Ballscrew problems

[iregan]

Hi,
I'm having a problem with a ballscrew on my machine.
It was spitting bearings out so I tore it apart, cleaned it and replaced the bearings following the instructions online.
The ballscrew isn't spitting bearings out now and I can hear the clatter of the bearings in the return tubes, but its tough to turn. I lubricated it more, but still its tough. Any ideas??
Thanks.
Regan

[CRFultz]

Did you by chance miss one?
When I was reloading one I noticed that it would turn a couple of turns ok but then would get tight.
I discovered that I had one more hiding in the rag on the workbench, when I got it back in it ran smooth.
Just a possibility. I think the path for the balls needs to be full in order to function smoothly.
Chuck

[iregan]

Thanks!
I'll try some more, I actually have no idea how many the ballscrew had originally, most had spit out by the time I pulled it to repair. I left some room in because I wasn't sure if there wasn't supposed to be some space.
Regan

[jcc3inc]

Gentlemen:

On one of the sites I visit a similar problem was discussed; one user wanted to replace the balls and had problems. A respondent stated that he should carefully measure each ball as they are separated into full size and slightly smaller, -.0002 or so! Then re-insert the balls in the order large-small-large-small etc. The reason given for this was that the smaller bearings actually run backwards; they are used as spacers only, and contribute to the smoothness of operation in that the two adjacent balls do not scuff each other. Makes sense, doesn't it?

I have not confirmed this!

Regards,
Jack C.

[coherent]

just as a side note, make sure your screw & ball mounts are aligned and your axis is truely square. I've seen ball nuts fail when alignment was not perfect, which causes excess friction on the bearings on one side of the nut. It may very well be another problem, but alignment problems can definately cause the issues you mention including the initial "spitting balls".
-Marc

[iregan]

Thanks for the ideas.
The ballscrew was spitting bearings even out of the machine, when I repacked them it stopped spitting bearings out, but its binding somewhere. I still haven't put it back in the machine. I may end up pulling the ballscrew for the other axis(its identical) and checking it out.
Since I have never spent any time on the machine I'm wondering if they are even the right size ball bearings, maybe just a little too big.
I will pick up some slightly smaller bearings today or tomorrow and try them out as spacers, that sounds very plausable. Unfortunately, I can't get to the machine to pull the other screw for a few days.
Thanks
Regan