Hi
I have previously used the Nook pre-loaded ball nut on their rolled ballscrew but thought I might try using two of the normal ballnuts to remove the backlash. Is anybody able to help me with a design so that I retain at least on one of the threaded shoulders to attach a flange.
thanks

Hey Rod

I've been thinking the exact same thing.
Been searching the net for detailed drawing of the nut as I don't have one in my hand as you do.
I have some ideads but without the nut to look at it is a bit hard.

Remember seeing somewhere, someone selling plans to do this. $5 as I remember, but don't know where I saw it.

I'm sure it can't be too hard to do.

The other thing is you could probably quite easily load oversize balls as needed.
Don't think they would be hard to get.

Ordered my steppers :)

Greolt

Industrial Hobbies used to have this posted. They're redesigning the site, and Aaron promises all of the old content will go back up, but it may take a little time. Wavy washers (Belleville?) between the two nuts provide the preload.

Best,

BW

http://www.cnczone.com/forums/showthread.php?t=17009&page=1

I had notes how to preload two ballnuts together in the above thread, post #12.

Neatman

Hello. After several tries, I arrived at the "stiff bar" solution as you linked, Neatman. Rather than making a stiff bar of the exact length between the two nuts, I simply machined an eyelet on one of the ends so I can push the nuts apart and lock them down with the bar. This gives me control over how much preload I add and, IMHO, is a better solution that a spring/washer as it will not flex in either direction.

JR

Thanks for all the replies.

There seems to be a few ways of connecting the nuts and I like the idea of the adjustable fixed bar.

JR, so I am visualising what to do, do you have a photo?
No point in re-inventing the wheel if you have something that works.


Greg,
Good news about getting the steppers. Email me the details of what you got.

Hey Rod,

I went out and took this rough pic. You can see the two nuts, the support bar and the nut mounts. One of the mounts is attached to the X axis cross bridge on this gantry style machine. The other mount simply holds the preload nut, Nut2. Both supports are identical parts so the one for Nut2 protrudes above the nut. I guess a second bar on the backside would improve stiffness but it has worked fine as is.

The original design had one nut on each side of the gantry bridge and the nuts were tucked under the X axis beam. However, because my supplier sent me bent screws having the nuts apart as much made it bind a bit more than I liked. With the nuts closer together they can ride the slight bends without any noticeable effort on the motor.

JR

Hi JR
That is a better and easier than I had in my mind. Thanks for taking the time to explain it and post the picture.

:cheers:

What I was trying to explain was using the thread of the ballscrew itself to create the preload. If you solidly mount one ball nut, the second floating ballnut could be rotated into the fixed one with a lever and a spring (like a wrench with a constant torque applied). So, as the nuts wear in, the spring rotates the second nut a tiny bit, and eliminates the backlash. There would never be a need to adjust backlash, and the amount of preload is determined by the amount of torque you apply to the second nut. This is a trick normally used on anti-backlash leadscrews.

Neatman

That's a good idea. That's basically how I have mine minus the washer. In my case, I will have to readjust at some point as they wear in.

JR