Stepper Motor for High Torque Application

[centralhelp]

We have a small stepper motor that is rated for ~84 in-oz and a load for it to drive, however slowly, of somewhere less than ~10 ft-lbs (~2000 in-oz). Splicing in a gearbox with a better than 1:25 ratio seems to be the best option, but the first one we tried (at 1:48) just couldn't handle the torque. I've hunted down a couple gearheads on the net that claim better than 1:50, but I know sufficiently little about stepper motors to know if we're going about this the right way. I need a cost effective solution to driving the 10ft-lb load repeatedly from a dead stop and we'd like to keep the control interface we have with the small stepper. Any help is appreciated. Thanks.

 

[itsmoked]

The big problem with steppers is that they aren't linear. They provide little spurts of torque. So if they can't get the load to actually get moving during the quick spurt they just kind of flail. Is there any chance you can use a servo motor instead or do you need the stepwise nature?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[sreid]

A gerbox seem correct to me. I think that CGI could supply a gearbox that would mate directly to your stepper motor and handle the torque you require.

http://www.cgimotion.com/

 

[sreid]

Another choice might be a Harmonic Drive gearhead.

http://www.harmonicdrive.net/

 

[MikeHalloran]

Stepping motors should be thought of as rotary impact hammers. Even the tiniest one can beat the crap out of a gearbox, especially a good gearbox, especially when everything is nice and rigid.

I've had good results with timing belt drives and steppers, mostly in 1/5" pitch. I don't care for the really tiny pitches.

Depending on your geometry, you may be able to get 25:1 in one pass with timing belts. One trick; you don't need a full complement of teeth on the big 'sprocket'. Two or three isolated teeth sticking out of a 'minor diameter' drum will work just fine.




Mike Halloran
Pembroke Pines, FL, USA