Re: Ballscrew Slop Question

John:

At 04:29 PM 2/13/01 +0000, you wrote:

>Hello All, I just installed ballscrews on my Bridgeport mill, in
>preparation for a CNC conversion. They were purchased from Hi-Win
>Industries. After installation, I noticed that there is about .002-
>.003 slop in either direction on the X axis. (the Y seems OK) I have
>been told that my bearings that are in the left side end cap might be
>at fault.

I recently installed Rockford ball screws on my Bridgeport size mill. I
have some .002 backlash in the Y. I had about this in the X but worked
with the alignment which eliminated it. I convinced myself that if the
nuts and bearings are in very good alignment the backlash was much better
or was eliminated. I still think this but don't really know why it would be.

I need to build new bearing blocks for Y and the right end of X to mount
stepper motors. I figured I'd take the time to align everything when these
are in place but not expend the effort until then. So, I can't confirm
this yet. But, you might spend some time aligning stuff and see if it helps.

This after adjusting the bearing "pre-load". The outer race needs to be
held to the housing and the inner race held to the lead screw without
play. If you look carefully at the bearing blocks or a drawing of this
it'll become obvious how the bearings are held. I suspect the bearings are
OK and I'd do quite a bit of fiddling before I spent the $ for new ones.

Please let me know if alignment gives you any gains in backlash.

I for one are interested in reading and seeing how you are putting together
the CNC portion. Please keep us up to date. Thanks.

P.S. If you do any manual machining watch yourself. I've been smart (or
lucky) enough to lock axes I don't want to move. But have broken a couple
of tools because my hand is calibrated for the acme screws and tends to put
too much torque into the handles attached to ball screws. Much smoother
motion though. :-)

Hugh Currin
Klamath Falls, OR