TAZ 5 Hotend Clogged

Our week-old TAZ 5 has been printing parts in white ABS (from Lulzbot) without any trouble, but just yesterday it decided to stop extruding filament altogether, even in air. This seemed to indicate a clog, so we tried doing some cold pulls, which came out looking quite ghastly:

At no point did we see anything resembling the inside of the nozzle, and I’m not sure if those three little cavities are to be expected or not. Based on the 3D diagram of the nozzle, I would say they’re not. The hotend did, however, go from completely clogged to just partially clogged, as you can see from this picture:

Rather than flowing freely as it did before, the extruded ABS now forms curly lumps around the nozzle tip. I’ve already spoken to support about this and aside from doing more cold pulls, they had me try a print of the Rocktopus, which came out looking like a hot mess:

We don’t want to resort to soaking the nozzle in acetone, but are there any remaining options apart from having a replacement sent?

I’m also wondering what could have gone wrong to cause this in the first place. We’ve only used the green PLA that came with the machine and then white ABS ordered directly from Lulzbot.

Removing the nozzle is actually fairly easy… I don’t think its supported by Lulzbot though.

If continuing with the cold pulls, make sure to try and extrude a bit of filament manually when the hotend is at temp… then cool down and do the pull.

There is also cleaner filament.

If you want to venture into removing the nozzle:

  • Protect the PEI and glass from the hot nozzle and tools. I used a silicone pad / trivet
  • Remove filament - cold pull or at temp
  • Heat hotend to 165C keep this temp until nozzle removed.
  • Use a 17mm or 18mm to prevent heater block from rotating, use a 7 or 8mm wrench to remove the nozzle. I used the 18 and 8 combo since that’s what I had on hand.
  • Unscrew the nozzle clockwise. If unsure, righty tightly, lefty loosey’
  • The nozzle will be hot, so make plans to “catch” or hold the nozzle. I used large locking forceps or let the nozzle drop onto silicone pad if rated to 200C. A crescent wrench or vise-grips would work also.
  • Let the nozzle cool down
  • Optionally: Remove as much filament from nozzle. I drilled out the filamemt with a low powered hobby drill an appropriate bit. Don’t damage the interior of nozzle.
  • Soak in a jar of acetone. If impatient, soak for 10-20 minutes and dig put softened ABS with toothpick or suitable thin object (is drill bit, fork, bamboo skewer).
  • Shake every so often and use new acetone when it gets cloudy
  • When acetone is clear after a soak, your nozzle should be clean
  • Use a strand of wire to thread through nozzle opening to ensure blockage is cleared.
  • One final soak and shake in acetone.

Replacing nozzle on heater block:

  • Protect your build plate as above
  • make sure the nozzle is dry of acetone… If you have denatured alcohol that will help, but the acetone should evaporate on its own.
  • heat hotend to 165C.
  • hand thread (Be careful, heater block will be hot) the nozzle to the heater block… Must use fingertips so as not to damage the thread. There should be very little resistance when screwing in the nozzle. You’ll only have 5-10sec before the nozzle gets too hot, just let it cool down for a minute and try again.
  • Once threaded, use the wrenches to tighten.
  • Continue heating to 240C and re-tighten.
  • Let everything cool to 20-30C.
  • Heat back to 240C
  • With idler open, push filament through by hand.
  • Should yield a nice straight extrusion.
  • If not, repeat the cleaning.

As an added measure while the nozzle is off, heat hotend to 230. Use filament to push any leftover material in the heater block.

Hope that helps!