[imagineer]

Uni-polar or Bi-polar?
I’m in the beginning stages of building a small, cheap “rough draft” version of a CNC mill, for the purpose of learning, developing and proving out the control software and electronics before I scale up and build a larger, usable machine.

I will be using BobCad 18 to develop the G-Code and Mach 1 (or 2) for the controller software (thanks very much to patmul & pminmo for their very helpful information). For simplicity, it is my intention to use the same type of stepper motors for both the “rough draft” and the future machine.

My question is, should I look to use Uni-polar or Bi-polar motors (or does it matter)? Is there preferred type among CNC builders? Does one type offer more advantages regarding half stepping?

My collection of small steppers (scavenged from old printers and copiers) seems to be all Bi-polar motors, but the only larger projects I’ve done with steppers, involved using Uni-polar motors and homemade drivers (with onboard oscillators)

I expect to build my own 3 axis driver board for the rough draft version (something like this (http://pminmo.com/3axis/3axis.htm) and will most likely purchase drivers for the larger machine.

Thanks in advance,
Mike

[Mariss Freimanis]

Step motors are just step motors; it's step motor drives that are unipolar or bipolar.

Unipolar drives can only work with 6-wire or 8-wire motors. Bipolar drives work with those as well as 4-wire motors.

A half-step drive is really a 2-microstep drive. It makes no difference to microstepping if the drive is unipolar or bipolar.

Mariss