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  1. #1
    Member
    Join Date
    Feb 2020
    Posts
    7

    DIY Preload on a ballscrew

    Greetings.

    I'm the owner of some very cheap chinese C7 (so they say) rolled ballscrew. Diameter 20mm/pitch 5mm.
    Obviously backlash is present and in a reasonable amount for the price but yet too big for my purpose. I was thinking about putting a double ballnut without replacing the screw but it is hard to find dealers that sell only the nut and also I'm not sure if I want to spend money on upgrading something that is not good in the first place (accuracy of the pitch isn't great too).
    So I was wondering if it is possible to just replace manually the balls inside the nut and replace them with slightly bigger ones so to give preload to the screw.
    Did someone ever tried to do this? Any suggestion on how much each ball bearing should be bigger (I have plenty of torque with the motors and I don't care too much about the life of the ballscrew)?

    Thanks.

  2. #2

    Join Date
    Apr 2020
    Posts
    17

    Re: DIY Preload on a ballscrew

    Hi Stefano.
    I am currently working on improving the chinese clone Hgr and ballscrews, and can tell their sizes vary quite a lot, so it is trial and error.
    I just finished my hgr 20, and had to use 5/32" in -10 to -2um steps, and as there are 132 balls in each car it is a litle time consuming, but came out very well.
    Now I am working on 1605 ballscrews, and plan to work up in sizes so 2005 will be next, but it takes a long time to get the right size balls, and they tend to be quite expensive in the g10 or g16 I buy, but still very cheap compared to the real ones, even hiwin.
    Later I can make a thread showing how to reball and what sizes to use, but to answer your question, first measure all the balls in the screw find the biggest size and reload with a grade 10-16 of that size. if you still have play, go 2um (0.002mm) up in size, but be aware that more preload is more wear, so proceed with caution.

    Good luck, Mike.

  3. #3
    Member
    Join Date
    Feb 2020
    Posts
    7

    Re: DIY Preload on a ballscrew

    Hi Mike,

    Thanks for the answer. Hope to see your thread soon.

    Good luck with your project.

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