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Torque Ratings for Stepper Motors

ac4200

Plastic
Joined
Dec 9, 2019
Hello all,
I am building some robotic/automation projects. I know general torque guidlines, but I have maybe a little bit of a more practical question. Question: what are some general guidelines for using steppers in terms of their capabilities. Particulary say for example I use a nema 8: geared correctly can a mechanism linked to it be moved by hand? If I shoved a linkage would it "slip?" What size stepper to create a robotic hand that can lift up a 10lb weight?

Are their some kind of general guidelines for this kind of stuff?
thanks!
 
You can certainly back drive a stepper motor and make it slip. You would need to provide more information regarding your load scenario including:

- the gearing of your particular setup as well as the
- geometry of your hand linkage and load location relative to hand linkages
- speed at which you actuate the linkage
- specific motor you are using

Some benefits of steppers:
Good torque at low speeds (check the torque curves)
Cheap
Easy to drive (step/direction inputs)

Some drawbacks of steppers:
Slippage risk at higher speeds/microstepping - need a healthy safety factor to prevent slippage (again consult the specific motor torque curve)
Low top speed
Large size when compared to DC brushed and brushless motors
Needs encoder for closed loop operation


Some good reading:

Anaheim Automation | Selecting a Stepper Motor System

Anaheim Automation | Step, Stepper, Stepping Motor Basics
 
I deployed a Sanyo Denki stepper system that employed encoder feedback and it was the closest thing to true non-slip servo control we have achieved with stepper system . . . at present, we only use steppers where feedback devices will not survive and accuracy is not critical. We predominantly use brushless servos and AC Induction motors for all of our motion applications.

SANMOTION Model No.PB | SANMOTION | Product Site | SANYO DENKI
 








 
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