Re: Allegro 2961 uptdate

>
> This is obviously a resonance. Are you doing this with the motor

just

> sitting on the bench? You will always get resonance that way.

When the

> motor is connected to a machine, it should do much better, as the

machine

> provides damping. There are viscous dampers used in cases where the
> machine doesn't provide enough damping. It is basically a disc

shaped

> chamber with a free-floating steel or lead "washer" inside, and

filled with

> a thick oil or grease. There are more primitive versions that have

a

> free floating steel plate held loosely between steel plates that are
> attached to the shaft. There is a rubber sheet between the

floating plate

> and the driven plates. The concept is the same. When resonance

ocurrs,

> there is a rapid rotational vibration in the motor shaft, and the
> free floating plate doesn't follow that vibration, just the steady
> rotation of the motor. The friction between the disc and chamber
> or plates dissipates the resonance, preventing it from building to a
> level that could cause steps to be lost.
>
> > I have tried changing some things but no help.
> > Does anybody know any tricks that help with this mid-range
> > instability?
>
> If you are doing this with the motor free, install it in

something. If the

> problem persists, then you can think about dampers. Driving the

leadscrews

> with toothed belts also seems to provide just a little extra

damping.

>
> Jon

You are quite right Jon. They were just sitting on the bench. I
briefly hooked them up to the machine and they seemed to do much
better, though I was not able to get a pulse count. They seemed to
move the machine plenty fast enough. It seems as though some
cushioning would be nice for very slow step rates. Even with belt
drive it shudders from the sudden step. Half step is much smoother.
Lonnie