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

On Sun, 2003-06-08 at 20:05, Mariss Freimanis wrote:

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

I posted some links to servo motor datasheets. Some motors have
continuous ratings of 1/3 of their peak torque.

> 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...>
>
>
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--
Kim Lux <lux@...>