Re: Any simple way to map ballscrews?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "vrsculptor" <vrsculptor@...>
wrote:

>
> Mach3 (and I'm pretty sure EMC) allows you to enter a leadscrew
> compensation table to correct for errors in the leadscrew pitch. Does
> anyone have any sugestions on how to measure the error other than
> using a dial indicator in the spindle, a block on the table and inch
> worming down the length of the table. I'm looking at using rolled
> ballscrews that can vary as much as .007 a foot.
>
> Roger
>

Others have mentioned how to measure, but if you want to correct for
the error, you can mount your nut so there is zero backlash, but the
nut can rotate in it's mount.

have an arm extend from the nut to a parallel runner. moving that arm
up or down would alter the locaton of the table as a super fine
adjustment. then all you need to do is grind the surface of that
runner so the arm rides on it, compensating as it goes.

I wish I could claim the idea as origional, but Les Watts did that and
had (has?) pictures on his web site.

Assuming a large screw, and a pitch of 1/2" inch, one revolution would
be 0.5" a quarter rev would be 0.125", and an eight rev would be
0.0625" it would be within the rhealm of possibility to correct for
that much over the whole of the axis.

Dave