from the community, but as with my last post, I am hopeful to get some direction from Ultimaker.

Thank you.


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Having read many threads on this issue I would like to add that in my case ignoring the problem and letting the leak seal itself is not working, I get large blobs appearing intermittently on prints. Heating the tip does not make removing the material easy since there is so much of it it remains solid, and further,, it is wrapped around the wiring entering the area above the hot tip. I have a Ultimaker 2+ that is less than 2 weeks old. I am thinking the leaking problem is more than I want to cope with. I am no longer satisfied with this product.

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This is usually caused by a failed print like you suggested, often because the print did not stick onto the buildplate adequately. I would aim to re-level your buildplate a bit closer. (after you clean your head). This is usually NOT caused by leaking, but actually by the head getting clogged and the material running upwards into the heater block.

This should not be ignored or allowed to 'seal' itself. The heat from the nozzle block will run off into the material and into the fan shroud and continuously drip into your print as well.

To clean the material off your heater block, heat up your nozzle to 90C via maintenance -> advance -> heatup nozzle. When it hits 90 wait a few minutes and then take off the fan shroud. You need to unscrew the 2 screws on either side of the shroud above each fan that goes into the head housing.

Once you do that take off the fan shroud by pulling it downwards. It maybe a bit sticky since the material may be stuck onto it. Sometimes it's easier to remove the nozzle first. (this can be done at 90C with the proper hex nut.

At 90C, the material should be soft enough that you should be able to peel off the gunk that's around your heater block as a whole piece. If it requires too much force, heat up the nozzle another 10 degrees.

Once removed you should be able to put everything back together and it'll be as good as new, cleaner even, its like a waxing for your nozzle. :D.

Once you get the bed nicely leveled this problem rarely happens.

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I think the leaking is because there was not enough pressure on the ptfe. This can be easily spotted. When you have the + models or replaced the spring in the hot end with a tube on the older UM2 models the hot end isolator (the metal part with holes all around) should not be too loose. Rotate it until it's pretty tight.

@sandervg think we still need a proper instruction from um on how to (re)assemble the hot end with the correct amount of pressure...

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My 5 cents about this kind of leaks.

TFT it's actually harder than normal PTFE and can hold much more pressure than normal PTFE (according to Nasa studies) since TFT deformation underload it's less than normal PTFE (it's on the datasheets of the dupont material).

So, my theory. The Aluminium slightly bends under pressure, the x4 long screws keep that tension equal since they pull back the curvature. And overtime of use, the x4 long screws will loose it's tight (or loose fit) as any screw does over time on a hotend that shakes at fast speeds, and that will leave a gap that the filament will find, and leak.

Ofc that doesn't happens much in reality. My hotends (after I got 3 leaks because I wasn't sure how much pressure did the assembly actually need) they are working non stop 8-9h a day. So, super happy with the um2+ design. But also, how much pressure it's enough and when it's too much?

Also, a fix I had to do on my hotends (because I use 1.75mm size tfm/hotend) was to actually use a 2mm drill bit to clean the deformation caused by using too much pressure to leave all fit without leaks.

Just thinking out loud =)

Edited by Guest

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