History of CNC Machines
In the years which followed World War II, the needs of the aerospace industries made demands on the capabilities of machine tools which could not be met by the conventional designs. Using techniques which has advanced rapidly during the war period, machine tool designers and electronics engineers co-operated to build machine tools to produce profiles and shape which is previously could only have been copied from a master template. Templates of this type often are produced by hand methods and are expensive and subjected to inaccuracies which are some times quite unacceptable. Large templates and associated copying methods increase the problems in producing accurate work piece. Today thousands of NC machines are in use. They are used for accurately drilling few holes in a simple pat or for contour milling a complex shape which is practically impossible to machine by conventional methods. Even though the amazingly rapid growth of NC machines did not start until about 1960, the achievement was the result of work done by many people starting in 1947.
1947 was the in which NC was born. It began because of an urgent need John C. Parson’s Corporation, Traverse city, Michigan, a manufacturer of helicopter rotor blades could not make his templates fast enough. So in 1947, he invented a way of coupling computer equipment with jig borer. Mr. Parson used punched cards to operate his digitron system.
1947 was the year of another urgent need. The U.S. air material command realized that parts for its planes and missiles were becoming more complex. Also as the design were constantly being improved, changes in the drawings were frequently made. The servo mechanism laboratory of the Massachusetts Institute of Technology [MIT] was the sub-contractor. In 1951 the MIT took over the complete job and in 1952, the prototype of today NC machine was successfully demonstrated. The term Numerical control was coined at MIT, so by 1953, he potential usefulness of the NC concept had been proven.
In 1955 about seven companies had tape controlled machines exhibited at the machine tool shown. Most of these were different types of several hundred thousands of dollars and some required trained mathematicians and computers to make the tapes for their complex work however the machine tool manufacturers soon realized that NC was an idea which could also be used in many simpler ways.
In 1960 according to the American machinist, there were one hundred NC machines at the machine tool show in Chicago. Most significant was the fact that the large majority of these machines were for relatively simple point to point applications and sales of NC machine increased very rapidly.
During these years, and continuing to-day, the electronic industry was busy and first miniature electronic tubes were developed, then solid state circuitry and then integrated circuits. Thus the reliability of the controls been greatly increased and they have become more compact and less expensive. At the same time intricate control systems are being developed to do jobs and functions which had never been thought possible.
NC Controller Technology
The hardware technology in NC controls has changed dramatically over the years. At least seven generation of controller hardware can be identified as follows.
- Vacuum tubes 
- Electromechanical relays 
- Discrete semiconductors 
- Integrated circuits 
- Direct numerical control 
- Computer numerical control 
- Microprocessors and Microcomputers