Re: What makes a motor a servo?

>
> a DC motor may have a noticable cog, this is where you can feel the
> steps as you spin the motor. I have a treadmill motor that is a
> really hard cog that needs some force to spin it. Bad.
>

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Pete Brown \(YahooGroups\)"
> <YahooLists@i...> wrote:
> > >>One of the differences between DC servos and DC motors is the
> number of
> >
> > brushes.<<
> >
> >
> >
> > Exactly what makes a motor a servo vs. just a DC motor with an
> encoder on
> > it? I'm curious as I was trying to figure this out last night, but
> couldn't.
> >
> >
> >
> > Pete
> >
>
> I'm very interested in this thread as well.
>
> From what I have been told, there is not difference, but, BUT (big
> but goes here)
>
> a DC motor may have a noticable cog, this is where you can feel the
> steps as you spin the motor. I have a treadmill motor that is a
> really hard cog that needs some force to spin it. Bad.
>
> Many DC motors are rated for high speed, often 5,000 RPM or more

> as a desirable motor will have a speed less than 1,000.
>
> The difference is that you need add gear/belt reducers to get the
> speed up. Servos are best when run at 80% of nameplate. (not
> exactly shure why, espically if you use a 1hp motor in a 1/8 hp
> aspplication)
>
> Servo's with brushes have the brushes in 180.00 degree alignment.
>
> DC motors that are designed for a specific purpose may have the
> brushes aligned at an angle that favors speed or torque for running
> the motor in one direction only and running in the reverse direction
> lacks speed, or power or some such.
>
> Not all motors have ball bearings, but ball/roller bearings are

> desired for CNC work as the reversing is extreemly hard on sleeve
> bearings.
>
> I don't think this is a complete list, but a few pointers that

> have made and I keep in mind.
>
> Dave