CADCAM Teacher

What is CNC ?

Posted On Mar 04, 2018

CNC stands for Computerized Numerical Control. A CNC machine uses a stream of digital information (code) from a computer to automatically execute a series of machining operations that CNC machines offer to increase productivity and flexibility. CNC technology was developed in the United States in the 1950's for the United States Air Force by metalworking machine tool builders. It was a major advance in the ability of machines to reproduce complex part machining steps more accurately without human intervention or variability.

A CNC machine uses mathematics and coordinate systems to process information of what to move, to where, and how fast. Most CNC machines are able to move in three controlled directions at once. These directions are called axes. The axes are given simple names such as X, Y and Z (based on the Cartesian Coordinate System).

A CNC machine must be able to communicate with itself and the machinist to operate. A computer numeric control unit sends position commands to motors. The motors must talk back to the control that, indeed, they have acted correctly to move the machine a given distance. The ability of CNC machines to move in three (or more) directions at once allows them to create almost any desired pattern or shape. All of this processing happens very fast.

No human can control the movements of a machine as precisely as a CNC. These machines work with very small units of measure. A CNC is able to drill a hole at one end of the worktable, move to the far corner and return to make the same hole again with only a few ten-thousandths of an inch error. The accuracy of a CNC can be explained this way: take a hair off your head and slice it the long way six times. The sliver you have left is about the margin of error with the machine.