After something like 150 hours of 3D printing leading up to Christmas it’s no wonder that my Cocoon Create decided to extend its holiday with some down time to kick off 2017. There have been 2 problems to do with extrusion that I’ve come across, and thought they might be handy to know how to fix for others with this printer, or indeed any of the many derivatives of the original RepRep Prusa i3 which this printer is based off.
The top image shows the first problem which I noticed after some jamming and issues swapping out filaments – basically a build-up of filament “powder” over time from the gear grinding it when it’s been jammed. This one’s a nice easy fix, just a cleanup and a reminder to open up the extruder occasionally to keep things clean. If you’ve never opened the extruder before it’s nothing scary, just 2 bolts on the left where the fan is mounted to the heat-sink which opens the whole thing up as shown above. You might be surprised how simple the whole mechanism is.
After fixing this problem and doing a couple of prints, I then noticed the filament was getting jammed again and I couldn’t push filament through the nozzle no matter what I did. Opening the extruder (same process as before except now removing the small screw on the right of the metal block to release the actual nozzle) the problem was pretty clear – a clog in the PTFE tube which you can see above. A lot of people are surprised to open their extruder and find a plastic tube inside, and this is the first time I’ve really had a problem with it. This tube is made from PTFE, basically Teflon like in your non-stick frypan, and seems to serve a couple of functions from what I’ve read online:
- it stops heat from the nozzle climbing too high into the extruder and prematurely melting the filament, which would cause serious clogs.
- being non-stick, it helps the filament keep sliding smoothly down to the nozzle without sticking as it gets warm.
A very cheap, simple part that has a lot of responsibility. Mine must’ve gotten worn out or slightly dislodged during my last attempt at fixing the extruder. Thankfully my printer came with 1 replacement, which I cut to size (make sure both ends are nice and square so that there are no gaps for filament to get caught in) and now I’m up and printing again with no problems. Also I’ve jumped onto Ebay and ordered a 2m length of PTFE tube (inside diameter 2mm, outside diameter 4mm) from China for $2.50 – I recommend anyone who has a 3D printer with this part order some PTFE tube as backup, it’s very cheap but if you need to buy something locally in a 3D printing emergency, prices look at least 10 times higher. For a couple of dollars it might just help keep you sane.
Some good forums discussing PTFE tube issues:
- https://groups.google.com/forum/#!msg/flashforge/8RBXZhlggvM/C8wP4w6hzlYJ
- https://www.reddit.com/r/3Dprinting/comments/2hca7w/ptfe_teflon_tube_in_hot_end_what_does_it_do_is_it/
- https://groups.google.com/forum/#!topic/flashforge/8RBXZhlggvM/discussion
I’ve previously written about another type of clog where filament breaks off inside the extrusion tube as you’re retracting it, and you can’t force a new piece in – check out the post here if this sounds like what you’re experiencing.
Happy 3D printing, happy new year.
– Posted by James Novak
edditive blog 
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