What does CNC stand for?

CNC means Computer Numerical Control. This means a computer converts the design produced by Computer Aided Design software (CAD), into numbers.

The numbers can be considered to be the coordinates of a graph and they control the movement of the cutter. In this way the computer controls the cutting and shaping of the material

HOW THE COORDINATES WORK

The way coordinates are used can be seen opposite. The X, Y and Z axis control the movement of the cutter on a 3D CNC machine. This allows materials to be machined in three directions (3D manufacture).
The plastic block shown below has been shaped on a CNC machine. It started as a cube.

The design (produced on CAD, Computer Aided Design software) has been converted into coordinates. The cutter is instructed to go from one coordinate to another. A simple plastic block such as this may have a thousand coordinates.

From:  technologystudent.com