Excessive Stringing Lite-6

Discussion in 'E3D-v6 and Lite6' started by Jim Vogel, Nov 19, 2015.

  1. Jim Vogel

    Jim Vogel Member

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    I'm switching from the direct drive setup on a prusa i3 to a bowden one with a lite-6 at its heart. Originally it was a stepstruder mk7 based design. I have switched to an airtripper, mk8 drive gear, and a larger stepper motor 96oz/in. Nothing else in the printer or slicer has really changed in terms of speed except retraction.

    The only difference from the stock v6 i have added is ceramic fiber insulation around the heater block. Maybe this was a bad idea? I did it so i could maintain steady temps and have a cooling fan blowing nearby. Temperatures are super stable with or without the fan on, never tried without isulation.

    I have switched to firmware retraction so I can modify it on the fly and have tried ranges from 1.5mm 20mm/s to 7mm 80mm/s. I have also adjusted temperatures all the way down to 175 degrees (The pla im using is rated for 220-190) where under extrusion starts happening. The motor is not skipping on retraction. I have also done my best to calibrate from over extrusion.

    No matter what I do the nozzle seems to ooze any time it dwells or needs to stop extruding. Noticeable blobs at the end of a perimeter or at edges of infill (where direction changes significantly).

    My next thoughts are to shorten the bowden length (its about ~650mm at the moment) and/or remove the insulation. If/when I mount the extruder to the printer I could probably get the bowden tube to about 150mm.

    Part pictures below:

    Hotend pictures taken on my phone are too big to uploaded to postimg

    Extruder 1 http://postimg.org/image/mnevg9ih1/
    Extruder 2 http://postimg.org/image/ur5z760lf/

    Note: the dribble hanging off is shows up after even a 2mm retract at the end of a print :(.

    Can anyone give me some other suggestions? Been googling around awhile looking for possibilities, this stringing is driving me nuts.


    Picture 1.jpg Picture 2.jpg
     
  2. Jim Vogel

    Jim Vogel Member

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    for the TLDR;

    If you have lots of stringing, Measure how deep your ptfe tube is in and make sure it seats all the way to the nozzle!

    So I just took the whole thing apart and checked what was going on. I am posting this in case anyone else runs into the issue. When I opened the lite-6 there was melted plastic in between where the ptfe liner should have been and the nozzle. Since the ptfe liner was not fully seated (about 1.5mm back) There was a larger chamber for melted plastic to pool and add pressure. After getting the PLA out... I felt inside the lite 6. There is a noticable "lip" i can feel on the inside edge about 1.5mm up inside the heatsink. Its very slight but enough to catch the PTFE. My fix was to stick my ptfe in a pencil sharpener and shave off just a hair of the square cut edge. Now when I push the tube in.. I can still feel it catch the lip but then seats correctly.
     
  3. triplanedave

    triplanedave Member

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    And, how is the stringing now that you adjusted the PTFE tubing? (BTW, I agree, tapering the end of the PTFE that sits into the hotend is a requirement for a good seating and prevention of that small melt cavity).
     
  4. elmuchacho

    elmuchacho Member

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