Re: stepper vs. servo

As you said, it's been covered (ad infinitum) before...

So I'll just burrow to the depths of it all, and say:

1)Servos are faster, at the expense of some extra components and
wiring. It used to be a given that they would cost more, but nowadays
step-servos have closed the gap to the point that you are having as
rough go of deciding<G>
1a) Servos require tuning, and they may require additional tuning
over time. Steppers won't.
1b) An inexpensive step-servo MAY not be as accurate as a stepper
system. But it will have more force at higher speeds than a stepper
system.

2)When a stepper fails, it stops. Stall a stepper and it
doesn't "care". Often when a servo fails, it runs at top speed as far
as it can. Until something stops it. Stall a servo, and things burn
up.(hopefully just a fuse.)

3) Servos typically require a larger power supply (more amps) than
steppers(assumes chopper step drives).

4) Servo resolution may be changed by changing encoders. Can't do
that with steppers.

That's really it, IMO.
Ballendo



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "plastiguy" <plastiguy@a...>
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) and each of which fit
> comfortably into my budget and each of which are addressable with

my

> software of choice Mach 2 AND each of which offer the resolution
> (depending on manufacturer) I desire. So, I'm finding it more and
> more difficult to commit one way or the other. Given these

equalities

> for my specific application, I'm beginning to think that in the

end,

> from a performance and features standpoint, there'll be no
> significant difference. Oh sure, I know the stepper-advocates will
> point to the consumable brushes on the servos, and the servo-camp
> counters with...well, something equally relatively minor, but are
> there big glaring pitfalls and upshots for these different means of
> moving junk around that I'm missing? I'm a believer in "You get

what

> you pay for" so I don't want to sacrifice anything important just

to

> save a few bucks and go with steppers, whle I also don't want to
> throw money away by integrating servos when, once the covers are

put

> on the machine, I'll never even detect the difference in having put
> the servos on instead of the steppers.
> Hope I'm missing something so I can GET ON WITH IT!
> Scott