The History of CNC Machining

The History of CNC Machining

The concept for modern numerical control (NC)- the forerunner to today’s computerized numerical control (CNC)- was originally conceived c.1947 by John T. Parsons (1913-2007) and Frank L. Stulen (1921-2010) at the Rotary Wing Branch of the Propeller Lab at Wright-Patterson Air Force Base, in Dayton, Ohio as a result of the US Air Force’s (USAF’s) search for a system to design and manufacture more accurate and complex airplane parts (Source: Early on, Parsons and Stulen developed a helicopter-blade template fabrication system using an IBM 602A multiplier to calculate airfoil coordinates and feed data points directly into a Swiss jig-borer, which impressed their USAF research colleagues. Shortly thereafter, Parsons and Stulen developed a unique, computerized, punch-card program to render complex 3-D shapes, leading Parsons to start his own company, Parson Corp., operating out of Traverse City, Michigan.

In 1948, representatives of the US Air Force (USAF) visited the Parsons Corp. headquarters and Parsons was awarded a contract to make new and innovative wing designs for military applications. This, in turn, led to a series of USAF research projects at the Massachusetts Institute of Technology (MIT) Servomechanisms Laboratory, culminating in the construction of the very first numerically-controlled, albeit awkward, machine prototype. To accomplish this, Parsons purchased a Cincinnati DK Series, 28-inch Hydro-tel verticle-spindle contour milling machine consisting of a table and spindle that moved along X, Y and Z-axes. Over the next two years, the Cincinnati was disassembled, significantly modified, retrofitted, and reassembled. As application studies proceeded, the prototype was augmented to produce a motion of the head, table, or cross-slide to within 0.0005″ for each electrical impulse fed by the director. To ensure the prototype was functioning as instructed, a feedback system was added. In response to movement, synchronous motors geared to each motion produced voltage. This voltage was sent back to the detector for comparison to the original command voltage.

By 1953, enough data had been culled to suggest practical, aeronautic applications, and the Cincinnati prototype, which employed a Friden Flexowriter with its 8-column paper tape, tape reader, and vacuum-tube control system, became the de facto prototype for all successive developments. To this day all CNC controlled machines, even the most sophisticated still require three basic systems to operate: a command function system, a drive/motion system, and a feedback system.

Although CNC gained slow acceptance throughout the ’50s, in 1958 MIT Servomechanisms Laboratory developed g-code, which has become the most universally used operating language for CNC devices.

In the early ’60’s the Electronic Industry Alliance (EIA) standardized g-code and computer-aided design (CAD) became a nascent technology providing a firmer technology foundation. As a result, CNC soared and began steadily supplanting older technologies.

By the ’70s, minicomputers such as the DEC PDP-8 and the Data General Nova made CNC machines more powerful and cost-effective. US companies responsible for the CNC revolution, focused on high-end equipment. German and Japanese companies sensing the need, began producing smaller, less expensive CNCs, and since 1979 they have been outselling the United States.

Finally, PCs have now made CNC controls even cheaper, making way for the use CNC-controlled machines for the hobby and general purpose markets. CNC control language now known as LinuxCNC (formerly known as Enhanced Machine Controller, or EMC2) continues to thrive, as are many other CNC technologies.

Adrian Thomas is an experienced interior designer and architect based in the San Francisco Bay Area. To learn more about CNC machining visit,

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