Re: [CAD_CAM_EDM_DRO] Re: mill threading, Acceleration, Axis

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