Re: [CAD_CAM_EDM_DRO] Re: Novice - Stepper Motor questions

In a message dated 22-June-00 14:40:07 Central Daylight Time,
lgpcox@... writes:

<< How could I test a surplus stepper motor for torque ? (oz inch)

When a stepper motor has a rating of NN oz inches, is that holding or
turning torque? (or is holding and turning torque the same on stepper
motors?) >>

Though crude, if done with reasonable workmanship, you can get a very close
approximation with a "pulley-wheel" of exactly 2" (pitch-) diameter, and a
cord fastened to a point on that, at least 1/2-turn around, and hang weights
on the cord. This gives you exactly [that many ounce-]inches of load-torque.
Then, when your motor can no longer "lift" that as you step it, that is a
hair over its torque at that particular stepping-rate (yes, lots of handling!
Might need a wider pulley-wheel and more cord!). "holding torque" is the
amount of torque just-less than that you figure when the weight added
JUST-"breaks" the motor's hold, when DC-energized, no stepping. Simple.
Takes SOME "fussin' with it", if you don't have a precision lab-dynamometer
(which I never saw, myself, even in collige!) This is NOT a dumb question!
Good thinking! Oh, and, no, "holding torque" is NOT the same as "running
torque"; also, the latter varies, depending upon stepping-rate.
Superior-Electric (Warner-Dana) has nice glossy catalogs with nifty
torque/stepping-rate graphs for each make of motor they are trying to sell
you. Those catalogs are usually very, very educational about steppers! Just
try their web-site! Here's a link for you:
<A HREF="http://www.warnernet.com/sem_prod.html">Warner Electric SLO-SYN
Product Overview</A>

Lemme know if you have other "Novice questions"! I can handle those! It
would be the "experienced user questions" that I couldn't handle!

Jan Rowland, Troll