Filament Jammed During Failed Cold-Pull


While attempting to remove the filament currently loaded into my direct drive Lulzbot Mini 2 with a cold pull my filament is now jammed in place.

I loosened the idler then set the hotend temp to 210 degrees, once the temperature approached the setpoint I tugged on the filament and it retracted about 1cm then jammed.
As far as I can see the filament hasn’t yet cleared the hotend and is likely snagged or jammed up in the hotend.
Attempting to retract using the extruder gear just grinds away at my filament with the hobbed bolt with no movement.
Leaving the temperature set to 210 degrees my nozzle isn’t oozing or dribbling like it sometimes would, so there appears to be no pressure in the hotend. Trying to press the filament back toward the extruder also has no movement.

I suspect the jam may be in the cool zone of the heat brake so I wanted to ask if it was a good idea to manually disable the extruder cooling fan so that I could have heat creep back up the filament path to try and soften the obstruction. Does anyone know if there are any bad consequences to this I may have overlooked before I try it?


Hi Spookee,

Other than any plastic parts attached to the top part melting I cant see too many others,it would definitely be worth slowly turning down the fan speed though, so you can catch anything bad. If you have some tools it might save you time disassembling the hot end completely.

If you cut the filament short, remove the nozzle you might be able to push it though? A bit of a long shot imo


Hi Liam and Spookee,

I agree, slowly reducing the fan speed should help, although sometimes depending on the filament and previous filaments used in a hot-end, there can be burnt pieces of filaments or breakdown from the teflon tubing running to it that slowly clogs up your hotend.

It’s quite rare to have to do so, although if you haven’t already, opening up your hot-end and checking inside it with a torch for any debris (depending on the printer, I find compressed air works quite nicely to clean it out, although needles work well for catching and breaking up old burnt filament) to make sure that you’re getting decent and consistent heat transfer into your filament certainly can aid with flow and preventing blockages such as that you’ve described.

Hi Spookee,

Interesting problem! Did you have any photos of your toolhead so we can work out what the construction of it is? I’ve got a couple lulzbots that had a similar issue to you (a blockage that will go neither up nor down)

My printers are out of commission for a while, so I’d be happy to tear down my toolhead and point out where my errors usually occured.


Hi James

I’ve torn it down and confirmed the blockage is definitely somewhere below the extruder.
I’ll definitely remember in the future to retract first, and cold-pull as a last resort.
I tried to heat the printer to 210 and unscrew the nozzle but lacking proper spanners I gave up quickly as I was just slipping and rounding the nozzle. It’s really stuck and I can’t get the nozzle unscrewed.

I’ll ink the teardown instructions below for reference.

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A needle would be just the tool for the job, I’m not sure if I have one thinner than 0.25mm though as this is the SL tool head so it’s super small!

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Hey Spookee,

Hmmmm, I have had filament solidify on the area around the nozzle orifice before, so this may have happened on your nozzle threads perhaps? Might be worth taking the hotend to 235 or so, somewhere where ABS would soften, but isn’t too likely to carbonise.

FWIW, I used a large shifter on my nozzle on my lulzbots, and later started using a 7mm socket. You might end up unscrewing the heatbreak too (small threaded rod that sits in between the hot and cold side of your hotend) if it’s really stuck.

If you reeeeally get stuck, you can just take apart what you can and heat gun it (I’ve done that to get blobs of filament out of my toolhead)

Hope your printer gets on its feet soon!

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