Re: z axis drive question

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dave Fisher" <dave@d...>
wrote:

> I am in the process of building a Z axis for an X Y table I am

converting into

> a CNC router. I plan to use Artsoft mach2 software with Rutex

servo amps to drive the system.

>
> Can anyone give me any more info on the following:
>
> I have a quality 25 mm thick ball nut screw cut to 5 tpi - I have a

choice of rotary

> encoders from 400 to 2000 steps per rev. I intend to drive the

screw

> direct from my DC servo motor shaft.
>
> Not being that familiar with servo systems (the amps haven't

arrived yet !) I am concerned

> that when I turn the ball screw by hand, a mere fraction of a turn

seems to move the ball nut a long way !

> Can a DC servo system with my proposed setup resolve enough

resolution to move the ball a few thou,

> typically for fine, milling depth cuts for finishing etc.
>
> Any info would be most appreciated
>
> Rgds
>
> Dave Fisher
>
>
>
> [Non-text portions of this message have been removed]

Hi Dave,

the simple starting point is that 5 TPI means 0.2" per revolution.
An encoder that output 400 points per revolution would resolve that
to 0.0005"

how fine of a resolution do you want or need ?


Dave