Re: stepper vs. servo

Huh?!?!?

Steppers do NOT have brushes. Period.

And step-servos are a faith-based system as well--up to the 128 count
error allowed. More importantly, if one axis hits a tough spot, the
other axes keep on going, changing the geometry of the part being
cut. This can happen continuously--within the 128 counts--during the
toolpath. Only a "REAL"(means non-step-servo, since WHERE the loop is
closed does not matter to the definition of servo, but DOES matter to
the performance) servo can continuously make adjustments to ALL axes
as the following error of any one is increased...

Most important steppers are NOT "what you use when you can't use
servos, for whatever reason, such as cost, size, know how, etc."
There are many cases where steppers are MORE suitable than servos due
to their STRENGTHS... (That's like saying a pickup is what you use
when you can't use a car. They are made for different things, and
each has its place.)

Choose step-servos if you wish. But don't make others feel that
they're somehow "less" if they use steppers. I find the "know-how"
portion of your statement offensive. There are a lot of folks who use
servos because they lack the know-how to properly use steppers..

Ballendo

In CCED, John Johnson <johnatl@m...> wrote:

>Steppers are an open-loop system. Faith based, if you will. In
>nearly all systems, the computer tells the stepper to move, and
>assumes that it has. Servos, being closed-loop, will go where
>they're told, or let you know about it.

>I would go for the servos. Steppers are what you use when you can't
>use servos, for whatever reason, such as cost, size, know how, etc.
>
> Regards,
> JJ
>
>p.s.. Steppers have brushes too. I have machines running 5 to 7 days
>a week, from 1 to 3 shifts, and (servo) motor life is measured in
>years.