'''Computer numerical control''' ('''CNC''') is a computer "controller" that reads [[G-code]] and M-code commands and drives a [[machine tool]], a powered mechanical device typically used to fabricate components by the selective removal of material. CNC numerically interpolates the points along a cutting tool's toolpath and directs the [[servomechanism]]s that translate the data into movement. The operating parameters of the CNC can be altered via the Master Control Unit (MCU) of the machine.
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==Historical overview==
CNC was preceded by [[numerical control|numerically controlled]] (NC) machines, which were hard-wired and their operating parameters could not be changed. NC was developed in the late 1940s and early 1950s by John T. Parsons in collaboration with the [[MIT]] Servomechanisms Laboratory. The first CNC systems used NC style hardware, and the computer was used for the tool compensation calculations and sometimes for editing.
Punched tape continued to be used as a medium for transferring G-codes into the controller for many decades after 1950, until it was eventually superseded by [[RS232|RS232 cables]], floppy disks, and now is commonly tied directly into [[Computer network|plant networks]]. The files containing the G-codes to be interpreted by the controller are usually saved under the .NC extension. Most shops have their own saving format that matches their [[International Organization for Standardization|ISO]] certification requirements.
The introduction of CNC machines radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action have been dramatically reduced.
With the increased automation of manufacturing processes with CNC machining, considerable improvements in consistency and quality have been achieved with no strain on the operator. CNC automation reduced the frequency of errors and provided CNC operators with time to perform additional tasks. CNC automation also allows for more flexibility in the way parts are held in the manufacturing process and the time required to change the machine to produce different components.
