[Kegonsa]

I am looking for help on stepper motors. I looked through the sticky pages and was surprised that I didnt find anything on it. I am looking for a page that can help me understand more about a stepper motor and how to best select them for a project.

General information I am looking for:
Speed vs Torque
Is more torque always better?
Gearing the stepper and effects that it has- I understand less speed more torque but when do you want to do this
Better understanding on inductance and how it effects the motor

From what I have read if you have a nema 23 and 34 with the same oz rating and inductance then they should perform the same, only difference is the motor size. Is this correct?

Thanks for the help and I will appreciate any good reading that better explains this for a newbie.

[dmalicky]

Some great links:
**http://www.geckodrive.com/gecko/imag...cs%20Guide.pdf
http://www.cnczone.com/forums/faq_cn...rs_servos.html
Stepper Motors

More torque is only better if it's needed. Else it's extra $, weight, or amps. Most guides recommend a 30%-40% torque margin (extra), to not lose steps. The torque a machine needs depends on the gearing/leadscrew, accelerated mass, the acceleration, friction, and cutting forces. Max acceleration is often limited by machine rigidity. Reading what works for other machines and cutting duty is also important.

For a rack-pinion driven axis, gear reduction puts the stepper in a stronger part of its torque curve for typical cutting, and gives more resolution (steps/inch).

For the same holding torque and inductance, a NEMA 23 is likely to have a higher max rpm, faster acceleration (less inertia), and weaker cogging than a NEMA 34. The 34 is likely to run cooler (more surface area) and be heavier. They'll also resonant differently.

[Christian Knüll]

Hi,

the main problem when choosing a stepper is always the question how much torque will I need? For a DIY design this is usually hard to calculate in advance as well as hard to measure. Having too less torque is one of the most annoying things that could happen - so the usual approach is to have a look on similar machines and select something that is known to be oversized.

Smaller steppers are usually faster - but if you don't want to risk to buy twice you better select a stronger one. To achieve higher speeds there are other options: get a stepper drive with higher voltage or a screw with larger pitch.