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UM3 Heat Creep on Filament causing seizing

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Posted (edited) · UM3 Heat Creep on Filament causing seizing

Hi all,


I've got a UM3 and recently changed to a new print core (AA) after having one fail to a print flooding the head.


I'm getting heat creep on two different PLA spools in the nozzle which causes the filament to expand in size slightly causing it to seize and fail to extrude.  This in turn causes the extruders to detect a flow issue and pause print.  (I have S5 feeders with flow sensors and modified configs on my UM3)


After print pauses I pull the bowden at the print head, snip off the expanded portion, reinsert bowden and it continues to print for a while.  Eventually it will happen again and I repeat the process.


My retraction settings are pretty low at 3.5 mm - 4mm/s.

Retraction speed is 40mm/s.


Previously my settings were 4.5mm/s for retraction length and 25mm/s for speed.


Anyone have any suggestions on what could be the culprit? 



Cura settings pasted below:





Edited by polygonfuture
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    Posted · UM3 Heat Creep on Filament causing seizing


    it seems your print head cooling fan (the one inside the flap) is not working properly.

    This fan should always run if the temparature of a printcore is above 60°C.

    Check the fan for debries and clean it (see here: https://support.makerbot.com/s/article/1667337928504 and here: https://support.makerbot.com/s/article/1667411590139)

    If the fan is clean and does'nt run at hot printcore, check the cabling and/or replace it.


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    Posted (edited) · UM3 Heat Creep on Filament causing seizing

    Thanks Enimga_M4.

    Reached out to local North American support (Thanks Erin at FBRC8.com!)

    Turns out I had the fan backwards. 

    Two weeks ago had a print flood the printhead and lost an AA core.  When reassembling looks like I flipped it by mistake.
    Air is now blowing onto the printhead vs away from. 

    Will test but this should fix my problem.

    Edited by polygonfuture
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