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  1. #1

    Ender 3: PLA Jams Constantly

    A while ago, I took apart the printer due to a jam, and periodic mis-printing.

    The epoxy/ceramic around the nozzle, and the Teflon wrap was chipped away and no longer part of the print head.

    When removing the nylon tube, I didn't take note of the depth within the print head.Now I'm noticing the PLA gets jammed as shown in the image below, almost all of the time.

    The distance of the tube between the nozzle has been adjusted between a 1/4" and completely touching.The bed to nozzle adjustment is one sheet of paper at all four corners (checked twice). Also used feeler gauges.

    I've tried a higher bed to nozzle calibration thinking it was too tight .For whatever reason, the filament jams itself almost instantly, however when pre-heating the nozzle & bed, I can handfeed the PLA through the entire assembly and it exits with ease.

    Where do I begin troubleshooting? Is the printer no longer able to print without the white epoxy and Teflon wrap (heat sink)?

    Thank you.
    Attached Images Attached Images

  2. #2
    Engineer-in-Training
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    The tube which incidentally is made of PTFE tube should go right to the bottom of the heat sink, you may have to push it a bit further through the screw fitting at the top. being short will not help filament flow.

  3. #3
    Engineer-in-Training
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    Bed calibration is not likely to cause your problem! I don't know how thick you paper is but the paper I use is 0.08mm of 0.003" in old money. The normal slicer setting raises the nozzle 0.3mm for the first layer so there should be plenty of room for the plastic to flow.

    one thing I have found is that if the nozzle is much further away from the bed than that first layer adhesion is poor or none at all. I level in the normal way with a sheet of paper but check the ht of the nozzle over the bed with feelers gauge made of 0.002" and 0.003" ie 0.05 and 0.08mm steel shim stock. If the ht of the nozzle at the point of printing is outside these limits I adjust the whole bed up or down to correct.

  4. #4
    Thank you again.

    This morning I removed the nozzle and let the printer feed PLA for about 5 minutes. There was no jamming, or skipping at the feed gears.
    So I think the feeder motor and gear assembly is fine.

    Now I'm looking at the print feed speed. I don't recall changing any settings in the Gcode/Slice file, but it's possible the Cura Program might
    have reset, or changed some defaults, or maybe I clicked something by accident?

    More later...

  5. #5
    Student PlastiTech's Avatar
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    My guesses are that you either have a problem with heat creep, or the PTFE tube is not flat against the heater block, or the nozzle itself needs to be replaced.

    Heat creep occurs when heat from the heater block "creeps" up the PTFE tube and out of the "melt zone." This softens and may even melt the filament before it reaches the heater block and the nozzle, which are the only places where it's supposed to melt. Heat creep can be caused by the heatsink on the hotend not being cooled enough.

    If the PTFE tube is not pushed down flat against the heater block (or nozzle), or if the end of the PTFE tube has not been cut flat, then melted plastic can ooze out from the gap between the tube and the heater block, causing a jam.

    If all else fails, try replacing the nozzle.

    Over time, the PTFE tube may move upwards in the hotend, creating that naughty gap between the end of the tube and the heater block. There is a fix for this on Thingiverse. Here is the link : https://www.thingiverse.com/thing:4220059

  6. #6
    I think you may have nailed the issue.

    I'll try the mod and ensure the tube end is sitting flush, with a clean cut end.

    Maybe increasing the fan speed will also help cool the tube and prevent jamming in the final section of PTFE.

    Will let you all know if it works!

    Quote Originally Posted by PlastiTech View Post
    My guesses are that you either have a problem with heat creep, or the PTFE tube is not flat against the heater block, or the nozzle itself needs to be replaced.

    Heat creep occurs when heat from the heater block "creeps" up the PTFE tube and out of the "melt zone." This softens and may even melt the filament before it reaches the heater block and the nozzle, which are the only places where it's supposed to melt. Heat creep can be caused by the heatsink on the hotend not being cooled enough.

    If the PTFE tube is not pushed down flat against the heater block (or nozzle), or if the end of the PTFE tube has not been cut flat, then melted plastic can ooze out from the gap between the tube and the heater block, causing a jam.

    If all else fails, try replacing the nozzle.

    Over time, the PTFE tube may move upwards in the hotend, creating that naughty gap between the end of the tube and the heater block. There is a fix for this on Thingiverse. Here is the link : https://www.thingiverse.com/thing:4220059

  7. #7
    Seems like your theory is holding up.

    I turned down the nozzle temp. from 200 to 185, and maxed out the fan speed.

    The tube was cut back to remove the expanded portion and restore the "lubricated" characteristics of the PTFE material.

    So far we're 2 hours into the print. It's not perfect, but it's the first time making it this far without jamming.

    I'll have to buy a new tube, and invest in better fittings, as well as a new bed cover.

    Thank you all for the tips.

  8. #8
    Student PlastiTech's Avatar
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    You're welcome. I hope this completely solves the problem.

    185 on the nozzle is on the really low side, but if it works for you, great!

    Quote Originally Posted by YellowGTM View Post
    Seems like your theory is holding up.

    I turned down the nozzle temp. from 200 to 185, and maxed out the fan speed.

    The tube was cut back to remove the expanded portion and restore the "lubricated" characteristics of the PTFE material.

    So far we're 2 hours into the print. It's not perfect, but it's the first time making it this far without jamming.

    I'll have to buy a new tube, and invest in better fittings, as well as a new bed cover.

    Thank you all for the tips.

  9. #9
    Not much luck. I've out it aside , but need to order new parts from the feeder onward.

    New fittings , tube, nozzle, and bed cover at a minimum.

    I've also reviewed the Cura settings, but nothing appears to have changed.

  10. #10
    I had a simular issue with this filament here. I could not figure out why it kept jamming. I went back and actually read the reviews and it turned out it was the filament its self that was causing the problem. I put in something else and it worked fine. I would recommend reading the reviews ans see if anyone else has the same problem.

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