Lead screws - made more accurate

Don Rogers wrote:

> Now, we are talking about lead screw accuracy, how do we get 0.001" per
> foot accuracy when the best lead screw we have is 0.006" per foot? And how
> did we come up with one that accurate when a machine that accurate didn't
> exist yet?

The machine doesn't have to be accurate, if you can calibrate
the machine, then apply corrections.

I believe Les Watts described on this list a year ago, a method
of 'mechanically' correcting a leadscrew (ballscrew or acme) by:

- determining the error (in fractions of a leadscrew-turn)
- machining the counter-correction into a linear cam
- a follower follows the spindle along the axis (along the cam)
and the cam torques the nut appropriately (which applies the correction).

Of course its far easier these days just to apply the correction
in software (conceivably even using hardware store all-thread and
getting reasonable accuracy).

I believe EMC/Linux can do this, I'm just waiting for the idea to catch
on in the other interpreter packages.

Doug Fortune
http://www.cncKITS.com





















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