No preload into preload ?

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01-23-2023, 09:19 AM
Kristjan1505

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 :D

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
01-23-2023, 11:49 AM
servtech

Quote:

Originally Posted by Kristjan1505

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 :D

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.
01-23-2023, 01:57 PM
Kristjan1505

Re: No preload into preload ?

Thanks servtech for reply :)
01-23-2023, 03:04 PM
mactec54

Re: No preload into preload ?

Quote:

Originally Posted by Kristjan1505

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 :D

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.
01-23-2023, 03:10 PM
Kristjan1505

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

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.