Re: Servo questions

Jon,

I just checked out the Herbach & Rademan catalog and the Surplus Center
catalog and did not see anything I recognized as a suitable motor to use for
a servo system. Do you know of any listed in their current catalogs that
would work well?

I did just pick up the tape units today that had the motors I was asking
about earlier. I put an VOM on them today and the measure about 6 ohm. Don't
know if they will work for anything, but I got 4 of them for $5.00 each and
figured I could always put them to use in something if they are not suitable
for a servo system.


Tim
[Denver, CO]

> -----Original Message-----
> From: Jon Elson [mailto:jmelson@...]
> Sent: Sunday, June 20, 1999 12:18 AM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: Re: [CAD_CAM_EDM_DRO] Servo questions
>
>
> From: Jon Elson <jmelson@...>
>
>
>
> Dan Falck wrote:
>
> > From: Dan Falck <dfalck@...>
> >
> > In the interest of getting a FAQ started, I thought I might ask a few
> > questions for general reference.
> >
> > This one's for Jon, Matt, or anyone else doing the servo
> retrofits using
> > EMC, Allen Bradley, etc...
> >
> > What size, rating, brand servo motor do you recommend for a
> Bridgeport or
> > mill/drill retrofit?
>
> I have motors rated at 1/8 Hp, 1725 RPM, continuous. That comes to 1.54A
> at 75 V. I run up to about 5 A on these motors during
> acceleration. These
> motors are certainly strong enough, with 2:1 gearing from the motor to a
> .2" lead ballscrew. I hit the wrong button once, and the vise
> moved over and
> broke a 3/8" end mill clean off in the spindle (while it wasn't
> rotating)! It
> didn't cause an axis lag error, overcurrent trip, or anything.
> You can figure
> out what the torque of a 1/8 Hp motor would be at 1725 RPM. My motors
> work out to about 70 oz-in nominal, but I boost it at peak by
> about 3. So,
> that comes out to 210 oz-in. Remember, that is with a 2:1 step-down
> between the motor and leadscrew. So, it would deliver 420 oz-in to the
> screw. I think this would be enough for any Series-I Bridgeport.
>
> > What else should come with or be coupled to the motor? (tach,
> encoder, etc...)
>
> A tach on the motor would save you some trouble. Since I had none of
> that on my motors, I added the tach outboard, using some tiny W. M. Berg
> instrument drive belt. The encoder should be directly on the
> leadscrew, and
> that's how mine is set up. I have a helical-slot compliant
> coupling between
> the screw and the encoder, to protect its' sensitive bearings.
>
> > Where would a person purchase this type of motor? I know they can be had
> > from old tape drives, but one can't always find them laying around.
>
> Herbach & Rademan, in NJ, and Surplus Center in Lincoln, NE, are two real
> good sources for motors. C & H Sales in Pasadena, CA, is also
> good, but they
> know the good servo motors and price accordingly.
>
> Jon
>
>
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