Re: [CAD_CAM_EDM_DRO] Re: stepper vs servo

info.host@... wrote:

> > Or, on the otherhand, don't overload the stepper and it will be just
> > as reliable and accurate.
> >
> > Mariss
>
> When you see kits for upgrading Sherlines and the likes to CNC are the
> motors (100 - 150oz/in) given as per their peak torque or their constant
> torque? How much constant torque would it take to run a normal sized knee
> mill like a Bridgeport series 1?

Steppers do not have peak torque. because steppers need to waste
power just to hold position, they normally run at the continuous rating
point, and can't be 'boosted' to a higher current for a moment.

Servos DON'T use much power just sitting, and therefore can be safely
booted to higher current for a moment.

But, steppers do have 'holding torque' and 'running torque'. The holding
torque
may be as much as twice the running torque, even at fairly low speed.

I'm using 1/8 HP (continuous) servo motors on my Bridgeport Series 1,
with 2.5:1 belt reduction ratio, and 5 TPI ballscrews. I calculate about
1000 Lbs linear force on the table with this setup.

That motor works out to about 4.4 in/Lb continuous, and 15 in/Lb peak.

Jon