Re: Geckos, Servos, VFD and twitching on Z axis

Your spindle motor drive is an enourmous noise maker. Isolate it with
an RF line noise filter (Corcomp or similar). It will make all your
troubles go away.

Mariss

-- In CAD_CAM_EDM_DRO@yahoogroups.com, "Raymond Heckert" <jnr@a...>
wrote:

> How close to the Z-axis controller to the VFD? Maybe the
> electrical 'noise' is causing problems. Are you using the
> quill as the Z, or are you raising & lowering the table to
> effect a Z-move? Is your ram rigid enough to prevent it's
> movement under power? Does the 'drifting repeat itself
> with any kind of regularity, under load? These are all
> things I'd take into consideration in troubleshooting.
>
> RayHex
>
> ----------
> > From: yethdear0 <da-mack@e...>
> >
> >
> > Hiya,
> >
> > We have an old Hurco knee mill that we have stripped and
> retro-ed
> > with a pc, CNCPro, Geckos and a Baldor VFD for the
> spindle motor. We
> > just got it all up and running but have a problem with
> the Z axis
> > servo or controller. Using a travel indicator on the Z
> axis, the
> > movement is smooth and exact. We have the machine running
> a program
> > that move Z -.100" pauses for 1 second and then moves Z
> +.100" and
> > then runs in a loop. When we turn on the VFD and the
> spindle, the Z
> > axis seems noisy and the travel on the indicator will
> start to
> > drift .001" to .005" each time the program cycles. The
> drift is
> > random, sometimes positive and sometimes negative but
> positive the
> > majority of the time. When we slowed the motion to 1 ipm,
> you can
> > see the motion twitch at random during the movement. This
> only
> > happens when the spindle is running and only the on the Z
> axis. We
> <snip>