how to build...continue

Parts Hunting For Part 1 of the How-To, we'll go over all the major components of the project and get started with the controller. The major components of the DIY CNC machine:

• Stepper motors
• drive positioning screw
• 3 Axis stepper motor controller
• Linear slides

The most important component to determine the construction of your milling machine is the motor. Motors can be purchased from surplus houses, but the cheapest place to get them is from old dot matrix printers. Apple Imagewriters are one of our favorite sources. They contain multiple stepper motors, and the primary is pretty beefy. As a bonus, just about every dot matrix printer has a hardened steel rod that can be useful for our nefarious goals.

A stepper motor is an odd beast. Most motors spin when power is applied, stepper motors contain multiple coils. If the coils are energized in the proper order, the motor will rotate a small amount (a step). We'll take full advantage of the nature of stepper motors with this project. To simplify your life later on, you'll want to find stepper motors with more than four wires. Four wire motors are usually Bipolar motors. They produce more torque, but end up complicating the control circuit. The preferred type of motor for the frugal hobbiest is Unipolar. These usually have five or six wires, and they're pretty easy to work with.

Most stepper motors are labeled. The major points of interest include the voltage, resistance and the number of degrees per step.  Knowing the number of degrees per step is vital for configuring the software to properly control the machine later on. For a three axis machine, at the very least you'll want the X and Y axis to both have identical motors. It's not the end of the world if they don't match, but it's more of a pain later on.