Re: mill threading, Acceleration, Axis

Jon,

Thanks for the reply. It sounds quite evolved. I was thinking more of
an empirical method? It that's possible. I will examine the speed
curves again, to see if that can help me.

Alan

Jon Elson wrote:

>
> Alan Marconett KM6VV wrote:
>
> > In a related topic, is there a way to determine the "best" acceleration
> > curve for a stepper motor?
>
> Yes, but it is not easy. You need to get some very tricky numbers
> from the motor manufacturer, such as rotational moment of inertia,
> 'viscous' damping (which isn't really viscous, but comes from eddy
> currents in the stator) and such. You then combine these figures with
> rotational moment of intertia from the rest of the machine, and compute
> where the resonances are, and how strong they are. If they are strong
> enough, you have to stop right there and either make the machine more
> rigid or add a real viscous damper (one of the best is a hollow, fluid-filled
> disc with a free-floating steel disc inside) to damp out those resonances.
> Then, you can compute the required torque to provide the desired
> acceleration, and work from there to find an acceleration that will not
> exceed the motor's available torque at any speed along the acceleration
> ramp. Motor and drive makes have torque vs. speed curves for various
> combinations of motors and drives. They are extremely informative
> and useful.
>
> Jon