Ball Screw preload
So, I'm buying some C7 ballscrews and I've never preloaded anything before.
I'm planning on using a torque wrench or a torque meter of some description. Now what I don't understand is how one deduces the newton meter or foot pounds of force to tighten the the nut appropriately, It requires about 2% of the CA figure which is 13800 newtons or 276 newtons. How do I take this newton figure and calculate the newton meter figure?
Any help would be greatly appreciated!
Thanks.
- David Nolan
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Re: Ball Screw preload
If you are using matched support Bearings then the Preload is already set, so you just torque up the retain nut to what torque is suitable for that thread Nut size nothing more to it, you can not change the Bearing Preload it is already set when you buy the matched Pair Bearing setsOriginally Posted by David_Nolan
You are only using a C7 Ballscrew so you don't have to over think this
Mactec54
Re: Ball Screw preload
Your right, but how do I know what is suitable for the thread nut size? Also there are other things i need to preload such as the fixed bearing and the trucks on the linear rails, my question also applies to them?
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Re: Ball Screw preload
There is no Preload that you can do or change with the Linear Bearings, when you buy them they have a Preload amount, depending on what Preload you chose to buy
You can find Nut Torque Specs on the web just search, every type of nut and thread has a Torque spec, there is nothing critical in your case so you can just do the nut up tight
It could be 45 ft-lbs to 400 ft-lbs depending on what diameter and thread pitch you have
You need more information as to what you have post some Photos
Mactec54
Re: Ball Screw preload
Yes more info needed.
If you get those BK blocks with standard bearings in you have to watch you don't tighten then too much. They can jam or heat up and fail.
I prefer to make my own mounts and use AC bearings instead. Much easier to work with and pretty forgiving.
Re: Ball Screw preload
So, These are the components I've been talking about.
https://www.tuli-shop.com/double-ball-nuts-dfu: Ballscrew
https://www.tuli-shop.com/trs-20-fn-h-z1 : Linear Truck
https://www.tuli-shop.com/bk12 : Fixed Support
So now my question is, why do they give you the preload if you can't change it or mess it up? I'm most worried about the Fixed AC bearing and the double ball nut as I have no idea if I need to be careful preloading them or how to go about preloading them properly.
Re: Ball Screw preload
The Linear Bearings say what the Preload is by what you posted, Linear guideway block, size 20, flanged, short, low profile, accuracy standard: H - high, light preload Z1 0,02C
Light Preload Z1 this is what you look for when buy these Linear Bearings, So as I said Nothing to set or change
The floating end of the Ballscrew Bearing is normally a regular Deep Grove Ball Bearing and would not have any Preload on this type of Bearing as they are not designed to have a Preload, can also be Preloaded with the correct Bearings in place, this puts tension on the Ballscrew
As for the Ballscrew support ( Fixed End ) Blocks and Bearing assembly's if they are of good quality, you can just lock the locking Nut up and the Preload will be set, again Nothing that you can change, as the Preload is already set
If they are cheap poor quality then you will have to find what works best for those Bearing Blocks as they will also have a lower quality Bearings with no determined Preload
When Angular Contact Bearings are made in matched pairs the Preload is set by the Manufacture, you can not change this in any way unless you are an experienced Bearing designer and have a high quality Surface Grinder, then you can use a regular Angular Contact Bearing and Grind them so you can give them a Preload
Mactec54
Re: Ball Screw preload
Okay thanks so much, that's simplified matters considerably.
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