HemeraSkipping; Filament wrapped around idler, twice

Discussion in 'Troubleshooting' started by sjlee001, Oct 20, 2020.

  1. sjlee001

    sjlee001 Member

    Joined:
    Sep 30, 2020
    Messages:
    4
    Likes Received:
    0
    Symptoms:
    • Extruder stops...extruding
    • Idler/drive skipping (idler lever jumps, tightening idler screw to within 25.4mm of death fixed it)
    • Stepper motor gear skipping (drive gears visible from the top are not moving but the stepper motor ticks furiously)
    • Filament wrapped around idler gear, twice!
    Filament: Hatchbox black PLA 1.75mm kept in Polybox Edition II with 1/2 metric ton of silica gel.

    Hardware:
    • Hemera coldend (filastruder)
    • E3D titanium heat break (filastruder)
    • uxcell Snowfan 40mm x 40mm x 28mm (Amazon)
      • i.e., mini turbine jet - took off a piece of my thumbnail and finger tip
      • Apparently can be used to cool smallish fusion reactors
      • It's a beast.
    • Maxiwatt 50W 24V heater (Amazon)
    • E3D 0.4mm nozzle (Amazon)
    • Ender 5 Plus (ebay), unenclosed.
    Software:
    • Cura
    • PrusaSlicer
    • Marlin 2.0.6
    Settings (in an exhaustive number of combinations):
    • Hotend: 185-210° C
    • Bed: 60-65°C
    • Speed: 10-80 mm/s
    • Cooling: 0-100%
    • Retraction: 0.0(off)-1.0mm, 20-35mm/s
    • Layer heights: 0.12-0.3mm
    (I can't seem to figure out how to post pictures....)

    Hmmm, what else to write? I've been having some of the same trouble other people seem to be having with their Hemera, maybe "heat creep"? It seems the filament near the drive hobbs/gears seems to blob up and jam the works.

    Photo 01&02: I just took it apart for the 1,000th time and found the filament had wrapped itself around the idler.
    Photo 03&04: To my surprise, when I shined my flashlight on the gears, there was another layer of filament wrapped around the idler!
    Photo 05: After removing the second layer of filament around the idler, low and behold this monstrous blob of which I had never seen before in my previous 999 disassemblies.
    Photo0 06: all the pieces I removed AFTER the first layer of filament. (I thought that was the only piece so I threw it in the trash along with 1,000,000 other little pieces. I should have kept it to neatly picture with the rest of it's brothers/sisters.)[​IMG]
    Photo 07: Picture of the first prototype. The next version uses a remote two-stage hybrid fan:120mm blower fed by an 80mm axial fan to a duct that diverts half the air to the heatsink and the other half to the nozzle to cool the part..

    Any solution to this besides the washer trick (didn't work for me with a ceramic washer) and mucking about with the settings?
    [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG]
     
    #1 sjlee001, Oct 20, 2020
    Last edited: Oct 20, 2020
  2. Marcus Mendenhall

    Marcus Mendenhall Active Member

    Joined:
    Mar 24, 2020
    Messages:
    31
    Likes Received:
    5
    The Hemera is not compatible with the standard heatbreaks. You have to use the Hemera-specific ones. This may be causing misfeeds.
     
  3. sjlee001

    sjlee001 Member

    Joined:
    Sep 30, 2020
    Messages:
    4
    Likes Received:
    0
    Yes, this is a Hemera-specific heat break. I have two titaniums and one steel.

    I've got a CAD model from grabcad so I'm tempted to run a thermal FEA model, "just to see."
     
  4. sjlee001

    sjlee001 Member

    Joined:
    Sep 30, 2020
    Messages:
    4
    Likes Received:
    0
    Sure enough, in the middle of printing a raft, it jammed up again with a medium sized blob.

    I used the default Cura setting for 0.2mm layer thickness. The stock extruder/hotend printed out the calibration cube quite well.

    [​IMG]
    [​IMG]
    [​IMG]

    The frustrating part is that the blob makes it EXTREMELY difficult to remove the drive gear assembly.
     
  5. Marcus Mendenhall

    Marcus Mendenhall Active Member

    Joined:
    Mar 24, 2020
    Messages:
    31
    Likes Received:
    5
    OK, I didn't know they had the titanium Hemera one available yet. Your idea of doing an FEA model may be overkill, but a good airflow model might not be a bad idea. I suspect your modified cooling system just isn't keeping the heatsink cool. Given the constrained filament path in the Hemera, it should be nearly impossible to have the filament wrap around things. I have printed about 20 kg of filament (making PPE and hand prosthetics) since I got my Hemera, and only had one clog. That was from doing a bad filament change (too low temperature) which broke a piece of filament off inside. It did leave a blob, which did make getting the thing apart a bit difficult. It was a small blob, so the first time I (partially) disassembled it, I didn't see it, so I had to try a second time with a full disassembly.
     
    sjlee001 likes this.
  6. sjlee001

    sjlee001 Member

    Joined:
    Sep 30, 2020
    Messages:
    4
    Likes Received:
    0
    Hi Marcus, thanks for you help! I was starting to go crazy(er?).

    You got me to start, ahem, thinking and I watched the filament on a new print (10mm/s first layer -> like watching paint dry) for ~15 minutes until it clogged...and I found the problem!

    The stock E5P had the Bowden tube zip tied to the split-plastic wire conduit and I re-used that setup from my filament box.

    The problem was due to the Bowden tube getting bent to an almost-90-degree angle at certain points along the build plate because the conduit would "flop" over. The flop point wasn't consistent, which is part of the reason I went crazy.

    I separated the Bowden tube and low and behold, no jamming blobs! I feel stupid, which is the norm for me....

    Thanks again!
     

Share This Page