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Z Axis Artifacts - Known Issues and Fixes

Discussion in 'Mods and Upgrades' started by Ziggy, Jun 1, 2014.

  1. tesseract

    tesseract Moderator
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    that could be an issue as when straight they would be symetrical but not so much when both are off
     
  2. Galaxius

    Galaxius Well-Known Member

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    Thats what I thought. Guess I'll be contacting the supplier.
     
  3. tesseract

    tesseract Moderator
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    just make sure they don't issues specs on the part before you buy or if they do that this exceeds them
     
  4. Ziggy

    Ziggy Moderator
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    You might get away with it but IMO I would not spend time and effort putting in rods I was not 100% happy with. All it takes is a few 100ths of a millimeter variation on the Z and print quality suffers.

    Any chance you could straighten them with some gentle persuasion?
     
  5. Ziggy

    Ziggy Moderator
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    Great result.

    The Z Stepper power disable is definitely a cause of variation on the Z (up to 8 uSteps lower or higher each layer raise 8/2267.72 = +/- 0.00353 mm for 5/16 rods) . I really would suggest you try it.

    Can always reverse the change easily if you are not convinced.
     
  6. Galaxius

    Galaxius Well-Known Member

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    I've contacted the supplier so hopefully I hear back soon. I could spend hours trying to correct the bow and get no where or make it worse. They weren't too expensive but they should have been straight. I'll wait to see what they say. I'm looking forward to doing the upgrade so it's annoying. Thanks Z.
     
  7. scotta

    scotta Active Member

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    Ziggy, thanks for your effort and very systematic approach to addressing this issue and helping us all improve our print quality.
     
  8. collin

    collin New Member

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  9. tesseract

    tesseract Moderator
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    You may want to contact Jerry at Robo he may should be able to give you the information and if you ask nicely he may even sell one or two to you.
    I have never sources the coupler I got the 3-5mm ball bearing from the local bike shop about 03 cents each though if that helps
     
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I am going to toss this out here, food for thought only.
    I did not have the ribbing, not at all.
    I swapped from the 0.4 to the 0.6 nozzle, made the appropriate slicer/software changes and printed for a bit with that nozzle.
    When I looked at one of the taller prints I saw that I had a little of the ribbing. I rechecked all of the software settings in the event that I missed one, but all were good. Swapping back to the 0.4 nozzle (and resetting the software) has once again removed it. It was never horrid, but it was there.
     
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  11. Ziggy

    Ziggy Moderator
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    I assume you also printed at a different Z layer height with the 0.6 versus 0.4mm nozzle. Is that correct?
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I did not change it. I assumed it would still be able to use the same layer thickness,
     
  13. Ziggy

    Ziggy Moderator
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    In that case it points to an extrusion issue causing the Z artifacts (maybe filament spool being pulled by the extruder periodically or hobbed bolt ?).

    Of course it is also possible that a very, very slight Z Ribbing was there already but the different nozzle/filament has made it visible.
     
  14. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    It could be an extrusion issue. I have (in the past) fine tuned the extrusion rate and I did not touch that when I swapped nozzles.
     
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  15. tonycstech

    tonycstech Active Member

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    So if overheating is the only reason to adjust the board, can i just leave it as is since i have a cooling fan blowing at it all day ?
     
  16. polylac

    polylac New Member

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    Hi
    first thanks to ziggy for his great work

    While replacing my rods i realized that even M8 rods don't fit into the coupler (or at least mine ;))
    M8 x 1.25 have a diameter from 7.760 to 7.972
    M8 x 1 have a diameter from 7.794 to 7.974 (so this should be a bit better)
    But a bit of Sellotape or Scotch tape(I guess that's the name in english) solved the problem.

    The main thing i wanted to point out is that the problem is not so much the teflon tape, but the little screw that pushes against the rod. On mine this was tightened (needed to because otherwise it wouldn't fit) so i tightened this one too. But then the rod was really misaligned. (The rod itself is perfectly straight)
    Now with the Sellotape / scotch tape only its almost perfect (3mm at 300mm lengths, an I thing i bended the coupler because at first i thought this was the problem)

    Maybe a solution could be to print a small tube with a split, with outer diameter of 8mm and inner of 6mm (or 5.5 and then drill it properly) and use M6 threaded rods, one advantage only 1mm per turn.
    Maybe i try this once.
     
  17. scotta

    scotta Active Member

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    So I have done a few of the list of upgrades to remove the ribbing + some others

    Fix 2 - Making sure the threaded rod/nut stiction and friction is as low as possible. clean everything and use moly grease (would probably be better with a dry lube but did not have any, on my list to do)

    Fix 3 - Setting the motor shaft in the coupler so it does not slip

    Fix 4 - Stopping height variation due to the coupler geometry - essential. Added a bearing in each coupler

    Fix 5 - Seating the threaded rod properly centered in the coupler + replaced stock with M8 rods
    I also did a bed upgrade at the same time.
    A significant improvement to print quality as shown in the attached photo, latest print on the left.
    FullSizeRender.jpg
    To do;
    install some Z-rod sstabilizers
    Fix 1 - Firmware Z Disable configuration change

    Ziggy thanks for the detailed post and information
     
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  18. Ziggy

    Ziggy Moderator
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  19. tonycstech

    tonycstech Active Member

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    That site sucks. Cant see anything without registration.
    Plus, who needs to read entire poem when all it takes is replace the rods with metric once.

    Nice dog by the way.
     
  20. Ziggy

    Ziggy Moderator
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    Actually metric rods make very little difference. Main issue with Z Ribbing is minimising any Z height variation (ie in the couplers and slippage).

    The woofer is a Husky. Too smart just to be a dog.
     
    #40 Ziggy, Nov 23, 2014
    Last edited by a moderator: Nov 23, 2014
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