Re: Steppers vs Servos

stratton@... wrote:

> From: stratton@...
>
> I have some thoughts and questions regarding the stepper-vs-servo
> debate.
>
> Steppers are often used on small, simple machines since their open
> loop nature permits simpler electronics and controller design. Yet
> there is always the risk of missing steps under high loads, which I
> get the impression leads people to use rather larger motors than would
>
> be needed with closed-loop servos.
>
> Case in point, I recently used a nice CNC'd bridgeport and noted a 19
> lb/in rating on its servos - which works out to only 304 oz/in. I
> don't know how the performance of steppers vs servos compares to their
>
> relative torque ratings, but it seems like people routinely use 470
> oz/in steppers on machines a lot smaller than bridgeports. So I'm
> assuming the closed loop nature of the servo system permits these
> smaller motors.

Note that this is probably the CONTINUOUS rating of the motor, the peak
rating may
be 4 or 5 x greater.

I think the closed-loop stepper mode is in the works.

Jon