Re: [CAD_CAM_EDM_DRO] How does one adjust Ballscrews on a Bridgeport

Stephen Wille Padnos wrote:

>R Rogers wrote:
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>>Ballscrews are like that. They feel spongy when they have no backlash at all. I ran a manual machine with ballscrews and it was exactly like what you are describing. I dont know why they are that way. They feel much different than an acme leadscrew which feels very solid. But, with a servo or stepper belted to them they will hold perfect position. I can't explain it.
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>>Ron
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>Interesting - that's also the kind of information I was looking for.
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>I would have just concluded that, based on my experience with these two
>machines. My friend has a lot more experience using these machines,
>though - he has owned a Bridgeport or two for the last 10 years. He's
>also a mechanical engineer (he actually makes money with his machines,
>something I have yet to do :). I would just live with it, and wonder
>why circles don't look like circles under CNC control. His concern got
>me thinking about it, and that's where the trouble began.
>
>I'd be interested if anyone else either concurs or disagrees with the
>idea that "that's just the way it is".
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Because of the low friction, ballscrews may feel more "spongey", but if
you can measure
axial travel of the screws, then something IS wrong, it is NOT just
feel! I've adjusted
the fixed bearing set on my retrofit (not a Bridgeport drop-in
ballscrew, so comparison
on the exact mechanical details can't be made) until there is NO axial
movement
whatsoever. It DOES have a block which holds the outer races about 1/2"
apart.

Jon