Computer numerical control (CNC) is the automation of machine tools by means of computers executing pre-programmed sequences of machine control commands. This is in contrast to machines that are manually controlled by hand wheels or levers, or mechanically automated by cams alone.
In modern CNC systems, the design of a mechanical part and its manufacturing program is highly automated. The part's mechanical dimensions are defined using computer-aided design (CAD) software, and then translated into manufacturing directives by computer-aided manufacturing (CAM) software. The resulting directives are transformed (by "post processor" software) into the specific commands necessary for a particular machine to produce the component, and then are loaded into the CNC machine.
Since any particular component might require the use of a number of different tools – drills, saws, etc. – modern machines often combine multiple tools into a single "cell". In other installations, a number of different machines are used with an external controller and human or robotic operators that move the component from machine to machine. In either case, the series of steps needed to produce any part is highly automated and produces a part that closely matches the original CAD.
Examples of cnc machine:
CNC Milling Machine: Translate programs consisting of specific numbers and letters to move the spindle (or workpiece) to various locations and depths. Many use G-codes Functions include: face milling, shoulder milling, tapping, drilling and some even offer turning. Today, CNC mills can have 3 to 6 axes. Most CNC Mills require placing your workpiece on or in them and must be at least as big as your workpiece, but new 3 axis machines are being produced that you can put on your workpiece, and can be much smaller.
CNC Lathe Machine:
Cut workpieces while they are rotated. Make fast, precision cuts, generally using indexable tools and drills. Effective for complicated programs designed to make parts that would be infeasible to make on manual lathes. Similar control specifications to CNC mills and can often read G-code. Generally have two axes (X and Z), but newer models have more axes, allowing for more advanced jobs to be machined.