Re: CNC Servo motor gear ratio: overheating. EMC step rate. Tablespeed

Kim,

Servo motors have a maximum continuous torque rating which is between
1/10 and 1/5 of the motor's stall current.

Assuming 1/5, your motor's continuous torque would be 600 / 5 or 120
in-oz.

Current is directly proportional to torque. This current must pass
thru the motor's armature resistance and generates heat. The rated
torque reflects this reality and is the maximum torque that can be
continuously applied without overheating the motor.

At stall the current would be 5 times greater and generate 25 times
more heat than the motor can handle.

Even a 2:1 reduction would cut the torque demand by half and generate
only 1/4 as much motor heat.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> On Sun, 2003-06-08 at 12:52, Jon Elson wrote:
> > Tim Goldstein wrote:
> >
> > Yes your motors will suffer major heating problems set up that
way. If
> >
> > >you want to run at that low an RPM you need to use steppers.
> > >
> > I think not, as his expected load is 2.8% of the peak. These are
very large
> > motors, and he doesn't expect cutting loads, apparently.
> >
> > Jon
>
> I do expect cutting loads. 25 lbs was the empty (ie non cutting)
force
> on the table. We occasionally want to push a 3/4" endmill at 5
ipm.
>
> Could someone please explain to me the difference between the torque
> ratings of servo motors versus stepper motors ?
>
>
> --
> Kim Lux <lux@d...>