How to Unblock a 3D printer Extruder

Whether you buy a 200$ or a 2000$ 3D printer, if it uses fused filament, then sooner or later the extruder will clog and will have to be cleared.
Always watch the extruder in operation, warning signs of a partial blockage are
• Extruded material is thinner than usual
• Extruded material contains ‘lumps’ or is uneven or even bubbles
Some models are more prone to clogging than others and the feed of filament into the extruder has a lot to do with it. If you always ensure cleanliness around the feeder, don’t handle the filament more than is necessary and clear away dust on a regular basis, you will minimise these annoying events.
From my own experience I find that PLA is the most frequent filament to clog and I suspect the water absorbing characteristics of this material may have a bearing on the tendency to cause clogging, so keeping the filament covered or enclosed, not handling it at all except when loading and keeping it in its delivery wrapper right up to its use, is a good way to minimise problems.

Technique 1

One effective method of removing solid material from the extruder is to use another filament to pull it out. Nylon is very strong and the best one I’ve used so far:
• Heat the extruder to normal working temp around 200C
• Introduce a nylon filament and allow it to start melting
• Switch off the heat or reduce to about 120 C
• Pull the filament out , attached to some blocked up material
• Repeat until completely cleared
Each time you repeat the above more of the blockage should come out , eventually you should see the last piece, with the much thinner part which actually entered the nozzle. Three attempts is usually enough to clear my own, but I must admit my own Ultimaker2 is not a frequent blocker and usually manages many many hours of printing between problems, in fact it has only blocked up when starting up a new print when the old filament has not been allowed to run out completely.

Technique 2

Another technique which works is to overheat the extruder by about 10 to 20% then use a stiff wire of the right size to free up the blockage. Telephone cable is always a good bet, fairly stiff and easy to run in and out of the extruder hot end. Most ABS and PLA blockages will clear easily using this.

Finally

in the worst cases of ABS blockage, remove the nozzle and put it in a bath of Acetone for half an hour, then using a blowtorch heat it up and use the wire to clear everything out. If phone cable iisn’t strong enough try a guitar string, the thinnest strings ( E or B ) is usually ok for 0.4mm nozzles at about 0.15mm.

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