Bowden tube pullback, and debris in the hotend

Discussion in 'General' started by Paul Winter, May 7, 2017.

  1. Paul Winter

    Paul Winter Well-Known Member

    Jun 11, 2016
    Likes Received:
    This is a first for me, but I'm guessing others may have had this, and have some way of dealing with it.
    I'm trying to sort out issues with one of my two E3D V6 hotends, and a possible problem with some nozzles - there may be a relationship here, and the problems may be feeding off each other.

    The nozzles appear to be rather fine, maybe causing hotend choking, and extruder clicking.
    The Hotend assembly is a Bowden setup.
    As part of trying to clear jams, and clean everything up, and generally just keep it all working, I have released the Bowden tube clips on the top of the heatsink to release the tube and pull it, and the jammed filament back out of the hotend.

    Now these Bowden tube clips have some wicked sharp teeth that grip the tube, and every time the tube is pulled out, even if you are really careful in making sure the teeth are retracted, some of the PTFE is shaved from the outside of the tube and left in the hotend/heatsink, ready to be pushed further into the nozzle once the tube and filament are re-inserted.

    _NM_0414.jpg _NM_0418.jpg _NM_0421.jpg _NM_0421-2.jpg

    Which on a fine nozzle contributes to jamming, leading to the whole cycle starting again.

    Does anyone have a technique or method for checking for, and removing this debris?
    Has anyone noticed a cold-pull working well here.

    I'm starting to think a routine cold-pull after a Bowden tube replacement/reinsertion might be worth doing as a matter of course.
    That, or some kind of sticky tool dropped into the heatsink when cool to fish any debris out. Something like a length of filament sprayed with 3M Spray-mount.

    Ignore the 3DBenchy, it was only there to prop the heatsink up at the right angle to get a look down.
    #1 Paul Winter, May 7, 2017
    Last edited: May 8, 2017
  2. mike01hu

    mike01hu Well-Known Member

    Apr 22, 2014
    Likes Received:
    Hi again! PTFE shavings will be very unwelcome in the nozzle and you are right to be concerned. With the Bowden setup it is preferable not to remove the PTFE tube other than for maintenance purposes and perform filament feed as usual via the extruder mechanism. Performing cold pulls are going to need you to remove the PTFE each time, so will not help with the shavings; cold pulls are mostly useful for blockages rather than general cleaning. A good tip is to include a long retraction after a print run to ensure the filament is clear of the hotend then, If you think it necessary, withdraw it, break off the end and re-insert; the retraction will drag bits from the tube and be stuck to the end. So much depends on the filament variety, with PLA being the worst for jams and some filled filaments being particularly "dirty", the polycarbonates seem to be best behaved but it's all subjective.

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