Re: Rutex Z axis problem--more info

> OHHHH! You may be on to something, there! I've been trying to
> figure out what was going on, but a loose encoder coupling could
> provide EXACTLY this kind of error. It would include a backlash-

like

> effect. If you are not "losing steps", ie. a change in absolute
> position, it
> is not a classic encoder problem like a dirty wheel or weak LEDs.

But

> a shaft looseness could do things like this. Do you ever see the

axis

> twitch
> suddenly?

Hi Jon


No twitching

I'm using glass scales for my encoders. when sitting at idle The
axis pulse back and forth a small amount. I suppose this has to do
with the fact I'm using scales as opposed to shaft mount encoders.
If I set the incremental jog to .001" and make a move the axis
moves very smoothly till it gets to the end of the over travel then
it gently pulsates while it's correcting back.

>
> One other problem could be a bad connection between the servo DAC

output

> and the velocity amp input. I have seen this on my system, too.
> Reseating my
> servo cards cures it for a year or so. Especially if the ground

return

> for the
> servo DAC signal was making poor contact, you might see exactly

this

> symptom.

I'll check all my connections

>
> Anyway, there are two possible sources of the trouble. A sick

tachometer

> or tach cable might also be able to do something like this. One

final

> possibility
> is too low gain on the servo loop. Try making very slow moves.

If it

> always
> moves in jumps, it might just be that this axis needs more gain.

This

> could be
> due to high friction or a weak motor.
>
> Jon

It never jumps. It always moves very smoothly.


Thanks
Derek