How do I wire up this stepper motor? is it even compatible? The reprap stepper motor instructions mention “nema23” as a general type of stepper motor. Not sure if any of the motors covered match this particular model from automation direct: STP-MTR-23055 MOTOR, STEPPER, 166 OZ-IN, NEMA 23, BIPOLAR. Show here:
Prometheus Fusion Perfection 
hint from IRC:
usually the striped white lines are the middle coils
however in our case the colors are red, green, black, white.
here is the spec sheet:
Click to access surestepmotors.pdf
This is helpful too:
http://www.reprap.org/bin/view/Main/Stepper_Motor_Driver_1_2#Output
looks like the mapping is
A = red
B = white
C= green
D = black
The stepper motors that I worked with were basically sold as a kit with a controller. You plug the controller into 120 volt house current. Connect the controller to the motor (one pigtail), program the controller and off you go. The system is one “black box”. The units (controller and motor) are very cheap. All engineering is done.
Francis Zalewski
NEMA 23 is a standard frame size made by lots of different Mfgs.
You can get more torque out of the running motor by using an L/R drive and even more with an L/4R drive. (Assuming your transistors can handle the extra voltage)
What this means for L/R is doubling the power supply voltage and adding a resistor = to the winding resistance in series with the motor. For L/4R you use 4X the winding resistance and 5X the motor voltage.
The Wiki is not bad for the basics.
This pdf is better.
If you have any questions just leave a comment here and I’ll get back to you. Or you have my e-mail. Or leave a comment on my blog.
A constant current drive is best for highest torque at speed. If you want to build one of those I can give you some plans. Let me know.
OK. I see your drive is a chopper drive. Forget L/R. So that is cool. Use the highest voltage your transistor chip is rated for. It looks like 46 V so a 24 V supply is the nearest standard. Although SGS suggest 36V which would be better.
High speed is not so important when extruding/cutting but it does help cut the traverse time.
BTW FORTH software is much better if you are designing your own. Experiments are easy. And I have a neat way of implementing the diagonal line algorithm if that interests you.
BTW a good way to test to see that you are not missing steps is a dial gauge.
Set your set up so that there is a reading on the dial gauge and step away from it at your maximum speed and see if you can come back to the exact same spot on reverse.
If not slow the step speed. Try again. If you still can’t do it, get a higher torque (longer) motor in the same frame size.