Setting up a new ball screw
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  1. #1
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    Default Setting up a new ball screw

    Hi guys,
    I've just run a high speed test program for the first time, - the Y axis screw was toast. sounded like rocks in a blender. not good.

    Anyway I've just fitted a new one (machine came with spares). I'm pretty sure i've got it lined up, but who knows...

    The new ballnut has what looks like a preload adjustment?
    Just want to check that this does not need touching by me, the clamping bolt for the nut has a plastic cap fitted and the bolt it loctited in already,guessing its factory set.

    There's a "-2" hand engraved on the nut as well, this obviously means something.

    Also - any tips / techniques for alignment would be appreciated.

    cheers

    rexroth-screw.jpg

  2. #2
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    The steps needed depend greatly on how the machine is designed and constructed. In the simplest of terms, you need to make sure that the screw is parallel to the ways in both horizontal and vertical planes. If the screw is supported in thrust bearings on both ends it may need to be tensioned. The mounting surface for the nut must be perpendicular to the screw centerline in both axes. The nut must be centered on the screw axis.

    Some machine builders establish all these at assembly by scraping/grinding/shimming/pinning the components. Others do it with shims only, and some seem to ignore all the above and just bolt everything together.

  3. #3
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    If the ways are worn you might want to leave the pins out of the bracket (s) and after the screw is moved to the closest end so you can read in to snug up the bolts and then ream the holes bigger or you may have to do a happy medium if the machine is worn low in the middle and not worn on the ends. As Van Biker aid use a L shaped gage to set on bed ways and mag base with .0001" indicator to line up top and side of the screw. If the screw is new then I would leave the backlash eliminator alone. Also be sure to tighten the screw up sothe end bracket thrust bearings are tight and when you are check backlash on moving part is zero.

    Also it would be a good time to check the gib clearance and remove and clean the way wipers.


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