Re: step/dir inputs to servo controllers

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "bull2003winkle"
<bull2003winkle@y...> wrote:

>
> > It appears the Geckodrive is set up to run a servo with stepper

motor

> > inputs. It is not at all clear to me how this differs from step

and

> > direction aside from some simple logic changes.
> >
> > I'd be happy to hear from someone who really understands this.
> >
> > Bob
>
> Bob:
>
> The Gecko G320 and G340 drives are designed to allow a stepper
> controller to run brush DC servomotors. The way it works is to

provide

> PWM directional DC to move the motor and reads a shaft encoder on

the

> motor to know where it is.
>
> The logic to do this is not simple. The drive keeps track of step
> pluse inputs and looks at the motor encoder. It drives the motor at
> such a rate that the pulses from the encoder are equal to the step
> input pulses. It also deals with a number of other problems to keep
> motion stable. It does all the math to adjust for different encoder
> resolutions and the number of step pulse input per turn.
>
> The result is that a stepper controller "thinks" it's driving

steppers

> when the are really DC servomotors.
>
> Hope this helps;
>
> Ken

I am retired and have been slowly improving my home machine shop.
I am thinking I may buy a set of Camtronics equipment (using Gecko
drivers) for CNC but have been unclear as to going for "steppers"
or "servos".

bull2003winkle's information on the way servos are contolled using
Gecko G320 and G340 drives is welcome.

But now may I ask questions for whoever wishes to point me down the
right path. I want to get good finishes and work to .0002 to .0005
in boring small engine cylinders using a lathe.

I have been thinking that servos (with their necessary encoders)
would do the job better because the encoder data could be processed
and produce DRO data. I felt that having the realtime DRO data would
help me in keeping the process of boring under better control by
stoping the machine between passes measuring the cylinder and putting
in new values of Y axis data as necessary. This is sort of manually
controlling a CNC machine to get the most possible out of it in
accuracy.

So here are some questions:

# 1 Is there DRO like information available with steppers as well
as servos?

#2 If so what is the source and how is it displayed if it is
displayed? Is the answer different with different software packages?

#3 Since the DC motors have brushes is their life a lot shorter
than steppers? Also don't the brushes make a lot of electrical
noise that must be suppressed and filtered?

#4 If DC servos are "better" than steppers would it not be even
better to use brushless servos and avoid the sparks of brushed
motors? Does Gecko have a version that drives brushless DC motors?