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X carriage bearings

Discussion in 'General Questions' started by Wesley Knapp, Jun 10, 2020.

  1. Wesley Knapp

    Wesley Knapp Active Member

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    Are there 2 LM8UU bearings for each rod? I want to order some new rods and bearings but don't want to take the thing apart until I have the new rods & bearings.

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  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yes, there is one on each side of the carriage for each rod.
    [assuming I understand what you are asking]

    If you look at this model you can see where a bearing goes on both sides for the rods

    https://www.thingiverse.com/thing:647798
     
  3. Wesley Knapp

    Wesley Knapp Active Member

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    I understand where they go, just didn't know if there were two or if one using LM8LUU.

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  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I have only ever used the direct replacements -- LM8UU and not the LM8LUU however I can't see where that would let you get away with only one bearing so I'd still go with two. You need to support both sides of the chassis across the rods.
     
  5. Wesley Knapp

    Wesley Knapp Active Member

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    I was of the understanding that the Long bearing was the length of 2 of the LM8UUs

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  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    They are, but the two you need in that chassis are on opposite sides of the carriage -- not immediately adjacent to each other :)

    Each rod needs one on each side of that carriage frame for a total of 4 LM8UU

    edit: Actually I am not sure how much space is between the two bearings, but looking at the plate I do not think you would be able to substitute those.
     
    #6 mark tomlinson, Jun 11, 2020
    Last edited: Jun 11, 2020
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    If you were willing to let them stick out of the side of the frame you could probably use those and sacrifice a bit of x travel.
    However I am not seeing any benefit from that.

    I guess I would need to actually get my hands on them and try it to see if it is workable. I'd suggest just use the standard ones...
     
  8. Wesley Knapp

    Wesley Knapp Active Member

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    So it turns out that the Long bearing is exactly the length of 2 regular LM8UU bearings AND the carriage is exactly the same width.
    I have friend who is a machinist for a bearing manufacturer (McGills) and he says that the longer bearing is the better way to go because when you use multiple linear bearings if they aren't perfectly aligned/situated with each other, even a fraction of a degree difference will cause uneven wear or binding on the bearing and rod. This made perfect sense, even more so with the bearings being pressed into plastic.

    So tomorrow will see the replacement of the original rods (which are scored) and bearings (which are noisy). Looking forward to a more smooth and quiet printing experience

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  9. Wesley Knapp

    Wesley Knapp Active Member

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    Well As I was about to change out the LM8UU Y bearings, I can across some solid polymer Drylin "bearings" I ordered a while back for a garden project and figured what the heck. I've got it apart let's give them a shot."
    All I can say is WOW! Talk about quiet! Less play the the metal bearings and absolutely ZERO noise. I read to put a drop of PTFE lube in them, so I did. Lets see how they hold up. I think I'm going change out the X bearings with them as well when I receive the new rods on Tuesday.

    Now if I could only get rid of air noise from all the various fans I'd have no noise but stepper motors.

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  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yep -- drylin bearings are much quieter and generally smoother.
    They shouldn't wear any faster either. They just cost more than the generic LM8uu bearings do.
     
  11. Wesley Knapp

    Wesley Knapp Active Member

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  12. Wesley Knapp

    Wesley Knapp Active Member

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    All put back together with the polymer bearings and Robbie is printing perfectly and quieter than ever before. I'm impressed.

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