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Y Axis blues

Discussion in 'Troubleshooting' started by mark tomlinson, Nov 10, 2013.

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  1. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    (Let me start by saying that the Y axis belt seems tight enough.)

    When starting up, it often will not travel all the way to activate the Y axis limit switch (which then causes it to want to jump--it makes grinding noises as it spins against the belt since it is not able to move further and the motors want to keep driving it to the limit).

    It is a physical binding. You can't force it further.
    Tearing the bed off and reassembling will solve it for a number of prints.

    However it gets back to the same situation. Homing it will cause it to try and go to the limit, but it just can't... The belt itself seems to be fine, there is nothing obvious wrong with it.

    Since all I can see that changes when I disassemble the bed is the that the Y axis belt is removed and replaced...what is the possible culprit? Y Axis belt too tight? Too loose? I can't for the life of me see (visually) what is causing it to bind and not travel that last bit. It seems to be correct tensioned, and once it starts printing everything is ducky. There is no aberrations on the X or Y axis.

    (I also lubed the bearings/sliders the last time it was torn down and they move smooth and clean).
     
    #1 mark tomlinson, Nov 10, 2013
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    OK, I found it and fixed it.

    The attached picture (sorry blurry) was the point of issue. The Sprocket that drives the Y belt (on right) was too low. It was then pulling the belt down when it moved towards the extremes of the Y axis travel. This was binding the belt on the pulleys. I raised the drive sprocket on the shaft (to where it is in the blurry picture) maybe an 1/8 of an inch higher. This keeps the belt moving smoothly and does not bind on the pulleys.

    This is now also loctited.

    As a side note I noticed that the sliders were not free to travel 100% both directions. There amount of travel was slightly different (for example one would go say 7.5 inches beyond the rail and the other only 6.5). I adjusted those (and re-lubed them) while I was there.
     

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    #2 mark tomlinson, Nov 10, 2013
  3. 1d1

    1d1 Active Member

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    Try to find what is preventing the bed from reaching the stop switch. When it does it next time, manually hit the switch to shut off the grinding, then carefully test bed movements. Look and see if the belt is at the end of its travel before it activates the switch. Make sure the ribbed side of the belt is facing the ribbed motor gear. It sounds more like a mechanical problem than software. The final thought I have is that the belt is not tight enough. It works for several prints, then is suddenly ineffective which means there is slippage somehow along the way...
    Good luck!
     
    #3 1d1, Nov 10, 2013
  4. 1d1

    1d1 Active Member

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    OK! Between the time I posted and read your previous post, you solved it. Nice piece of troubleshooting, Mark.
     
    #4 1d1, Nov 10, 2013
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Thanks, you were on the same track I was thinking when I found it.
    I had to watch the belt crawl up and down the race of the pulley to catch the problem in action.
     
    #5 mark tomlinson, Nov 10, 2013
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