Early Numerically Controlled (NC) machines were servomotor controlled tools that were able to machine precise shapes by following sets of instructions fed into them on magnetic or paper tape or punch cards. These instructions took the form of a series of points through which the controls would move, with the result that geometric forms could be machined far more precisely than if the machines were operated by hand.At first the geometric calculations to generate the points required to generate different shapes had to be worked out by hand by hand, which was a time-consuming process. This was a time-consuming and sometimes imprecise process, but in the mid 1950s computer subroutines were developed to carry out these calculations, and the era of computer numerical control (CNC) had arrived. Computer generation of NC input media was so much quicker and more efficient than manual production that in 1956 the US Air Force accepted Douglas T. Ross to formulate a general programming language for numerical machine control that was based on points and lines. This language was developed into the Automatically Programmed Tools (APT) programming language, which was used to program CNC machines until the 1970s.In 1957 MIT researchers led a team aimed at developing a fully computerized numerical control system using the new APT programming language. By 1959 their work had resulted in the first product ever produced using computer-aided design and manufacturing – an aluminium ashtray.
As computers became smaller and cheaper over the course of the 1960s, it became cost-effective to replace the dedicated servo systems controlling CNC machines with minicomputers.The development of microprocessors in the 1970s led to the widespread adoption of microprocessor control in CNC machines, and today almost all CNC machines are microprocessor-controlled. To some extent USB drives, floppy disks and local area networks have replaced punch tapes in modern CNC systems, however punch tapes are still widely used.
Modern precision engineering has found roles far more diverse than the spindle and cutting tool processes in which it has its roots, and today CNC can be used for any process suitable for machine tool motion platforms.CNC-controlled lasing, welding, flame cutting, bending, gluing, sewing, routing and sawing processes, amongst others are commonplace.