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