I am trying to use a ULN2003 stepper motor controller and I was wondering how to add two more so I could make a small 3d printer.
Find some that are MOSFET based instead, will run much more efficiently. Look at www.pololu.com
Would the motors that can be controlled by a ULN2003 have enough torque for a 3D printer.
Most small 3D printers use bipolar stepper motors with drivers such as the Pololu A4988
There is a simple system for a crude estimate of torque in Stepper Motor Basics