Automotive spot welding (GM and Ford volumes)

3,000 spot welds per automobile to get 2,000 good ones; nickel per weld → ~$150/car. GM ~50 billion spot welds per year. Aerospace combustor cans: ~$3/weld due to QC overhead.

There is a heat intensity that produces about 10⁵ watts per square centimeter, and that's resistance spot welding. Basically it's used in automobiles extensively for putting together steel sheet metal. Two pieces of galvanized steel, you put them together, you bring in two copper electrodes at about 10,000 psi pressure, you pass about 10,000 amps for about a third of a second, and you just melt the inside. You form a little button. The guy who invented this was Elihu Thomson, a professor of electrical engineering at MIT. He was president of MIT for one year. He started a company with a guy named Thomas Edison up here in Lynn, Massachusetts, called General Electric. Thomas Edison had about 400 patents, more than anybody else. Elihu Thomson had about 380 — he was number two in patents at the time, around the 1890s.