Re: Pancake servo motors?

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:

>
> 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

Hi jon,
Power is not the problem with disc motors if you have the amplifier
behind it. In the controls application we use these for simulating
control forces at the cockpit control so I'm used to high foot-
pounds not oz. We need the smooth control since these run in a
velocity-force loop meaning the motor is at stall all the time except
dynamic response releases. Have a look at the kollmorgen servo dics
specs these days. A u16 runs continous at 400 oz-in with a 5000+ peak.

I was curious since these are so smooth, I can get a stack of
U12m4's fairly cheap. They are only 280 watt continuous around 118oz-
in with a 1300 oz-in peak. But they are small only 5.5 in dia. 2.5
thick. I thought these would power a router table quite well. They
will do 6000+ rpm max 4000 easy.

You guys are right in the assumption that the application is a waste
of the motors best qualities for heavy machines. The practical
acceleration of a 400 Lb. table is low compared to motor response.

Thanks for the replys it's always fun hashing ideas around.

Brian S Punkar
BSP


http://kmtg.kollmorgen.com/products/product_literature/product_brochur
e/pdfs/KOL1037.pdf