After a few months of FlashForge use one issue has consistently cropped up.

The extruder assembly has for the most part been great, and extremely reliable.  The only challenge I still get on occasion is heat soak creeping up the Teflon tube inside the extruder, which results in a clog. There are two ways this can happen.  One is just from the machine sitting idle after a print while the hot end assembly is still “warm”.  The other can occur if you are printing at very slow speeds. In this case the filament in the extruder is not purged as quickly, so the heat energy is not being expelled fast enough to control the melt zone.  This can result in the heat traveling up the filament, and melting it up much higher in the tube than it was originally intended to do.  You end up with a filament jamb when heat travels far enough up the filament to distort it as it enters the heating tube.  At this point it basically stops itself like cork in a bottle, and you have to take the fan and heatsink off so you can get in there with small needle nose pliers and remove the clog.

The other issue is the Teflon tube in the hot end.  It clogs after some time, or eventually loses the compression seal between it and the nozzle tip, resulting in leaks around the joining threads and/or filament jambs. As far as I can tell this is mostly the result of issue above,  running low quality filament (NOT WORTH IT!) and/or filament with a much lower melting temp than the standard 230 C extruder temp.  If you have saggy prints, you are probably running your nozzle too hot.

Teflon tube in the hot end clogs from PLA being left to bake inside it.

Teflon tube in the hot end clogs from PLA being left to bake inside it.

I seem to have completely fixed the aforementioned problems  by only running filament from reputable suppliers (We have had good luck with “JustPLA”),  and changing the way I do filament changes.  The latter seems to be extremely effective at minimizing the amount of dis-assembly I  have to do.  My solution?  PURGE, PURGE, PURGE!  Every time you finish a build, purge out a good portion of material (at least an inch or so on the inboard side) either by hand, or using the “LOAD EXTRUDER”  function in the utilities menu.  Then immediately pull the filament completely out of the top of the extruder.  This prevents the filament from sitting in the hot end and baking into a rock hard clog, often rendering the Teflon useless, and sometimes the nozzle as well.  Before re-loading the filament, make sure to clip off the funky looking end so you always start with a clean constant-diameter filament.  As soon as I started doing this simple step, the majority of my extruder issues completely dis-appeared.

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3 Comments on Purge Your Hot ends!

  1. bailey gribben says:

    how did you unclog the extruder? Do you have a video? I have a flashforge creator pro and both of my extruders are clogged.

    • ganter says:

      Bailey, I am assuming you are using PLA. We unclog extruders any one of four ways — 1.) buy quality filament, 2.) try using the small wire/needle/drill trick. Bring the extrude to temperature and carefully push small wire (0.3-0.35 mm) into and pull out of nozzle., 3.) push a 1.5mm Allen wrench down from the top. please go easy when you get to the bottom you can damage the precision nozzle hole, 4.) take the extruder assembly apart. remove fan and motor. to check out what’s wrong. next remove nozzle (you do this HOT). please wear protective leather gloves. now look from top and bottom to determine the clog location. replace PTFE tube, etc.

      Always keep spare nozzles and PTFE tubes around. They are low cost and often save the day.

      Lastly, you may need to “burn out” your nozzle. Find someone with a kiln or annealing oven, give it 3-4 hours at 400C or 800F (think burn out the organics but not melt the nozzle).

  2. glen says:

    Use a Guitar wire think 04 get a butane burner to heat tip and pock wire thru hole…drill out tube to 4,8 mm and get some fibreglass insulation tubing from some electronic shop slide over teflon save heat transfer.

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