V6 bulging filament out of nowhere

Discussion in 'E3D-v6 and Lite6' started by Andy Martin, Jan 20, 2018.

  1. Andy Martin

    Andy Martin Member

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    I'm a long-time v6 user but suddenly 80% through a reel of PETG filament I have started to experience filament "bulging" which causes extruder skipping about 20-30 min into a print.

    Here's a picture of what I pull out when this happens:

    filament-bulge.jpg

    You can see the dark area and subsequent bulge which I know is not normal. I have never had this type of issue with an E3D hotend before so I'm mystified why all of a sudden its happening.

    Everything is stock E3D 1.75 hotend, I have PTFE tube in place. It is cut flush at the top of the hotend. Using .5mm retraction so that's not the issue (which I read can cause this). Fan is stock E3D, I disabled my print bed fan as well and this still happens. Am I correct that the bulge is heat creep and that's where my jam is?

    Any recommendations on what to adjust?
     
  2. Andy Martin

    Andy Martin Member

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    More digging this morning led me to this great thread: https://forum.e3d-online.com/threads/jamming.136/page-6

    Seems that the top of the PTFE tube is likely not secure so that's what I'll be testing today. I've never paid attention to this in the past with my E3D's but we'll see if it helps. Also going to chamfer the inserted end was discussed in the following video:
     
  3. Andy Martin

    Andy Martin Member

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    A couple small prints later and I tried a 5hr print. Made it 4.5hrs in but then clogged same issue. Black mark and bulge jamming the ptfe tube. Any other ideas on how to troubleshoot this issue? Could it be the extruder gear getting super hot? I use a Bulldog Lite Extruder, direct-drive. Never had an issue but maybe I'll lower the current and try agin?
     
  4. Andy Martin

    Andy Martin Member

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    Still working on this issue and documenting my issue as I go... Retraction is not the issue as I use .5mm retraction length.
    Still trying to determine how else this could suddenly start happening.
     
  5. Andy Martin

    Andy Martin Member

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    I've spent considerable time reading this forum over the past 3 days and seems like the E3D isn't quite as bulletproof as it has been for me. That said its still the best hotend around.

    I am going to disassemble and re-assemble my hotend for the 3rd time in a week to try and mitigate this issue.

    1 Make sure all passageways are clean
    2. rinse off all old thermal compound and re-apply a fresh coat
    3. Ensure ptfe tube is pushed in 100% and the top is locked with a pin
    4. Try a different fan... no clues here but I have several e3d 30mm fans lying around from different builds so I might as well try a different one.

    Is there anything else I should do during re-assembly? Here's what my current end looks like, is it critical that the heatbreak is screwed 100% into the block? My current one is maybe not all the way in? As I understand it its better to screw it in all the way and then screw the nozzle up to it tightly? (hot tighten etc...) Could a damaged block be causing the heat creep? I think I have a backup as well.

    unnamed.jpg

    Last effort at getting some advice since E3D has not responded to my email or this thread, sadly.
     
  6. Spoon Unit

    Spoon Unit Well-Known Member

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    Looks to me like your heatbreak is in fine there. As you say, the heatbreak and nozzle are hot-tightened together to make the seal. The jam you describe looks very much like the result of a combination of retraction and heat-creep. I like the idea of mounting the bed sensor on the front of the fan like that but then, infront of that it looks like you have a grille of some sort in front of the fan? If so that's going to have two effects ... 1) make the fan noisier as the wind blows past the grille, and possibly 2) lower the volume of air being pushed onto the heatsink.

    Given that your failure only occurs after some time, I can understand the frustration and difficulty in immediately duplicating the issue.

    Things to try
    - a reasonably long print with no retraction
    - removal of grille infront of fan
    - replacement fan (if it's not fully functional)
    - increase of voltage to fan incase you've in some way dumbed it down to silence it

    Finally, it could just be detritus, but the shape of the nozzle looks a bit suspicious. Is it an original one? Is it old?

    All that said, you say your retraction is only 0.5mm, so it's hard to see how this could happen. Is the print quite slow at the point of failure due to a small layer and a slow moving head? If so, again that could point to the filament softening a little too high on the heatbreak.
     
  7. Andy Martin

    Andy Martin Member

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    Thank you so much for your thoughts, they are much appreciated! Print speeds are down to 30mm/s. The nozzle is an original but I will swap it out on this rebuild. I'll be trying another fan and will test without the grill (although its been on there for years without any issues).

    My biggest hope is that screwing the heatbreak further into the block is the culprit but I should know later today.

    Thanks Again!
     
  8. Ephemeris

    Ephemeris Well-Known Member

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    If I may add a heretical point. Do NOT reassemble using thermal compound. The point of the heat-break is to trap heat in the heater block. This serves two purposes:

    1) Increase efficiency by minimizing heat loss

    2) Makes the part farthest from the heater-block (i.e., the heatsink) cool enough that it can be mounted without melting or setting fire to whatever is holding the hot-end.

    Adding thermal grease just makes the heatsink and fan's job harder.

    Personally, I use red (yes RED) high-temperature Loctite to permanently attach the heat-break to the heat-sink. This saves me the grief of it occasionally unscrewing which I hate.

    UPDATE:
    Based on a conversation with Spoon Unit and Patrick Notton, I should correct myself. There is an additional design issue which is to keep the melt zone below the top of the heatbreak. You don't want a fast, long retraction pulling soft plastic up to where the PTFE tube starts. If that happens the filament can sometimes ooze into nooks and crannies such that, when it hardens, it's stuck in place causing a jam. I haven't seen this as a problem with my approach, but I don't use a bowden setup and I don't use filaments with low melting points.
     
    #8 Ephemeris, Jan 24, 2018
    Last edited: Jan 24, 2018
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  9. Spoon Unit

    Spoon Unit Well-Known Member

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    I have bent a heatsink, which puts me off the idea of locking it in, but I definitely understand why you did that. Amusingly (at least to me) when I originally assembled the BB I put thermal paste in the hot end to "improve' heat transfer from hotend to heatbreak. Bad idea. Ended up with a black mess I could never hope to clean and got a new heatblock and heatsink to fix.
     
  10. Andy Martin

    Andy Martin Member

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    I tore down the hotend, cleaned and rebuilt things. I screwed the heatbreak bottom threads into the heatblock until level, then added the nozzle. I did re-apply thermal paste in the manner e3d recommends but made sure to wipe the excess. Hot tightened all the parts... this time at 275 -a bit higher temp than I would normally use.

    In the end this rebuild fixed my issue. Back to perfect ever since.

    I would point out that e3d replied to my picture filled email with nothing useful. Surely, they could have spotted the heatbreak issue or recommended a rebuild to make sure everything was tight. Compared to the support a company like Lulzbot provides E3D doesn't seem to kill it in the support department but their products are still the best so...

    Hope this thread helps someone else - until next time.
     
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