Re: [CAD_CAM_EDM_DRO] servo vs stepper

----- Original Message -----
From: "Steve" <robo_man@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, April 03, 2002 3:21 PM
Subject: Re: [CAD_CAM_EDM_DRO] servo vs stepper


> From: "cdoughtynz" <cdoughty@...>
> >
> > Are servo's better then stepper motors? what are the pro's and con's?
>
> Steppers are stronger when they are going slow (strongest when stopped
> and holding), servos are strongest some where close to their top speed.
When

Servos provide virtually constant torque through their speed range.

> you get a stepper close to it's top speed it doesn't take a lot of force
to
> make it loose a few steps, also unless you build a really nice contrler
> there is a solid 200 steps every rotation, where as the servo 'steps'
> smother. When you are trying to move a servo just a little, IE steping
over
> .005, or just want it to hold in place as the other axes moves, it can
push
> and may even juggle that axes back and forth as it tries to put it self
back
> on location.

Servos and especially those with tacho loops can move very smoothly at very
very low speeds and will tend to operate like stepper motors depending on
the resolution.

> If you never plan to move fast, and are building a simple controler,
then
> steppers are better and cost a lot less. If you are going top rate on the
> controler then a servo is the same or a little less then a
stepercontroler.
> For high speed things servos have it over steppers
>
> > Do servo's come as 3 phase?
>
> All the servos I've worked with and seen are single phase dc. With all
> the servos out there I'm sure you could find nearly any thing you can
> imagine though.

Servos come in both dc (brushed) and ac types.


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