October 2007 Edition
CONTROLLING INTEREST
An Industry Giant Leaves a Lasting Legacy
The intellectual father of NC and CNC has died. While controversy surrounds his involvement with the development of numerical and computer machining, his pioneering ideas can't be denied.
John Parsons died on April 18. He was 93. Why does this matter? It's because Parsons was the father of numerical control.
While we mourn Parsons' death, he leaves the legacy of Numerical Control and Computer Numerical Control.
Numerical Control technology – NC – is the direct descendent of the world's first NC machine tool demonstrated by the Servo Mechanisms Laboratory at the Massachusetts Institute of Technology in Boston in September 1952.
Computer Numerical Control – CNC – like NC, is the separation of programming from operations. The program contains geometry data in numeric form for numerically-directed interpolation of a cutting tool in the work envelope of a machine.
In the early '50s, while professors at MIT were developing numerical control, General Electric was working on a process known as Record/Playback. The GE engineers fitted position transducers on the lead screws of a manual lathe. The transducers returned feedback pulses to a recording device as the machinist made the first part. The recording was played back to power actuators that drove the lead screws for the machine to produce more parts.
The U.S. Air Force, sponsor of the GE effort, declined the use of Record/Playback for two reasons:
First, the machinist was the "programmer" in this method. The Air Force wanted to remove the machinist from the machining process, believing that human-free by-the-numbers machining was a more reliable way to make parts to rigid specifications.
Second, the nature of U.S. aircraft design emphasized avionics, which required a rigid – but light – airframe for the added weight of the electronic devices. The machining required for this production required by-the-numbers machining to cut contours that were impossible by manual means. The U.S. Air Force used its deep pockets to get its way, and in fact, to finance the development of computer-based workpiece programming, Computer-Aided Manufacturing – CAM – as well.
Today, numerical control is still very much the way it was envisioned by the Air Force more than half a century ago, with the significant exception that the role of the operator is generally acknowledged as essential for CNC success. So John Parsons' legacy lives on.
Norman Bleier manages Siemens machine tool applications engineering in support of U.S. OEMs. His special interest is technology on the shop floor.
Who was the real inventor of NC?
In 1948, John Parsons, president of Parsons Works, Traverse City, MI, and an accomplished machinist, initiated a project with the U.S. Air Force to develop a by-the-numbers machining concept. His project was usurped by the Massachusetts Institute of Technology and redefined as 3-axis contouring motion control with a straight-line interpolation function.
The struggle between Parsons and MIT for control of the project reverberates in the CNC industry even today.
The machining industry myth that surrounds Parsons paints him as an uneducated shop floor guy who invented NC. In truth, Parsons was a member of the entrepreneurial class.
He had IBM equipment, engineers, and machine operators in his employ who experimented with by-the-numbers position control. Even with these resources, he consulted MIT for its knowledge of servo drive systems.
In the end, MIT defined, invented, named, characterized, and disseminated NC technology with the support of the Air Force. With Air Force backing, MIT became known as the organization responsible for the NC and CNC revolution.
Parsons aged and nearly blind, at IMTS in 1998, still presented the profile of a decent man who was involved with cold war politics and hardball academics. He deserves our respect for realizing, in a general way, that by-the-numbers could be combined with digital technology and applied to the cutting tool process of stock removal.
His title as Father of NC is deserved. His elevation as an icon of the supposed Second Industrial Revolution is aimed as a blow to the MIT professors for what many consider their usurpation of his project.
The historical record is clear; Parsons did not invent NC as we know it today. That distinction goes to Jay W. Forrester, William M. Pease, James O. McDonough, and Alfred K. Susskind of MIT as shown in U.S. Patent No. 3,069,608, filed August 14, 1952, "Numerical Control Servo System."
On May 5, 1952, Parsons filed the patent claim "Motor Controlled Apparatus for Positioning Machine Tool" for a mechanical device that received numerical information from punched cards and that cut on one axis at a time.
This device, for which he received Patent No. 2,821,187 in 1958, never became a commercial product. It played no role in the development of numerical control technology. Historians of technology have speculated that the machining industry would have been better served with Parson's simpler by-the-numbers concept. Now, the issue is mute.
What do you think?
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www.ModernApplicationsNews.com or e-mail the editor at
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