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Fighting Filament Jams

Discussion in 'Bulldog Extruder' started by CmdrKeen, Mar 20, 2014.

  1. CmdrKeen

    CmdrKeen New Member

    Feb 19, 2014
    Chicago, IL
    Hi all,

    For the last two weeks or so, I've been really, really pleased with the XL and my E3D. It's worked well and I've had no problems with either PLA or ABS until just recently.

    It seems that after I get, oh maybe an hour or so into a print, the XL starts to jam. What I'm seeing is that the filament is getting kinked up inside the XL. Sometimes if I'm near, I'll hear the "click" noise it makes as the hobbed pulley starts to slip against the filament (ABS doesn't click, just PLA). If I'm _really_ careful, I can usually get in and squeeze the idler assembly by hand and pull back on the filament, that will clear the jam and not interrupt the print.

    I checked the basics; Filament size is good - 1.6 - 1.9mm, and a nice round shape. Temp on the hot end is good, the nozzle appears to be clear, and I'm not "leaking" filament around the heater-block, feed tube/heat-sink assembly, or around the nozzle. I made sure the hobbed pulley is clean as well. I even disabled retraction settings in the slicers, thinking maybe that had something to do with it.

    The ONLY thing I can think of is that I've noticed the E3D is "loose" in the XL. I'm not sure what's going on there, but it appears that somehow the pseudo-groove-mount opening is somehow larger than it was before. I had some trouble getting the E3D out of the XL, and had to twist it as I unmounted it (i had to replace a bearing on my X-carriage). Now, what used to be a tight fit for my E3D and older J-heads is quite loose (loose enough to see the hot end move UP by a mm or so during a retraction). Not sure that's the culprit.. but I'm starting to lean that way.. (I wonder if I can just buy a replacement for the machined parts on the XL rather than a whole new one)

    I just pushed some "custom" firmware into my controller board to get the hot-end up to temp, and stuffed a thermistor down into the inlet for the hot end. I'm going to let that run overnight and collect the readings every 15 minutes or so to see if things are too warm at the hot end inlet side.. maybe the plastic is getting soft too soon...
    Anyway, I'd appreciate any suggestions or pointers! This just started happening in the last few days or so.

    Details on my setup are below.
    Prusa i2
    Bulldog XL extruder
    E3D Hotend (direct drive setup), .35mm nozzle
    Azteeg X3 controller, Repeiter v091r6 firmware
  2. chrisbob12

    chrisbob12 New Member

    May 13, 2014
    I'm still commissioning mine on a Prusa Mendel, and I've got reservations about how things are going with the filament path.

    • I've noticed that the filament can develop a 'set' from the hobbed wheel, which makes it hard to get through the brass bush just before the hot end starts. Although, see next...
    • I have to disassemble the extruder in order to start filament in it. If I try to run it in with the motor, it stops shortly after the hobbed wheel. This means taking the hot end off, and running filament through, so that there's some filament to position the hot end over. Since I haven't got it running continuously yet, I have to keep doing this :(
    Sometimes pushing on the filament helps, but that's not very satisfactory.

    My 3mm ABS is quite a snug fit at some points, so there's not a lot of room for manouvre. For info, I'm using the Merlin hot end with the 0.5mm nozzle, and I've run the hot end down from about 250C to 235C. The tensioner adjusting grub screws are a quarter turn backed off from fully screwed in. Maximum filament diameter is 3.06mm
  3. David

    David New Member

    Jan 29, 2013
    I tried the same thing.. lots of pressure ( screw both m6 to max then let off 1/2 turn.. ) and YES I think it deforms the filament and blocks it..

    I have noticed that the screw brass part below the hobbed gear can move up and down depending on the machining of the aluminium hotend.. ( i use the hexagon) and it does or doesnt attach with the two screws (m6 and M3? ) from the underside, IF that brass screw is too tight or too loose.does this make a gap in the flowpath.???
    I have another XL extruder and it secured the hot end just fine..first time.. the LITE model doesnt do it well at all.. seems to be 0.50mm difference between the two..
    I´m trying more options this afternoon :)
  4. Atreidae

    Atreidae New Member

    Mar 20, 2014
    I've found this can happen if you dont use the included fan to keep the top half of the hotend cold. The heat travels up.. increasing the size of the melt zone (the plug size lengthens) and causes friction to become to difficult for the extruder to overcome and it slips.

    One advantage of 3mm here is it doesnt kink up inside the extruder, I can usually back of the temprature a bit and pull it back out. But with 1.7mm it just turns into a mess inside the extruder.
  5. David

    David New Member

    Jan 29, 2013
    @Atreidae thanks for your reply.
    I run the fan at 100% ( on my XL Extruder ) from Repetier Host.

    I´ll be trying the LITE this afternoon :)
    So more soon.
  6. nephi jahn

    nephi jahn New Member

    Mar 16, 2015
    i having the same clicking issue. i can see the hobbled pulley twitching as it clicks. clicks for a couple of seconds than pushes the filament, print will go on for a little while and than will start clicking again.

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