Re: [CAD_CAM_EDM_DRO] Re: Gecko and Servos Again !

wanliker@... wrote:

> How about the following:
>
> What size stepper would this be equivalent to?
>
> 2600 RPM GLOBE MOTORS, #537A274. 30.3 VDC permanent magnet reversible motor.
> The motor has ball bearings and has an optical encoder mounted on the rear.
> The no-load speed is 3780 rpm, no-load current is 0.2 amp. With a load of 60
> oz-in, the rpm is 2600 @ 5.6 amps. This is a very powerful cool running
> motor. The encoder employs a Hewlett Packard HEDS 9100 read head with a
> custom encoder disc. The encoder has a two-channel quadrature output with 512
> counts per revolution. The encoder requires 5 VDC at approx. 40 mA for
> operation. The shaft is 1/4" dia. x 7/8" long. The shaft has a flat running
> full length. The motor has four tapped mounting holes on the shaft end of the
> motor face. The holes are tapped for #6X32 tpi screws. The bolt centers are
> 1-1/16" apart. Electrical connections are made via 3/16" quick connect tabs
> connected to the brush bosses. Dimensions: 2-1/8" dia. x 5" long. Stock
> #DCME9950

60 oz-in is not too great. The maximum amps are not given. Presumably,
3780 RPM at 30.3 V gives a Kv of 8 V/KRPM, which is quite low for servo
motion applications. If 5.6 A is the max continuous rating, Kt is about 10.7
oz-in / amp. This could probably run a small machine, or a large one with
very substantial belt reduction, at the cost of lower rapid feed rate. The
above rating 30 V x 5.6 A = 168 W which is .22 HP. I'm using 1/8 Hp
continuous rated motors on my small Bridgeport mill, with 2.5:1 belt reduction,
and 5 TPI ballscrews. They are adequate, but just barely. I get about
3/4 Hp peak from them, and the rating point is 1725 RPM.

The Bridgeport EZ-Trak (and apparently BOSS 7, too) use SEM motors
with a peak rating of 100 V 26 A, or 3.5 Hp!

I would not want to get in the way of one of these on a rapid movement.

Jon