A 'cold pull' is a technique for cleaning your printer’s nozzle and hotend from any material that may be stuck or burnt inside. You can also use it to clean your hotend during your usual maintenance routine.
The cold pull should be made if your nozzle is only partially clogged, and some filament is still being extruded. If the nozzle is completely clogged, please check the Clogged nozzle guide.
If you are using Nozzle X, do not use the cold-pull method; only cleaning filament.
Automatic cold pull
Have at least 30cm of PLA available when making this procedure. Then, navigate to LCD Menu -> Control -> Cold Pull.
If the nozzle is heated, the printer will wait until it cools to 36 ºC. Then it will heat the printer to 80 ºC. After that, the printer will unload the filament automatically at that temperature.
To finalize the procedure, remove the filament by hand, pulling it upwards. There might be a slight resistance, if the filament is stuck, open the idler lever.
Manual cold pull
To access the top of the extruder, push up the bowden bend and unscrew the metal fitting.
Go to the printer menu in Settings -> Filament Sensing and toggle off the Filament Sensing.
Go to the printer menu in Filament -> Load Filament -> PLA, and load the PLA filament from above the extruder.
Open the Idler Swivel.
Go to LCD Menu -> Control -> Temperature -> Nozzle Temperature and set the temperature to 270 °C.
Once it has reached 270 °C, push the PLA filament in until it starts pouring out of the nozzle.
Stop heating by pressing Cooldown in the LCD Menu -> Control -> Temperature -> Cooldown, or by pressing the reset button.
Continue manually pushing the filament down until the temperature is too low for it to melt and come out (around 170 °C for PLA). The nozzle has to be filled for the cold pull to be successful. Grabbing the filament with pliers and carefully pushing it down can help.
Pick away any extruded material from under the nozzle so nothing is obstructing the pull later on.
Wait for the temperature to reach 100 °C. As soon as it reaches 100 °C, grab the filament with pliers and pull it slowly but steadily out of the extruder. Make sure to pull straight upwards, not sideways, or the filament can break inside. Hold the extruder with your other hand.
Don't stop until the filament is completely pulled out from the extruder.
Close the Idler and the Idler Swivel.
Screw back the metal fitting and push the bowden bend back down.
Results
On the tip of the filament that has been pulled out, you may see remnants of the previous material(s) you have been using or some burnt dirt that has settled in the nozzle. You might want to repeat this procedure several times until the filament comes out clean.
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Can more information on the automatic cold pull be provided?? Do we need to disassemble anything? 30cm of PLA fed from where? manually pull it upwards? how if the filament will use the standard tube to enter the nozzle. These instructions are confusing.
If you're doing an automatic cold pull I have had success in feeding it from the normal setup and just rewinding the spool once it is done to pull it out. Then snip off the messy end.
For a manual pull, the written advice in the article is correct.
Hi, why do you advise to unscrew the fitting? I only remove PTFE from fitting to make cold pull. I do not tweak sensor detection, only set manually high temp if I need to push a partial clog. This is excellent technique also when you switch from black PETG to orange : there is much less purge to be done to get real orange. I apply reasonable but steady vertical pressure with plier starting from 50°. It come around 70 with PLA on the MK4. I did not checked T°C with Core.
Indeed, I regret Core to disengage filament to make the nice tip. This is probably for MMU users. In my case it is highly counter productive as it requires manual purge, cool down, then cold pull. An option to skip nice tip would be great,
Well I was never able to remove the PTFE tube from the fitting, somehow its permanently fused to it. I hear this from many others so unscrewing is the easiest way. I printed a thumbscrew for that to make it easy. Maybe there are better fittings that work without unscrewing.
To remove the tube, you have to push _down_ on the black collet, while simultaneously pulling out the PTFE tube. It still requires some force to get it going, but eventually it does.
Without pushing it down, the collet instead tightens around it as you try to pull the tube.
I used to have the same problem as you until someone told me the right way to do it. It's pretty counter-intuitive if you've never seen those types of fittings before :S
Yes AND what to do next if you can’t complete this task as I’m currently unable to and don’t know what to do next. Was told to do a cold pull, well I can’t and don’t know what to try next.
11 comments
Do we need to disassemble anything? 30cm of PLA fed from where? manually pull it upwards? how if the filament will use the standard tube to enter the nozzle.
These instructions are confusing.
For a manual pull, the written advice in the article is correct.
why do you advise to unscrew the fitting? I only remove PTFE from fitting to make cold pull. I do not tweak sensor detection, only set manually high temp if I need to push a partial clog.
This is excellent technique also when you switch from black PETG to orange : there is much less purge to be done to get real orange. I apply reasonable but steady vertical pressure with plier starting from 50°. It come around 70 with PLA on the MK4. I did not checked T°C with Core.
Indeed, I regret Core to disengage filament to make the nice tip. This is probably for MMU users. In my case it is highly counter productive as it requires manual purge, cool down, then cold pull. An option to skip nice tip would be great,
Without pushing it down, the collet instead tightens around it as you try to pull the tube.
I used to have the same problem as you until someone told me the right way to do it. It's pretty counter-intuitive if you've never seen those types of fittings before :S
thx guys for your work
The automatic cold pull