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  1. #1
    Junior Member
    Join Date
    Aug 2016
    Posts
    39

    No preload into preload ?

    Hi guys ,

    I am upgrading my homebuilt cnc and have THK 2010 rolled ballscrews C7 class.
    On them i have BNT2010 2.6ZZ NUTS and those are not preloaded thus having as far as i understand 0.1mm axial clearence.
    Motion is provided by Nema34 closed loop steppers with LOADS of power..

    Is it possible just to change the balls with a number bigger balls to achieve lower clearance and thus eliminating that tiny backlash , or should i just live with it ?
    My cnc is 95 procent used for wood where high precicion is not needed , but then again never a bad thing to have high precicion.

    5 procent will be with aluminium and i have the option to calculate backlash into my control software.

    Just thinking what would be easy to do and not very costly

    Another thing i would like to ask here is greasing ? I have a couple of buddies that work with cnc mills every day and they NEVER had to grease their ballscrews not linear carriges ., i thought those would need regular greasing/oiling ????

    Best regards

    Kristjan

  2. #2
    Neuer Benutzer
    Join Date
    Jan 2013
    Posts
    263
    Quote Originally Posted by Kristjan1505 View Post
    Hi guys ,

    I am upgrading my homebuilt cnc and have THK 2010 rolled ballscrews C7 class.
    On them i have BNT2010 2.6ZZ NUTS and those are not preloaded thus having as far as i understand 0.1mm axial clearence.
    Motion is provided by Nema34 closed loop steppers with LOADS of power..

    Is it possible just to change the balls with a number bigger balls to achieve lower clearance and thus eliminating that tiny backlash , or should i just live with it ?
    My cnc is 95 procent used for wood where high precicion is not needed , but then again never a bad thing to have high precicion.

    5 procent will be with aluminium and i have the option to calculate backlash into my control software.

    Just thinking what would be easy to do and not very costly

    Another thing i would like to ask here is greasing ? I have a couple of buddies that work with cnc mills every day and they NEVER had to grease their ballscrews not linear carriges ., i thought those would need regular greasing/oiling ????

    Best regards

    Kristjan
    Indeed, there are ballscrew rebuild companies who can clean the ballscrew, then measure and fit "oversized balls" to reduce backlash. They will have many different ball sizes to selectively assemble. For example 8mm balls +0.010mm or other. They fit a full set of same size.

    Grease ballscrews every 2000 hours with recommend. Or some machines have lube systems. Greased for life ballscrews or linear rails don't really exist, over time they lose the grease.

  3. #3
    Junior Member
    Join Date
    Aug 2016
    Posts
    39

    Re: No preload into preload ?

    Thanks servtech for reply

  4. #4
    Member
    Join Date
    Jan 2005
    Posts
    15112

    Re: No preload into preload ?

    Quote Originally Posted by Kristjan1505 View Post
    Hi guys ,

    I am upgrading my homebuilt cnc and have THK 2010 rolled ballscrews C7 class.
    On them i have BNT2010 2.6ZZ NUTS and those are not preloaded thus having as far as i understand 0.1mm axial clearence.
    Motion is provided by Nema34 closed loop steppers with LOADS of power..

    Is it possible just to change the balls with a number bigger balls to achieve lower clearance and thus eliminating that tiny backlash , or should i just live with it ?
    My cnc is 95 procent used for wood where high precicion is not needed , but then again never a bad thing to have high precicion.

    5 procent will be with aluminium and i have the option to calculate backlash into my control software.

    Just thinking what would be easy to do and not very costly

    Another thing i would like to ask here is greasing ? I have a couple of buddies that work with cnc mills every day and they NEVER had to grease their ballscrews not linear carriges ., i thought those would need regular greasing/oiling ????

    Best regards

    Kristjan
    I can't tell if you have double Nuts on your Ballscrews if you have it is quite easy to create a preload, if not and the Ballscrews are new they will already have the max size Balls in them from the THK manufacturing, if they are used then you can most likely fit larger balls to help with the backlash.

    Your buddies CNC machines most likely are lubricated with oil, which is automatically done by the machine, Grease is used by some CNC machine manufacturers but mostly oil is used, for your Router don't over grease it as this will cause the dust to stick to the Linear Rails and Ballscrews then it gets inside and jams up the Bearing carriages and Ball Nuts.

    So, minimize the use of Grease, a lot use a dry Teflon lubricant, in place of Grease or use a combination of the (2) for CNC Routers, you will just have to see what works best for you, Linear Rails and Ballscrews need Lubrication, or they will have a short life without it.
    Mactec54

  5. #5
    Junior Member
    Join Date
    Aug 2016
    Posts
    39

    Re: No preload into preload ?

    They are old but brand new , never used. And nope ., not double nuts.

    I will look into the dry teflon thanks for advice man




    Quote Originally Posted by mactec54 View Post
    I can't tell if you have double Nuts on your Ballscrews if you have it is quite easy to create a preload, if not and the Ballscrews are new they will already have the max size Balls in them from the THK manufacturing, if they are used then you can most likely fit larger balls to help with the backlash.

    Your buddies CNC machines most likely are lubricated with oil, which is automatically done by the machine, Grease is used by some CNC machine manufacturers but mostly oil is used, for your Router don't over grease it as this will cause the dust to stick to the Linear Rails and Ballscrews then it gets inside and jams up the Bearing carriages and Ball Nuts.

    So, minimize the use of Grease, a lot use a dry Teflon lubricant, in place of Grease for CNC Routers, you will just have to see what works best for you, Leaner Rails and Ballscrews need Lubrication, or they will have a short life without it.

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