MMS Looks Back: 1950s - NC? What’s NC?

Modern Machine Shop published just hints of numerical control (NC) prior to the July 1956 issue.

For example, the May 1955 issue contains a two-page article titled “Tape-Controlled Boring,” which appears to be the first time the magazine published an article about automated machining as an alternative to manual machining. The brief article presents an application of the “punched-tape principle” of automatic machine operation, describing “a standard four-spindle Ex-Cell-O precision boring machine modified with built-in electronic controls and circuitry and a tape ‘reader’ housed in a specially built control cabinet.” One indication that the potential impact of this type of technology perhaps was not appreciated or apparent at that early time was that this article was not promoted on the May cover as other articles were.

That article was followed by another in August 1955 about a similar technology titled “Tape Automated Machining.” The article describes Giddings and Lewis’ “Numericord” technology, which would use punched magnetic tape to automatically drive machine movements. This story provides more detail about the concept, describing how the system would use a device called a “director” to convert paper to magnetic tape that would be read by the machine control. Still, NC is not mentioned in the article.

The July 1956 issue seems to contain the first specific mention of NC in a feature article (although the words “numerical control” are used only in a photo caption, not in the body of the article). As shown above, this article was cited on the cover that month, however, it was simply referred to as “Machine Control.”

The article is titled “Automatically Controlling Machine Operations,” and its subhead sums up the promise of this new technology.

“A control tape produced on a planning desk in one city could be duplicated by telephone anywhere in the world, placed in a machine control unit, and production of the part immediately started.”

The automated machine control technology explained in the article was developed by Electronic Control Systems, a subsidiary of General Dynamics Corp., and dubbed “Digimatic.” Background information to create the article seems to be based on a public demonstration of its “push-button factory control system” capabilities. Although it would seem this technology would be aimed at large operations, the article explains that the system also would be appropriate for small- and medium-size shops looking to implement automatic machining. The idea was that Digimatic capability could be added initially to only one machine to enable shops to “approach automation cautiously and well within the limitations of their budget,” as the article explains.

There were two primary elements to the Digimatic. First, a “planning desk” with decimal computer and tape recorder was used to create the magnetic tape that was read by a control unit attached to a modified milling machine. Second, the control unit would sufficiently amplify the electrical impulses recorded on the tape to operate the three servomotors added to the machine to enable automated control of the machine’s X, Y and Z axes.

This magnetic-tape method was one of a few different approaches to NC developed by a handful of companies at that time. Ultimately, the industry settled on the punched-tape method. Regardless, machining parts without an operator manipulating handwheels had to be an “out-there” concept at the time. It is not surprising that the writer of one of the first articles about automatic machining referred to this new capability as both “mysterious and startling.” As it turns out, NC was one of the first major steps toward applying automation in a machine shop.

So, is this the most transformative machining process in more than 60 years? The natural transition from NC to computer numerical control (CNC) was certainly impactful, but that was simply an evolutionary step thanks to advancements in digital computer technology. When electrical discharge machining (EDM) arrived on the scene in the late 1970s, some pontificated that it would eventually replace conventional chip-making processes. That never happened, although EDM certainly is well suited for niche applications such as machining hard metals.

Today, some similarly say that additive manufacturing (AM) could possibly be a huge game changer in terms of discrete-parts production. Thus far, however, AM seems to be more of a complementary technology to CNC machining, not a replacement.

John T. Parsons is credited for being the “father of NC” thanks to his initial work to develop punched-tape automatic machining back in the 1940s. It is unknown when the next concept that will be as impactful as NC will be created. However, plan for Modern Machine Shop to be around to present it to our audience.