A simple 3D printer has three axis, X,Y,Z, each controlled by a stepper motor, plus the extruder controlled by an additional stepper motor. Each dimension is made with linear actuators of various designs. Here I made the x axis by using a recycled HP Inkjet printer head assembly, which consists of a motor, cog belt, the cartridge holder, and the metal arm. Unfortunately, the modern motors found in inkjet printers are mostly 2-wire motors (with optical tapes for positioning) instead of the 4 wire steppers needed for 3D printers. Therefore, I had to find a stepper motor with similar size. The one I found in my junk box was probably from an old floppy disk. There are two problems I had to solve with this stepper motor. First, this stepper is a five wire unipolar stepper, which is different from the 4 wire bipolar stepper needed for the 3D printer. However, I was lucky enough that the wiring is accessible on the stepper casing and I simply disconnected the common terminal which makes it a 6 wire stepper. By ignoring the middle two terminals, I effectively converted it to a 4 wire bipolar stepper. Note that the old disk drives probably used high voltages. The resistance is about 160ohm for the wiring so I guess using 12V battery is ok and that's what I used.
The other problem was that the stepper had no cog wheel on it, so I had to find one from the HP printer that fits exactly and I was lucky in finding one. See the following video to get an idea how it works.