Hopefully these notes can help to know what to do in a clog event.
How to recognize a clog
First of all is important to recognize some symptoms of a clog.
There are "generic" universal symptoms but any printer has its own behavior, on mine there are mainly two things that can be symptoms of a clog :
- the extruder "jump back"
Basically the extruder is trying to push the filament but because the clog lose adhesion and the filament jump back, doing a recognizable "click" - under-extrusion (i.e. not enough filament is coming out)
Not necessarily the two things happens at the same time and with the same intensity.
It can start with only some occasional "extruder jumping back" or some occasional under-extrusion, up to a constant jumping back, without any filament coming out.
It can start with only some occasional "extruder jumping back" or some occasional under-extrusion, up to a constant jumping back, without any filament coming out.
This mainly cause no print or the print remains very brittle, with a bad adhesion between layers, often with also a really horrible print (missing parts, holes, etc.)
What to do
Other than start to say very bad words, the first thing is to have a deep breath and be patience.
Then :
- Heat the hot end up to the filament temperature (usually around 200 C if PLA)
- Remove/unload the filament
- Detach the Bowden tube from the hot end
- Unscrew the Bowden tube holder
- Raise the temperature of the nozzle to the top (usually 260 C)
- Use the unclog needle from the top, pushing out as much material as you can
when the needle doesn't encounter anymore resistance put back everything and try.
If still problems the clog is a bad one, so the best thing is to take a deeper level.
Repeat as before, then :
- remove the fan cage so to expose the hot end
- remove the nozzle
- Decrease the temperature around 150-180 C
Keeping the high temperature often ends up having a kind of "gue" that stick everywhere.
Ideally we want all the plastic melt in a single blob. - with something with the diameter of the internal tube, try to push out the clog.
A piece of Bowden tube or maybe a nylon filament.
Looking in the hot end from above you must be able to see thru the internal tube.
Usually in these cases better to change the nozzle anyway, very probably will be impossible to clean it good.
Put back together the hot end, re-screw the fan cage, reattach the Bowden tube, the printer should be back working.
A trick suggested to me when putting back everything, is to screw in the nozzle, then unscrew it little bit, push in the Bowden tube and then full screw the Bowden tube.
In this way there is a bigger chance to avoid gaps between the Bowden tube and the base of the nozzle, one of the primary cause of clogs.
In this way there is a bigger chance to avoid gaps between the Bowden tube and the base of the nozzle, one of the primary cause of clogs.
Cold pull
There is also a technique called Cold Pull that can be used.
I did try but didn't solve the problem, maybe is not working with all type of clog.
In any case taking apart the hot end even if is a longer and uncomfortable procedure, I think is the best one.
I did try but didn't solve the problem, maybe is not working with all type of clog.
In any case taking apart the hot end even if is a longer and uncomfortable procedure, I think is the best one.
A clog
This is a clog example.
On the left of the cent, the actual clog removed from the hot chamber.
On the right a piece of filament that was stuck above the clog.
On the right a piece of filament that was stuck above the clog.
Resources
Of course online is possible to find tons of video and suggestions, this was just my experience.
A couple of good videos covering
A couple of good videos covering
- YouTube - Ender 3 unclog - examples
- YouTube - Unclog techniques
- YouTube - Cold Pull techniques
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