Re: [CAD_CAM_EDM_DRO] Is a reduction drive necessary for servo motors?

Bob McKnight wrote:

>Peter
>
>It looks like you would have to know the number of steps
>per revolution of both the stepper and the Servo. I am
>not sure how the servos are rated , but the steppers are
>usually rated in degrees per step or steps per revolution.
>I have been led to believe that steppers tend offer a smaller
>incremental movement than Servos
>
>

Servo MOTORS, themselves, have NO steps. They can move in
infinitesimal units. The encoder sets the resolution of the positions
the motor can be commanded to index to. So, if you have a high
resolution encoder, you get high positioning resolution. I have
1000 cycle/rev encoders on my machine, and counting all transitions
gives 4000 counts/rev, so this would be 20 times the resolution of
a standard stepper in full step mode. This is not like microstepping,
where stepper motor steps are broken into smaller units, but there's
no guarantee the motor can move to those smaller increments.
The encoder reads actual position to its resolution +/- some small
error, and the servo drive will attempt to drive the motor to the
commanded position.

Jon