Hot end / Nozzle clogged

I just bought a LulzBot Mini a week ago and have been printing a few hours each night. I started with PLA (@205), and have been using ABS (@240) for the past 2 days with no issues until last night. At the start of my print, the nozzle clogged, and I followed the instructions here - - to clear the clog, and was able to continue printing without any problems. When I tried to print today, the nozzle was clogged again, and tried to repeat the unclogging process, but this time the filament broke off at the base of the heat sink, and there is no way to pull the filament back out.

Is there anything i can do at this point to clear the clog?

First I would contact customer support and just get a replacement without doing anything to void your warranty. What I do when this happens is disassemble the whole extruder assembly until I am left with just the hotend. Heat up the hotend then take a 2.5mm allen wrench and use it to plunge the filament down and out of the nozzle.

I’m guessing you meant, the filament broke at the base of the extruder near the top of the heatsink… If you can see the filament, try grabbing it with tweezers or locking forceps. Heat the hotend to extrusion temps and pull the filament out.

Try the cold pull again to unclog.

I contacted support and they had me RMA the toolhead.

It just seemed like this should be a fairly common problem, so I wasn’t sure if there was anything that I was overlooking. Not having a baseline to compare against, its also not clear how much force should be needed to pull out the filament when at extrusion temps. Even straight out of the box, it felt like the ship-with HIPS was not wanting to pull out smoothly at temp, almost catching on something in the hot end as i followed the instructions to swap filament. I’m not sure if that’s normal, or an indicator that something may have been wrong with the hot end.

Filament at extrusion temps should be pretty easy to pull out of the hotend. Make sure to unlatch the idler.

They should be easy to pull out. However, that cheesy little squirrel cage fan doesn’t always cool enough to prevent a little heat creep jam that makes it difficult or impossible to remove the filament. I have fought this problem with one Mini and two Taz 5s. They put a larger hotend fan on the Taz 6 for a reason!

There is a brass insert at the top of the extruder that can prevent the removal of the filament if the filament swells or is soft enough as it passes through this area. Which will cause a widened ring that locks the filament in the top of the extruder. This requires a disassembly of the hot end to clear this type of plug. This is usually due to the filament being pulled out and pushed back down compressing the filament and making it bulge just in the right point to flare the filament into the joint between the insert and the steel tubing.

The brass insert is where the Bowen tube fitting would mount if that was the type of hot end you had.

Thanks for all of your input - I did unlatch the idler before attempting to remove the jam and the hot end was at extrusion tempurature. In regard to this comment:

Are there any guides or recommendations out there for upgrading that little hot end fan? I haven’t looked at the Taz 6 design yet, but is this something that could be adapted to the Mini?

I worked off of these parts -
I believe the parts are from the Lulz repository.
You need a new extruder to provide the mounting points for the new fans.
I think I read that it was the “improved” design for the Taz6.

Best regards,

PS - I just realized you are working on a Mini… )c8

There’s a shroud design on thingiverse that fits the mini, and allows a 25mm fan to be used. One of the forum members here (coparatech) has reported good results with it.

Yep, it works great and is a direct replacement for the mini squirrel cage fan. It works on the Taz 5 and Mini. Here is a link to killacycle’s original file:

I’ve got a 25mm fan on order, but hasn’t arrived yet.

I got my RMA’ed toolhead back a few days ago and printed a small 30 minute job to confirm the printer was working (using a new spool of ABS, to remove that variable), and everything printed fine. I ran another 2-3 hour ABS job this afternoon with no issues during the print. I went to print a second job about an hour later, and I’m seeing the same problem as I was before the RMA - the filament is not extruding and the hobbled bolt is grinding against the filament. I’ve brought the hot end up to temperature and tried both pushing the filament and pulling the filament, but can’t get it to move. Its incredibly frustrating to have these problems right out of the box.

Is there something that I’m possibly doing wrong with my print process? I can’t imagine that the heat sink fan is so undersized that my printer is unusable without modifying it. Thanks in advance.

Talked to tech support, and my problem was almost certainly heat creep.

With their guidance, I was able to remove the filament. To clear out the stuck filament, I needed to point the fan away from the heat sink and follow the standard clog clearing process. There was a noticeable ridge around the filament where it had expanded in the heat sink. Lulzbot tech support were awesome - thanks for the guidance!

I’ve been experiencing what i think is heat creep on my mini as well. I can now print short things with HIPS fine now, but tall objects still elude me and the layers become thin strong thin strong and then finally cobwebby at the top when i finally cancel my prints. PLA is worse.

I’m about to test print a Lulzbot hexagon fan replacement i just designed for 40mm fans. It’s not on thingiverse yet. If it works i may design one for 30mm fans as well. None of the other designs on thingiverse seemed quite right to my liking or fit the lulzbot version of the hexagon.

I saw the new fan design for the TAZ 6 as well. Looks nice, but that big round thing just didn’t look like it would fit on the mini and hit the x-axis homing switch quite right, so i didn’t try it. But i would be curious if someone can confirm that it does work on the mini.