Re: [CAD_CAM_EDM_DRO] servo or stepper size selection

Jan,

I have to disagree with you here, I keep reading on this list how much
cheaper stepper systems are than servo systems, and how much easier they are
to set up, but I don't think that is necessarily true. Sure, if you are
going to go with a full analog system the servo system will be more, but if
you are going to use Gecko's or other step and direction type drives. the
price is about the same.

Drives - the gecko servo and stepper drives are about the same price, maybe
a few dollars difference

Motors - Just one example - Dan Mauch sells a 600 peak oz/in servo motor
with encoder for $159.00, and a 785 oz/in stepper for $170.00. At anything
more than a few hundred rpm's, that servo will have more torque than that
stepper. On ebay or other surplus sources servo motors are usually much less
than steppers

As far as complexity, a step and direction servo system requires about the
same amount of wires to hook the drive to the motor and computer. About the
only thing more complex is using good shielded cable for the encoder wires,
but you should be doing the same thing for the step and direction wires on
both the stepper system and servo system, so it's nothing new.

Performance - I have used both and I would never go back to a stepper
system. No mid band instability or whatever it's called, just very smooth
motion all the way from a standstill to top rpm. No missed steps, and most
important, if the servo amp has not faulted, you can be 100% sure that the
axis is where it is supposed to be. On a stepper system, there is always a
doubt, that the motor has missed steps on that last circular interpolation
that you had the override set too high on.

I keep reading to buy the best you can afford when building your machine,
then in the next sentence, someone will suggest going with steppers instead
of servos. I guess I should be happy, as the $50.00 servo motors on ebay
have less bidders.

What is the opinion of those on the list who have switched from steppers to
servos, as to price and performance comparasion.

Bill

> In a message dated 1/2/2003 1:53:04 PM Central Standard Time,
> mark@... writes:
>
>
> > I have a pc for the job now im
> > looking for best or should i say reasonable way to go, servo or
> > stepper ive been on ebay and looked at many sites for home cnc
>
> Mark: Go with STEPPERS! MUCH simpler, particularly for a "NON-electronic
> person", and less expensive in terms of $-outlay. Gecko Drives might do

if

> you select the correct-size stepper-motors. Lotsa luck!
>
>
> [Non-text portions of this message have been removed]
>