Re: Video of my resonance

--- In CAD_CAM_EDM_DRO@yahoogroups.com, John Dammeyer <johnd@...> wrote:

>
> I turned up the volume really high and played the video again. Then I
> looked at your list of parameters. Is it possible that a

combination of two

> things are really happening here? The sound is much like the beat

frequency

> of a twin engine aircraft where the props aren't perfectly synchronized.
> But you state that the motors are slaved.
>
> So here's an idea. What is happening is that at the speed of interest,
> you're at some natural resonance of the entire system even though

you are

> micro stepping. Although the motors are slaved, and each steps N
> micro-steps, they may not be physically slaved where the rotors are in
> exactly the same position. So one motor is at .5 of a full step

while the

> other motor is at 0.75 of a full step. Now if each moves 10 micro-steps
> then each motor will still be .25 of a full step apart but just at a
> different rotor position.
>
> Add that the two racks may not be aligned absolutely perfectly and the
> loading on the motors as they move through there micro-steps will change
> hence the beat frequency as they turn. At higher speeds, the resonance
> situation doesn't exist or if it does it's at a much higher

frequency and

> the two don't happen long enough for it to be noticed.
>
> Just an idea...
>
>
> John Dammeyer
>

I am inclined to agree. the noise sounds more like a freight train
than cogging of a spur gear. I had thought the spur gear at 1" DP
would be tight and cog under normal movement ( 1.5" is preferred for
smoothness.)

If you have a 1.5" gear, try that to get things smoother, at the cost
of less resolution.

As for the out of sync, that would be simple to handle.

I think you could just power off everything (lock the table to keep it
in posistion.

Loosen the motor pulleys so the motors can move easily.

Then tighten the pulleys again.

That should have the motors cog into a natural posistion.

If the tightening of the pulley moves something, then it may go out of
sync.

I could be wrong, so comments are welcomed.

Dave