Computer Numerical Control (or CNC) refers to the automation of machine tools, such as lathes, drill presses and screw machines, which are used in the 'machining' process in which such tools cut metal components to desired dimensions. These machine tools are operated by abstractly programmed controls which are encoded on a storage medium, the most commonly used examples in modern CNC production processes being the highly automated CAD (Computer Aided Design) and CAM (Computer Aided Manufacture). Both of these processes play vital roles in CNC turning, CNC milling and CNC machining.
The use of CNC machining, compared to manual machining, allows greatly improved accuracy, productivity, efficiency and safety as (due to reduced human interaction with the machinery) operators are placed at less risk. Also, CNC machines are able to run unmanned for longer periods of time and in the event of a error or problem occurring, the CNC software automatically ceases its operation and pages or calls an off-site supervisor. Also, CNC production allows for greater speed of production as parts that would require multiple steps to manufacture otherwise can be produced quickly by the automated equipment.
Turning is the process when a single point cutting tool is parallel to the material. The material (be it metal, wood, plastic or stone) is then rotated and the cutting tool traverses across 2 axes of motion in order to produce exact depths and diameters. This can be done on the outside of the material or on the inside (in a process known as boring) which can be used to produce tubular components to various required dimensions. This process could be done manually but nowadays it is more common to use a computer controlled and automated lathe which, unlike in the manual process, does not require constant supervision by an operator.
CNC milling involves the use of commands or G-codes programmed into the milling machine with each alphanumeric code having a designated function to be performed by the machine. The mills then drill and turn along axes to cut and shape the material to the dimensions programmed into the machine. CNC milling machines can be controlled using the computer controls or the manual overrides which are located on the front of the machine. Although the program is the preferred means of controlling the process, as the spindle can be programmed to make any required cuts, using the manual overrides allow the operator to speed up and slow down when necessary.