Re: [CAD_CAM_EDM_DRO] Re: Servos, Drivers etc. - prices

turbulatordude wrote:

>I have seen some used servos and passed them buy as they were always
>too large, some with one inch shafts...
>
>
>I assumed that since so many of us start out on steppers that servos
>were not only a step up on performance, but a step up in costs.
>
>Has anyone done simple cost comparison between servos and stepers ?
>
>to the motors and drivers cost less, cost more, or about the same as
>steppers ?
>
>I should claify and talk about the larger stepper sizes, say for a
>mill conversion and not a PCB etcher.
>
>

Once you get into the larger sizes, such as NEMA 42 stepper motors, the
servos start to look very attractive. With belt reduction, a servo can
deliver
better performance with a physically much smaller motor. Servos generally
can deliver their rated torque over a very wide speed range, while steppers
lose torque rapidly as the speed increases.

Steppers are resonable at the mini-mill size, but when you get up to
Series-I Bridgeport size, the compromises become substantial. When you
get to Series-II size, they are a mistake. The cost of even surplus
steppers
in the NEMA 42 size is usually high, unless you get lucky. The cost of
servo amps had been high, but Gecko drives and Rutex have brought that
down, for step/dir servos. For true analog servos, Copley Controls is
quite good, although a little higher than the Gecko and Rutex.

Jon