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----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, June 10, 2002 9:44 PM
Subject: Re: [CAD_CAM_EDM_DRO] Pancake servo motors?


> bsptrades wrote:
>
> >
> > Hi all I have been exploring various refits and following along with
> > various threads bu I
> > don't see anyone mention the ironless type pancake motors.
> >
> > For electric controls we have been using the ironless pancake style
> > motors exclusively
> > for years now. These motors such as the Kollmorgen servodisc or
> > Infranor motors would
> > seem also ideal for high performance servo systems on machine tooling.
> >
> > The rotor design provides almost zero cogging , very long brush life
> > in brushed models due to the low inductance, very high acceleration
> > rates and peak torque. It also seems the flat package would just look
> > nice compared to a big long servo motor sticking out in some
> > applications.
> >
> > Does anyone have experience as to why these type motors are not
> > appropriate I really don't see a down side other than the diameter
> > and non NEMA mount which would seem easy enough to get around?
> >
> > Anyhow just a question as there are a lot of experienced folks out
> > here.
>
> Generally, these motors can not provide the torque required to move
> a Bridgeport-size milling machine without a large gear down ratio, which
> defeats the advantages. I get about 18 in-Lb with my somewhat wimpy
> servo setup. That is about 288 in-Oz. Maybe some of the newer motors
> with rare-earth magnets can do this, but the original Kolmorgen and
> Micro-Switch printed motors definitely could not. The high acceleration
> is meaningless when you are moving a 200+ Lb. machine table around.
> These motors, in computer tape drives, can accelerate from zero to
> 3000 RPM in a millisecond or so. But, not when moving a 200 Lb
> table, rather than half a gram of computer tape.
>
> One other thing is that iron-rotor motors can handle peak power sustained
> over several seconds, while printed motors have VERY limited durations
> at peak power.
>
> Jon
>
>
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