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Thread: Tips for Adjusting Bearings on Z axis?

  1. #1
    Join Date
    Aug 2008
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    Default Tips for Adjusting Bearings on Z axis?

    Is there any documentation on how to go about this?

    About a month ago, I noticed a little side to side 'slop' in my Z axis. I loosened the 4 bolts on the outside of the channels, and used a flat wrench to tighten the bearings against the channels. When doing this ,I wasn't entirely sure which way I should be turning the bearings to get them snug. I turned the ones in one track in one direction, the ones in the other track in the other direction. (They appear to tighten when turned in either direction?). I adjusted things so that movement in the Z axis was fairly (too?) stiff.

    Today I ran into issues with driver/motor faults when plunging. I turned off the control box, unplugged the Z motor, and the Z axis was very stiff, more so than when I had adjusted it.

    Am I doing something wrong? Is there some rule of thumb in terms of how stiff the Z-axis should be? Is the design really meant to have no lubricant inside the channels?

    Thanks.

  2. #2
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    iBILD Solutions - Southern NJ
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    Default

    Nat,
    It sounds to me like you have the Z axis gear rack rammed against the pinion causing it to bind. Loosen up the tension or you will spread the Z axis towers apart and cause other problems. Take your time, check pinion to rack mesh (tighten as lightly as possible to get proper mesh), check Z axis level and adjust as needed - REMEMBERING that you can affect pinion to rack mesh while doing this. Take your time, observe what is going on & you'll be fine.

    -B

  3. #3
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    Default

    Nat - After you adjust the bearings on the Z axis, be sure to check that your Z is not plunging at an angle in the Y axis plane. Adjusting these bearings will affect this. I check mine by installing a test indicator in the collet. I then take a good quality machinist's square and stand it up on the table then zero that against the test indicator. Then manually jog your Z up or down and watch the dial face for any runout.

  4. #4
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    Thanks guys.

  5. #5
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    Default

    Nat...
    The adjustments are eccentrics similar to those on the bottom of the YZ car. I try to adjust all mine in the same direction to eliminate the problem Brad describes above. IF you go to snug clockwise on the right of the Z extrusion, go CCW on the left. Dont know if this really changes anything, but makes me feel better!

    Gary

  6. #6
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    Thanks Gary. I'm going to give it another go this weekend. I had to adjust it on the fly the other day, to get through the job, but need to go at it again under calmer conditions.

    No lubricant inside the channels?

  7. #7
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    Default

    Nat..
    You might want to pull off the Z motor to make sure that its not putting any pressure while you make the adjustments. Brady makes a good point above. As you do this work the Z up and down by hand to get a feel. You want things snug, with no play, but definately not binding. After you are happy with the Z thru its full range of motion, then set the motor in place and make its adjustments.

    I dont know if its recommended, but I use a lube in there. I see on the new machines there is a plastic "chip diverter" that may keep stuff out of the channel.
    Gary

  8. #8
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    Thanks Gary.

  9. #9
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    Nat...
    The documentation is here: http://www.shopbottools.com/documentation.htm

    (General, second one down)
    Gary

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