Oh, CNC of course. Subtractive milling though, not glue gun additive.
Here's Andy Payne (bloke who wrote CamBam) demoing his take on the idea, after we muttered "cycloidal drive" at him and he wrote the code to generate the magic curves for drawing the lobulators.
Not that they ever did, nor had a hope in hell of doing anything like that. By the time the ZX81 came out some UK power stations were already using real time boiler control with DEC PDP 11's
A BBC did get used at one UK power station in the 80's but be buggered if I can remember precisely what it did.
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