Blocked pva nozzle

[dbtorchris 0]

Hi guys,

 

I have an Ultimaker  3 extend here and after a couple failed print with dual extrutions, the BB0.4 nozzle is blocked by the botched up PVAs and I cannot flush out the block with hot pull even after multiple attempts. Here are the photos showing how far the cleaning fillament will go in marked with a black marker. Any chance I can unblock the nozzle? thanks

 

[Smithy 1,144]

Seems your print core is also clogged in the cold zone of the core. Normally this part is not hot enough to melt the filament. You can try if you can loosen it a little bit with a needle from the tip, but I think you will need a new print core. 

 

But I just have another idea. The middle fan in the print head is responsible to cool down the silver part. So you can try to heatup the core but open the door that the fan cannot reach the heatsink. Maybe it helps to soften the material a little bit more.

[Framar 38]

If you are to a point of replacing the printcore you have nothing to loose to dissamble the nozzle and cleanit manually (drilling the PVA) and put it back together. I used to to that once and the printcore was saved.

[Phoenine 0]

I met the same problem...

[robinmdh 100]

I've not encountered the situation that a hot pull did not work at all, That does make me wonder if you are doing the hot pull corrctly it is very short not more than a second all the way inside the printcore....
That said I do have some guesses that might work:

• you can try pushing it out while it's extra hot
• use air pressure to push the filament out the other way while the hotend is hot.
  WARNING: if any hot plastic makes it past the PTFE insert and sticks to the metal there it's even more difficult to remove.... also air pressure may make things fly, take the appropriate precautions. (I've used air pressure before to get a clog out, it did work but does not clean much but the clog itself)
• try to dissolve the PVA with water... by pouring a smal amount into the top of the hotend, circulation would be a huge problem though, will likely take multiple attempts....
  WARNING: water and electronics do not mix, be very careful!!!!
• get a small drill bit (preferably used manually) to drill out the filament until you can perform hot/cold pulls.
  WARNING, drilling is likely to damage the PTFE insert or the metal of the hotend as much as the plastic stuck in the printcore.
  
   

This is all my own speculation, and I'm not someone focused on materials.  Some of the methods above would obviously void any kind of warranty, etc.

Good luck!

Edited November 12, 2020 by robinmdh

[Carbon 28]

Heat the nozzle for 5 mins or so, then insert a hot drill bit or a hot Ø2.5mm rod and either push or pull it out.

 

Or try using a HOT AIR BLOW GUN instead....

 

Just thinking of ideas, be CAREFUL!!

Edited November 12, 2020 by Carbon

[geert_2 557]

If regular cleaning would fail, and you are going to drill out the nozzle anyway: maybe consider making your own drill from a 3mm copper or brass rod, or a brass M3 threaded rod? Brass is less hard than steel drills, and thus far less likely to damage the nozzle internally. Ideally, give the tip of your self-made drill the same shape as the internals of the nozzle-tip.

 

So your custom drill should be softer than the nozzle-internals, but harder than the plastic you want to remove. (Maybe this would be a good tool to provide standardly with all printers?)

 

I sometimes use a brass M3 rod to clean the side-walls of a nozzle, if there is too much dirt accumulated. It scrapes the sides like a soft file, sort of. But that probably won't work for you, since you need a sharp tip to cut through the PVA from the top, not the side. So you have to reshape the M3 rod on a grinding disk, and then cut big cutting-paths in it (I dont' know the correct name) with a thin nylon cutting disk on a Dremel, so it can bite into the PVA and remove the loose debris.

 

Also, for cleaning the nozzle tip (=0.4mm on my UM2), I have modified a thin injection needle: I cut off the sharp tip and round the edges. Now I can insert this from the bottom into the hole, to remove partial blockings. But this alone won't help if the whole nozzle is blocked of course. Don't use a needle with sharp tip: this will damage the nozzle by biting into it.

 

See the pics:

 

Brass M3 thread, with rounded end to minimise risk of damaging nozzle internally.

 

Gently scraping the side walls of the nozzle, to remove accumulated dirt. Always gently, never use brute force.

 

Fine modified injection needle.

 

 

Edited November 12, 2020 by geert_2

[dbtorchris 0]

Thanks guys . Sorry for the late reply. But I managed to dissemble the print core and cleared the blockage.