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  1. #1
    3D Printer Noob
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    Apr 2020
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    problem with the re-placement PLA filament on CubePRO

    Hi everyone - original PLA prints fine, i tried three other but extruder knocks and prints with holes - or maybe it's a different problem ?? (but whenever I go back to the original one it's ok). Please help

  2. #2
    Super Moderator
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    I have very little trouble with 3rd party PLA. But I don't use exotic PLA like GITD or harder filaments. The Cubes have a fixed filament gap and therefore harder filaments are problematic. Tuning for these filaments is also harder as they typically require a little more heat. As a baseline, I use 3D Solutech Real White PLA in the Cube3 - not a difference worth noting although the material itself is very different in effects.

  3. #3
    3D Printer Noob
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    Thanks Tommy I will check a softer filament

  4. #4
    3D Printer Noob
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    I've been trying to use a spool of Kodak "PLA+" and am having similar difficulties under some circumstances.

    By my observations, it seems like the PLA has more friction inside the feed tubes than other filament types and the extruder feed motor doesn't have enough torque to pull it along. Could be the hardness/stiffness of the material or the surface or both I guess. I do know that if I help it along by applying light pressure on the filament it feeds fine. Also, on the occasions that it broke, as the remnant of the filament made its way through the feed tube, once the tube got about 1/2 empty there was no more skipping.

    It's surprising because that's a pretty hefty stepper motor they have there. I'd think it'd have way more torque than that. Maybe the drive circuit doesn't deliver enough current to it.

    I've tried increasing the temperature to the max rating on the filament package (240c). When it does the priming operating during loading there are no issues, it'll flow right along for as long as you let it go. It's when it's printing that I have difficulties. Could it be that when it's priming it's even hotter than 240c? I have ABS chips in all my spots so the printer is operating on that information when priming.

  5. #5
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    I have seen this with common PLA too. Restriction in the bowden tube is a real issue. I qualify bowden tubes by pushing a piece of bicycle spoke through it. Bike spokes should be 2mm diameter exactly.

    Harder filaments make the filament drive motors work harder considering there is no give to the gap in the driver gear. The squish of the filament is what causes the restriction in the bowden tube as the filament is wider. And with the friction in the Teflon tube (yes, oddly enough - PTFE is not as slick as one would think) causes the filament to thermally expand. Add a lot of retractions and you have the perfect storm. I have had a very hard time getting qualified bowden tubing for my specifications.

  6. #6
    3D Printer Noob
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    Mar 2021
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    Success!

    I made a temporary spool mount above the printer and fed the filament directly into the extruder, bypassing the Teflon tube entirely. Even then, it was having a hard time feeding the filament in (it would prime perfectly but when printing it would skip)

    So I took the extruder out of the machine and took it apart just to see if there was anything jammed inside. As I was putting it back together, I realized there is some adjustment (or play) in the assembly whereby you can adjust the gap between the feed and idle roller. I spread it apart as far as it would go and tested it by hand just to make sure it still had some bite on the filament (it did). I reassembled it and it's been printing perfectly with the overhead feed arrangement.

    The next print I will test it through the tubes and see what happens.

    But actually, I might decide to make a more permanent overhead mount and make a plexiglass box to house it. It pretty handy being able to just feed the filament right down into the extruder...

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  8. #7
    Regular 3D Printer
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    Sep 2018
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    This might come in handy for you. I made a simple jig to center the cog in the feed bracket before locking it down. There is a standoff in the way that comes off with a 5mm hex. You're welcome to it - https://drive.google.com/drive/folde...hH?usp=sharing

    It's a really snug fit when printed on cube3. Let me know if you need a little more clearance.

    CubePro Motor Centering Jig.png

  9. #8
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    Mar 2021
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    Thanks. It's actually been working well being set at the maximum gap. In addition to PLA, I've also printed successfully with "Flexfill 92A" which is a rubbery, flexible material and also colorFabb_HT which is marketed as an extra durable material. I've got a few other interesting materials to try, I'll post my results

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