automated manufacturing

2 Articles

Retrotechtacular: The Tyranny Of Large Numbers

January 30, 2025 by 3 Comments

Although much diminished now, the public switched telephone network was one of the largest machines ever constructed. To make good on its promise of instant communication across town or around the world, the network had to reach into every home and business, snake along poles to thousands of central offices, and hum through the ether on microwave links. In its heyday it was almost unfathomably complex, with calls potentially passing through thousands of electronic components, any of which failing could present anything from a minor annoyance to a matter of life or death.

The brief but very interesting film below deals with “The Tyranny of Large Numbers.” Produced sometime in the 1960s by Western Electric, the manufacturing arm of the Bell System, it takes a detailed look at the problems caused by scaling up systems. As an example, it focuses on the humble carbon film resistor, a component used by the millions in various pieces of telco gear. Getting the manufacturing of these simple but critical components right apparently took a lot of effort. Initially made by hand, a tedious and error-prone process briefly covered in the film, Western Electric looked for ways to scale up production significantly while simultaneously increasing quality.

While the equipment used by the Western engineers to automate the production of resistors, especially the Librascope LGP-30 computer that’s running the show, may look quaint, there’s a lot about the process that’s still used to this day. Vibratory bowl feeders for the ceramic cores, carbon deposition by hot methane, and an early version of a SCARA arm to sputter gold terminals on the core could all be used to produce precision resistors today. Even cutting the helical groove to trim the resistance is similar, although today it’s done with a laser instead of a grinding wheel. There are differences, of course; we doubt current resistor manufacturers look for leaks in the outer coating by submerging them in water and watching for bubbles, but that’s how they did it in the 60s.

The productivity results were impressive. Just replacing the silver paint used for terminal cups with sputtered gold terminals cut 16 hours of curing time out of the process. The overall throughput increased to 1,200 pieces per hour, an impressive number for such high-reliability precision components, some of which we’d wager were still in service well into the early 2000s. Most of them are likely long gone, but the shadows cast by these automated manufacturing processes stretch into our time, and probably far beyond.

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Printed Circuits, 1940s Style

December 8, 2020 by 35 Comments

A presentation this month by the Antique Wireless Museum brought British engineer and inventor John Sargrove (1906-1974) to our attention. If you’ve ever peeked inside old electronics from days gone by, you’ve no doubt seen point-to-point wiring and turret board construction. In the 60s and 70s these techniques eventually made way for printed circuit boards which we still use today. But Mr Sargrove was way ahead of his time, having already invented a process in the 1930s to print circuits, not just boards, onto Bakelite. After being interrupted by the war, he formed a company Electronic Circuit Making Equipment (ECME) and was building broadcast radio receivers on an impressive automatic production line.

Mr. Sargrove’s passion was making radios affordable for everyone. But to achieve this goal, he had to make large advances manufacturing technology. His technique of embedding not only circuit traces, but basic circuit elements like resistors, capacitors, and inductors directly into the substrate foresaw techniques being applied decades later in integrated circuit design.  He also developed a compact vacuum tube which could be used in all circuits of a radio, called an “All-stage Valve“. Equally important was his futuristic automatic factory, which significantly reduced the number of factory workers needed to make radios from 1500 to 50. Having completed the radio design, he was also developing a television receiver using the same concepts. Unfortunately, ECME was forced into liquidation when a large order from India was cancelled upon declaration of independence in 1947.

You really must watch the video below. There are many bits and pieces of modern factory automation which we still use today, yet their implementation using 1940s techniques and technology is fascinating. Further reading links after the video. Thanks to [Mark Erdle] for the tip.

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