Unable to unscrew nozzle after clogged feed for several hours unattended.

General LulzBot TAZ
1

I think I know exactly what happened but I wanted to get more info if possible.

  1. I started a 9 hour Print just before going to bed.
  2. 1 hr into the print I came back and everything appeared fine.
  3. I woke up to what appeared to be a simple sheer of the filament at the Feed point so the printer didn’t finish the job.
  4. I powered off the printer.
  5. ate breakfast.
  6. came back powered up unit.
  7. preheated for ABS.
    8 . Nozzle - 230 Bed -100
  8. after 10 min I came back to only find the bed hot and the nozzle cold and showing ~20c
  9. I repeated the process several times to see what was happening.

< at this point I decided to take off Tool head and the hot end to see what was wrong >

Upon Examination noticed that the Heat Resistor, 4.7 Ohm was moving very freely so I decided to straighten the wires, and gently slide out the resistor and then take a look at the resistor. It appeared to be very malformed.

![20150906_105122[1].jpg|4128x2322](upload://i4ytr2tl2WKZKyj0fWX2UM7BWie.jpeg) ![20150906_105135[1].jpg|4128x2322](upload://3NlsmdjGDXPTpieEEjRps7Ixxxg.jpeg) ![20150906_105207[1].jpg|2322x4128](upload://utYiZKtH7SXMnVQ97XyUnixGao3.jpeg) ![20150906_105212[1].jpg|2322x4128](upload://od4rB5WOvLutPgaAQMv1eXZUrou.jpeg) I attempted to lightly unscrew the nozzle at this point and it would not budge. It seemed to be chemically welded to the hot end.

so i tried again with a bit more force and snap.

At this point I have basically destroyed part of my hotend trying to get what appears to be a chemically welded Nozzle attached to the threads of a Budaschnozzle 2.0 Threaded Extension tube off. and want to understand why it happened.

so to fix i bought

  1. Nozzzle .35 - 19.00
  2. Heat Resistor, 4.7 Ohm - 4.50
  3. Budaschnozzle 2.0 Threaded Extension ( sadly out of stock ) - 11.00
  4. Budaschnozzle 2.0 Heater Block - 15.00

I salvaged all other Parts of the hotend minus the Tube, Heater Block, which is also chemically welded to the tube and the nozzle which has part of the tube stuck in side of it.

I know they are supposed to be replaced every so often but this just seems a bit excessive with how this thing welded together. looking for ways to prevent this going forward.

Right now I know the printer works because I installed my Flexy Dually head and it is printing just fine. I was hoping that i was not going to need to use this head right away as it was for another project but tight now it is the only head i have that works.

its at lest a semi not so expensive fix but i want to know for the future what i can do to keep this thing going as long as possible.

2

I am sorry to see about the Budaschnozzle! I do have a couple suggestions that may help the longevity of the hotend.

The 4.7ohm is originally designed to change current and voltage within electronics. As a by-product they will produce heat. As they are never designed to generate heat, they will fail from time to time. We stay true to our reprap roots by using these, as they are fairly easy to come by and inexpensive (~$1.00 each when purchased through Digikey or Mouser.) Directions on replacing the resistor are here.

The threaded extension and nozzle tip need to be heated before attempting to remove. Filament can get between the threads, acting like cement when cold. We recommend heating to 160c-180c, then turning off the printer before attempting to remove the nozzle. This allows the filament to be molten enough to be removed. If you heat higher than this, you can cause the aluminum extension and nozzle to expand so much they will seize and be impossible to remove.

I hope this helps!

3

Would it not be easier in the long run to go to the Hexagon hot end or the complete V2 head?

4

Aluminum on aluminum in heated parts is never, ever a good idea. I broke my Buda style hotend 4 out of the 5 times I tried to take it apart.

I use to work in building maintenance and some boss had the brilliant idea to buy cheap aluminum based lights for our place (80 light fixtures) and the sockets were also aluminum. Needless to say for the next 5 years we were fixing or replacing fixtures as the aluminum base on the bulb would fuse to the socket.

I switched to the all metal hotend (not aluminum) and now I don’t dread switching nozzles or just opening it up.

5

The Hexagon head is aluminum, nozzle is brass. Should not be a problem.

6

I agree. I wouldn’t spend any money repairing the Budaschnozzle. Get yourself a hexagon or E3D and be happier!