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Unanswered Y axis, lost steps?

Discussion in 'Troubleshooting' started by joea, Mar 24, 2020.

  1. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yes, the rods are press fit onto the ends. You will need to remove the Y belt as well, the belt tensioner can be loosened all the way and the belt removed.
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I don't know about the bronze bushings, I don't use them. The LM8UU works fine for me -- I have had to replace them once or twice over the years, but not often. Keep them lubed and they work pretty well. I imagine someone makes the bronze bushings, but I haven't looked into it. There are teflon IGUS bushings you can use too, but I have not tried them either.

    Some information here: https://reprap.org/forum/read.php?1,221763
    and here: https://toms3d.org/2016/06/07/should-you-be-using-igus-polymer-bushings/
     
    #22 mark tomlinson, Mar 25, 2020
    Last edited: Mar 25, 2020
  3. joea

    joea Member

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    So, the reason there are only 4 mounting screws/nuts on each side are . . . there are only 4 holes in the base..

    Now the question becomes, should I drill them, or leave it as is?
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Your call. I'd probably leave it although it is a bit odd.
     
  5. joea

    joea Member

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    I'll try to think that through. It is one of those early "kit" units I think, that had some upgrade over the years.

    Now that I have it apart, one of the bearings is quite rough, sliding solo.

    Also found the holes in the carriers and the bed, are quite tight for those screws, I had to thread them out of the carriers, one at a time. I think that is not good, so will address that before reassembly. A bit more clearance should allow for better "self alignment" on reassembly, I would think.
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Good ideas. If you add the other holes it will hold more firmly and shouldn't be a big deal.
     
  7. joea

    joea Member

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    Not to keep this going forever, but, seems to me, this sort of bearing should be lubricated internally, before assembly. Anything applied directly to the rods externally would pretty much get wiped off. Though when I have applied lube to the rods it seems to go somewhere. Don't see much of anything inside either of them though.
     
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    standard LM8UU bearings are lubricated during assembly and the better ones will not require more, but..,. they are a little pricier than the cheaper Chinese ones that can stand occasional lubrication.
     
  9. joea

    joea Member

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    Got a set of both steel and teflon IGUS bushings (I think, made in Germany, it says). The metal ones are not here yet, so I pre assembled the plastic ones.

    The are a few thousandth smaller in diameter, so were a bit loose in the holders. A wrap of scotch tape took care of that. That may not be the best solution, give that heat from the bed may have some effect.

    But they slide nicely and fit snugly, so we shall see.

    Waiting now for more hardware to fill the extra holes I drilled that were missing in the bed. Lots of restricted hours and travel advisories, so, everything is moving a bit slower and trying to consolidate trips. Not to mention a old fogey like me is strongly advised to stay at home where possible.
     
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  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I doubt the bed heat is even a factor, but good luck!
     
  11. joea

    joea Member

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    Still seems to be having a Y axis lockup about three hours into a print. I did find some mechanical bind with the new solid bearings at extreme + and - positions which might be due to some rod flex mid way, so readjusted with the bed at extreme ends.

    However it is getting a bit old as well as wasteful of filament to have a failure so near the end of a print. So, wondering if there is a test program that will exercise the printer in one of both directions for a settable time and/or distance?
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    why yes, there is...

    Just issue this GCode in the terminal -- line by line:

    G0 X 228.0 ;
    G0 X 0.0 ;
    G0 Y 254.0 ;
    G28 Y ;
    G0 Z 203.0 ;
    G28 Z ;
    G28 X ;
     
  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    That will not move the extruder, but it will go end to end on the other axis
     
  14. joea

    joea Member

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    Is there a way to make it loop, so the Y axis can "exercise" until stopped?
     
  15. joea

    joea Member

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    I just found something interesting. If I apply a modest amount of pressure on the bed, while it is moving under manual control within a few inches of either end, it will chatter, losing steps.

    Does not seem to happen nearer the middle of travel.

    Almost just the weight of my hand. is sufficient. There does not, by feel, seem to be a large difference in drag, with power off, but here is some increase at either end.

    I have changed stepper driver but never tried to adjust current.
     
  16. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Swap the bearings would be my first suggestion -- Yes, I know you switched to the Igus :)
    Make sure the Y axis belt is not binding on you...
    With the bed lifted move it back and forth full-stop, end to end.

    Then while doing that watch the belt as it passes around the center pulleys.

    Is it staying in the center or is it riding up and down? The latter can make it bind.
     
  17. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    If the bearing blocks are loose or cracked then pressing down on the rails while moving it can cause the same thing.
     

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