B/S sizing was Re: Ball screws

Tbrooking,

The primary items used to select leadscrew/ballscrew diameter are:

1)Length between support(s) of the screw.

2)Type of support, including whether both ends are supported or not.
In previous posts I have detailed the three types of end support
common to these screws. They are referred to as simple, fixed, and
rigid. They are used in many differing combinations. See the CCED
group archive online, or look at any mfr. literature for details.

3)Speed of screw rotation.

4)Weight of the load upon the screw, especially if high accel/decel
is needed; OR if the screw is at times supporting the load (called
column or compression load, and typical in Z axis milling apps).

Most mfrs. of screws will offer either software to determine
appropriate screw size; or will publish a "nomograph" for the same
purpose. (this is the name for that funny graph that you lay a ruler
or other straight line across the labeled points corresponding to
your needs, and read the "rest" of the details by looking where the
line crosses the "other" parts of the graph)

Hope this helps.

Ballendo

P.S. You will want to determine whether the TIME and effort/money
spent on the encoding scheme will cost as much as starting with
better screws and deleting the "fancy" feedback method. And, as
always, whether you will really NEED (or get) TRUE .001 performance
from this machine.

--- In CAD_CAM_EDM_DRO@y..., tbrooking@s... wrote:
> Allan:
<snip>The screw sizes on your drawing show a screw with a 3/4"
>diameter. What criteria made you come to select that size of screw?

>On my machine I would like to use some form of feedback loop that is
>relative to the table position and not the screw angle. I was
>thinking that way I could lower the cost of the screws by purchasing
>a rolled screw versus a ground screw.
<snip>Do <you> think that using a simple method of encoding table
>position like the ones above along with less expensive ball screws
>and still be able to maintain good accuracy (0.001 tol. or better)
>is practical?