Re: [CAD_CAM_EDM_DRO] Does this make sense? was Re: Bent Nookballscrews ?????

Kim Lux wrote:

>This discussion might seem trivial and pedantic to you, but to those of
>us retrofitting/ building machines, these are important details and
>getting to the bottom of the physics is a very important to high
>performance machine operation.
>
>BTW: our machines are real and operational, used in a production
>environment, not some dream of an "ivy league engineer fired up on
>Expresso".
>
>
>

Hopefully a last word on this subject. I firmly believe that a fixed
preload is best, when you have a precision ballscrew with very little
pitch variation.

But, a number of people are using "power transmission grade" ballscrews
(with bends, bows or even KINKS in them) and 2 separate nuts to make
a homemade anti-backlash nut system. I think you HAVE to have compliance
in these, especially if "tight spots" are discovered in the travel.
You don't want a bunch of screen-door springs, you need something with a
real high spring rate, like thick Bellville washers or something like that.
If the pitch variation is so slight that you can tolerate the backlash in
some areas by setting the fixed preload to just not bind on the tightest
part, that is best.

But, I am totally convinced that putting a heavy preload force between two
ball nuts by some spring-like mechanism will not cause a torque load
on the screw of the same magnitude as delivering that same force to
an external axial load. If Mr. Lux would care to drop by my shop, I
am pretty sure I could throw together a demonstration of this in a couple
of minutes that he would be absolutely unable to refute.

Jon