Re: [CAD_CAM_EDM_DRO] stepper vs. servo

plastiguy wrote:

>Group -
>I'm going to go ahead and open up this can of worms (though I'm
>certain it's been done many times before my time in this forum). The
>age old question has popped up again. For a 4x8 CNC router with
>pretty standard mechanics I can effectively use either steppers or
>servos, each of which I can readily find within the torque range I
>need (400 to 600 in-oz, about 200 watts max), and each of which I can
>use with my driver of choice (Gecko G320)
>

Given the Gecko 320 as the driver for the servos, I think there are a
couple of significant advantages over steppers. First, the servos are
usually capable of a greater speed range, while steppers rapidly lose
torque at higher speeds. With servos, you rarely have to worry about
resonance issues. You don't say whether you will use belts, rack and pinion
or leadscrews to drive this machine, but the servo will likely provide
smoother motion, and be less perturbed by some backlash in the mechanics.
Steppers can go wild when rack and pinion drive is used, and rattle the
gears
something awful. Finally, if you lose a step with a stepper drive, you
won't know it until you measure the finished part. With the gecko 320,
it won't allow small errors to build up, and will fault if the drive binds
up or crashes. This can be sensed by the computer and cause it to stop
all axes.

Jon