Re: CNC Lathe question/ Linear encoders/backlash

--- In CAD_CAM_EDM_DRO@y..., Doug Fortune <pentam@h...> wrote:

> vrsculptor@h... wrote:
> >

<snip>

> There ya go, clear as mud.
>
> Doug Fortune
> http://www.cncKITS.com

Doug,
Thanks a lot.... that actualy makes a lot of sense. I think a ball
screw on the back of the lathe / servo / gecko would be the way to
go.

I've had a conceptual concern about long linear encoders, servos and
backlash for a while. Servos while idling continually do a pretty
quick +/- 1 count dance to keep track of where they are. With a high
count encoder mounted on a lead screw this dance doesn't amount to
much. On my mill 1/4,000 of a revolution. If you used a linear
encoder and there was any backlash at all the motor might be turning
quite a few degrees to move the table an encoder count. This would be
like a jack hammer on what ever is causing the backlash and I could
imagine the whole setup exploding. Any thoughts on this?

I understand that the new generation gecko's do a very slow dance to
minimize this problem.

Roger