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[Mill] SOLVED Replaced Mill Table. Really bad backlash/slop now.

Discussion in 'CNC IN THE HOME SHOP' started by countryguy, Apr 20, 2017.

  1. countryguy

    countryguy United States Active User Active Member

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    On the thread 1 or 2 below I cover taking the Table off the Supermax YMC-30 Checking and repairing a few minor things. The table had developed .005 in X backlash over about a years time.

    After putting the table back on, I seem to have this horrible 3/4 turn before the table moves. Everything went back on the same way. I'm sure it's something simple, but I have done a disassy/Reassy 2x now, and I am stumped.

    I've loosened the gibs way up.. moved the table around... I just cannot seem to figure out where the sudden slop came from.

    On the far end, (non-motor) side of X, if you spin the knob CCW, I notice the wheel knob actually spins out 1/16th or so.(gap).then the table moves right Then you turn the knob back in till it stops and then the table moves. Maybe I need to pull that side apart as well?


    Thanks for any tips. Will get a video up if I run out of thoughts, ideas, etc.
     
  2. JimDawson

    JimDawson Global Moderator Staff Member Director

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    I'll bet you are missing a spacer between the nut and the bearing on the motor side. ;)
     
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  3. countryguy

    countryguy United States Active User Active Member

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    Still no clue but I keep learning... I cannot see anything I am missing yet. The two angular contact precision ball-screw bearings are a 'duplex' setup.
    Duplexed Bearings like these come in DB (back to back) and DF (face to face)... This guide taught me a lot.
    http://www.tristate-bearing.com/pdf/Barden/Bearings/barden_mro_catalog.pdf
    • Duplexed bearings are made by relieving selected faces of inner and outer rings by an amount called the preload offset. When the bearings are clamped into position, the offset faces are brought together, introducing a preload into the bearing system.
    • Bearings are mounted with marked faces or full shoulder side of outer rings together.
    So I need to yank it all for the 4th time, and insure the bearings are put back in properly. I cannot see any part I missed or was missing on the print.
    These systems are amazing when setup correctly.
     
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  4. TomS

    TomS Active User H-M Supporter-Premium

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    I experienced the same problem with my mill. Here's the link to my thread (http://www.hobby-machinist.com/threads/chasing-backlash.55182/). No matter what I did I still had backlash in X and Y. I did discover that running a warm up routine had an impact on backlash but didn't reduce it to zero. Over time backlash has increased, again, to an unacceptable level. Not sure if it's electronics related. My BoB is a Chinese cheapo. So I've bought a PMDX-126 BoB and a Warp9 ESS. We'll see what happens next.

    Tom S.
     
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  5. scwhite

    scwhite United States Active Member Active Member

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    Is this a ball screw and ball nut
    If it is you could have lost one ball out of the nut
     
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  6. countryguy

    countryguy United States Active User Active Member

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    :congratulate::encourage: Where the Dancing Bananna!!!! Dang, Love that guy. SUCCESS. Turns like a dream! Cannot feel any lash any longer...
    smooth, balanced, joy rotation. I'm really happy I took on the table off. The re-assy issue was related to those thrust bearings and installing them the proper way....
    • Bearings are mounted with marked faces or full shoulder side of outer rings together.

    :teacher:

    countryguy.. :cowboy:
     
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  7. countryguy

    countryguy United States Active User Active Member

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    Two Bearings (duplexed) are used for the X and Y ball Screw support on the Motor end. Depending on the bearing types, you have to match faces or backs for the preload to work correctly. The two bearings are bolted down w/ a small cover to set the preload correctly. Having 1 (or both?) these turned the wrong way caused something really odd to take place. Easy fix this time... lucky me!


    upload_2017-4-21_12-18-49.png
     

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