Re: [CAD_CAM_EDM_DRO] access to Ametek motors- suitable for Servo application?

Earl wrote:

>Hi everyone..
>Im in the pre-building my next CNC mahine phase. Iv been useing
>steppers up till now and am wanting to move over into servos.
>
>I have the opretunity to purchase some Ametek DC motors which *look*
>like they would be suitable for CNC aplication. I plan to use Geckos,
>etc.. with about a 36V or thereabouts supply.
>I would be much appreciative if someone could help me out in deciding
>to get some of these motors or not.
>here are some links to some pictures:
>
>motor #1
>http://www.geocities.com/johnperezinc/ametek30v.jpg
>has markings:
>"130687K7
>961510-201 Rev. E
>01A (E56617) 116400-00
>30 VCD Nominal"
>
>motor #2
>http://www.geocities.com/johnperezinc/ametek50v.jpg
>has markings:
>"160590F7
>35-001000-001E
>01A (E56617) 116150-02
>50 VCD Nominal"
>
>Motor #3
>http://www.geocities.com/johnperezinc/ametek72v.jpg
>Claims its a 72VDC motor.
>has markings:
>"260287F7
>01A (E56617) 116449-00
>A35D20067-01
>6989"
>
>All i know is the Nominal Voltage on each and that they do not have
>encoders.. In not even sure if they have access to the shafts on the
>backside for mounting anything to them..
>They are being sold as wind generators and/or battlebot motors.
>
>

Well, this just isn't enough info. Given the RPM at X Volts, that gives you
a lot more to work with. Otherwise, I can't tell anything else about these
motors.

The standard Ametek motor that lots of people use (36 V @ 900 RPM) have
pretty high armature resistance. I'd suspect that any other motor they
make in
the same frame would be wound the same way. it seems that these motors
don't allow a Gecko drive to reach its proper performance in terms of DC
gain. In other words, you can take the shaft of the motor and move it maybe
10 - 15 degrees with VERY little resistance, then the Gecko starts pumping
current through it and it resists the deflection. I haven't gotten any
explanation
from Mariss as to why it behaves like that, it isn't supposed to! My own
servo drives get very stiff, and reach full current with a deflection of
.001"
or so, which is a small fraction of a degree. I am assuming that either
the inductance
or series resistance of these motors prevent the I term of the PID
control loop
from working properly. And, it appears, although I haven't tested it,
that this
may only apply to the Ametek motors. I've had several people report similar
behavior with Ameteks, and no other motors.

>Anyone have any experience with anything like these? Are these
>anything like the "other" Ametek servo motors available around?
>
>

Yes, I think they are the same frame, just with different windings.
They can
change the number of turns/coil and the wire gauge to set the volts/RPM
where the customer needs it.

Jon