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AA 0.25 Printhead


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Posted · AA 0.25 Printhead

I have 2 AA 0.25 print heads and both are clogged and no matter what I try I cannot get them unclogged. I tried all methods of cleaning, cold, hot and atomic pulls.

Anybody have other ideas?

 

Thank you

ft

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    Posted · AA 0.25 Printhead

    Is it PLA?  I hope it's PLA.  There are lots of ways to clean these but cold pull is the easiest.  I know you said you did that.  Here's what to do - somethin in these instructions is bound to be different.  However if you have a 0.22mm hypodermic or accupuncture needle it helps quite a bit (if you are in USA I sell them cheap).

     

    temps are for PLA

     

    a) remove bowden on print head.  Push the head to the corner so you don't bend the rods. 

    b) Heat the core to 180C.

    c) Push a piece of filament (around 5-10 inches or 10-20cm) in through the top and down through the trumpet.  Push pretty hard - like 20 pounds of force (lift something that weighs 10kg/20 pounds for a reference).  You can stop pushing as the temp falls below 120C

    d) cool to 90C.  While it cools maintain a few pounds (1kg) of pressure.

    e) when it reaches 90C pull up.  Hard.  Hard enough that you have to hold the printer down from lifting off the table with the other hand (again - important that head is in corner so you don't bend rods).  If it won't come out, set the temp to 105C.  Take a rest for 2 seconds but before temp reaches 100C start pulling again.  Hard.  If it still won't come out try 110C.

     

    If the PLA comes out easily then you didn't go cold enough.  Do steps b through e but instead of 90C go 5C colder

     

    If the PLA won't come out at all obviously you raise temp.

     

    Ideally you get the shape of the inside of the nozzle - including the 0.25mm diameter final hole.  Yes it's not that hard normally to get that as well.

     

    Some other tricks.  Some people go down to room temp and twist the PLA.  Or you can try 80C and twist/pull at the same time.  I don't normally do this but it seems to work well.

     

    Other tricks:

    While it's at 180C push a needle through the tip of the nozzle - the idea is to push any clog (think grain of sand) up into the plastic in the main chamber of the nozzle to make the cold pull work easy.

     

    You can disassemble the core and separate the nozzle and burn everything out.  Try not to get it cherry red hot (around 500-600C).  But get it hot enough that it smokes and/or flames.  Stop adding heat if it flames.  Do a cold pull after to get out all the ash and newly generated chemicals. 

     

    There's a video I posted on how to disassemble a UM core on youtube.  Search for "UM3 core disassembly"

     

    If you get the brass over a certain temp it will be weaker afterwards.  But that's mostly fine.  It's a little easier to damage the brass if you overtighten the nozzle when putting it back together.  But it's still reasonably strong.  Much stronger than plastic.

     

     

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