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How to remove PLA lump that backed up inside nozzle housing UM 2+?

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I've had my Ultimaker 2+ a couple of weeks now and have printed several parts cleanly, both in PLA and ABS. Ok, so now I'm starting to think I know what I'm doing. Then last night I setup overnight print job using PLA. I came down this morning to find the incomplete part had detached from bed and a rat's nest of filament surrounding the moving print head.

Peering into nozzle mount structure I can see a lump of silver PLA backed up inside around the nozzle. Clearly after the part became detached, the filament started backing up. I went into "Atomic mode," cranking the temperature up to 260 C and had a bunch of the molten PLA slowly flow down and around the nozzle. I can still see a lump of PLA back in there. I removed the 0.25 mm nozzle that came out with the threads coated with PLA.

How the heck do I recover cleanly from this mess?

Thanks for the help!

Edited by Guest

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If it's around the outside of the nozzle and you can access it with some needle nose pliers, heat the nozzle upto about 100'C then pull it away with the pliers, a sort of external atomic clean. If you can't access it you may need to remove the fan duct first.

If the nozzle was coated in PLA it would seem that it wasn't quite tight enough in the block, but be careful not to over tighten.

To clear the treads you may need to heat up to 215 and wind in the nozzle to clean out the tread a bit and repeat it a few times, again if it is able to form a small bit you can grab with fine pliers drop the temperature to 100 and atomic pull it,.

Worst case, you will have to remove the block, strip it down removing heater and sensor the use a small gas torch to burn out the filament without melting the brass.

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Thanks Izzy! Unfortunately its the "worst case." I did some preliminary disassembly of the printer head and now can see a big blob of PLA encasing the heating unit as well as the power supply wires and sensor. It will take some time to softer the PLA and remove it. Not a fine experience with my brand new UM 2+!!

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Did the leak come from the block to nozzle thread?

Disassemble the fan duct to get better access, not meaning to blow own trumpet but check out my fan ducts on the YouMagine site, https://www.youmagine.com/designs/um2-fan-duct-v2

Not sure if they fit the new fans but they should do, these allow you to fully see the print nozzle, you can adjust the height from the workpiece, and they swivel out of the way for maintenance.

Also did you print off and use Andes torque tool for tightening the nozzle.

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