Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo

Roy J. Tellason wrote:

>On Tuesday 10 February 2004 06:01 pm, ballendo wrote:
>
>
>
>>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...
>>
>>
>
>Non-step servo? I thought that servos and steppers were two different things.
>Although in going through my box of what I'd thought were stepper motors I
>did find some with attached encoders... What would you call these?
>
>

Many people use Gecko 320/340 drives and Rutex drives which take step and
directions signals from a computer and drive a servo motor from those
commands. When Ballendo writes "non-step servo" he is referring to servo
systems which do not use step/direction signals. The most well-known would
be the old-style analog velocity servo, where the CNC control sends a
voltage
from -10 V to +10 V to the servo amp, which produces a motor velocity
proportional to the command voltage. Zero volts means hold still.

Stepper motors with encoders can be used in many ways. Some of which
may be servo-like, and others may not be at all. For instance, in some
cases
the stepper motor can be turned off to allow an operator to move something
manually, with the encoder keeping track of position. In other cases the
encoder may be to detect stalls and loss of steps, but still not for closing
a positioning loop.

Jon