Newbie Build - Ebay Stepper Motor Question

Hello everyone!

I am a complete newbie as far as most electronics go and have limited experience with Arduino but I cant help but want to build a 3D printer and/or a CNC machine. I've been tinkering with my Arduino and some DC motors and recently was able to purchase 2 used printers and a used scanner to harvest the stepper motors out of them. The question I have is does anyone have any experience with these stepper motors?

Stepper-Motor 28BYJ-48

Just wondering if they are quailty or just junk and not suitable for a stable build. Also when scavenging parts, does it matter if they are 4 wire vs 5 wire steppers as long as I can control them with a driver? I mean I understand the differences as far as unipolar, bipolar, etc... but is one more precise than the other?

Also, can I reuse the rods from these machines in the new build?

Thanks!
Tim

5 wire steppers are unipolar only, and hence incompatible with normal RepRap electronics; this type also doesn't have enough torque. 4, 6 or 8 wire steppers are all suitable.

You need some fairly specific motors for a printer. They run $10 to $20 brand new for ones that work with the controllers we normally use. Matching a "free motor" up to a $30 controller does not save you anything.

What you *must* know:

1) The mounting face size (say NEMA-17) there are about a dozen common alternatives
2) The torque output. We use fairly high torque motors
3) The body length (not critical for all locations, but very critical for some)
4) The shaft diameter (many variations ...)
5) The current rating for the windings (enormous variation here)
6) The winding type (4 wire bipolar is the target)
7) The number of steps per revolution (200 is normal)
8) Number of shafts - we use single shaft motors.

That's not to say you *can't* get a printer going from scrap motors, been there done that on other stuff. The issue is that the firmware / cpu / drivers / toolchain / mechanicals tie you into a pretty specific set of parts. The standard "stuff" is so cheap that going off list can get crazy fast.