Automobile spot welding quality

Used to introduce resistance spot welding — Elihu Thomson, GE/MIT co-founder, ~1900. Tom's recurring "3,000 spot welds, 2,000 good ones" figure for automotive practice.

Have I told you the titanium electron beam welding at General Electric? No, okay. This is a similar type of problem. At the time, this was mid 80s, General Electric Lynn up here. They sort of abused me, actually. General Electric Lynn Aircraft Engines had wanted to improve the spot welding. This is where you use two big copper electrodes and you put two pieces of sheet metal between the two electrodes, and you pass 10,000 amps for a third of a second, and you can weld a little button between those two electrodes. It's called a resistance spot weld, invented by Elihu Thomson, who had been president of MIT. He was the co-founder of General Electric with Thomas Edison back around 1900. It's the way they weld all kinds of automobiles. I'm known for having said you need 3,000 spot welds in the average automobile because you need 2,000 good ones. When it's working well it's a very reliable, very fast process. It costs about a nickel to ten cents for every weld that goes in an automobile, because you're just bang — you're making 60 welds a minute on an assembly line, which is incredible. But that's why they get a thousand bad ones out of three thousand.

3,000 spot welds per car / 2,000 good ones; ~$0.05 per weld; aggregate worldwide volume ~90 billion welds per year (Tom's live arithmetic). Used to demonstrate that joining cost equals material cost in automotive bodies.

I could have predicted that. In "Defense and Industry Materials for the 21st Century," my little four- or five-page thing on material selection — the relative price of steel to aluminum is about two to one. So, duh. It's not hard to estimate these things. You say, well gee, it's only $500 more to buy that car. The problem that she didn't recognize in her thesis: she assumed that you could resistance spot weld aluminum just like you do steel. Remember I said it takes 3,000 spot welds in the average automobile, because you need 2,000 good ones. There are 50 to 100 billion spot welds made for automobile production in the world. If you build 30 million cars, and you've got 3,000 spot welds, that's 90 billion spot welds. Maybe it's a trillion spot welds. I had estimated that the spot welding in the average automobile was about a nickel per weld. So a nickel per weld times 3,000 welds — that's $150 for welding. The welding cost was equal to the material cost. If you go to that little handbook I gave you, the material cost of a car is about 10% of the cost of the car, the joining cost is about 10%, and the stamping and other costs may be 10%. How much of the stamping of the metal you buy — what's the buy-to-fly ratio for sheet metal of an automobile? It's about two to one. Half of it goes into scrap, because when you punch out those holes for the windows, that's scrap right out of that sheet metal.

Tom's example of a sound bite with content — used to illustrate the Thurow lesson. Quoted back to him by a stranger at a welding conference a year later. Likely connects to cluster "Automotive spot welding quality" but is delivered specifically as a *rhetorical-form* anecdote, not as a forensic teaching case.

About a year later, around 1990, I was at a conference and I had to give the keynote speech at some welding conference. I was talking about resistance spot welding, and I said: they put 3,000 spot welds in the average automobile because they need 2,000 good ones. I had a nice slide of that — it wasn't PowerPoint back then. A year later I'm at a welding conference, at the cocktail party, and I hear someone behind me say, "Did you know they put 3,000 spot welds in the average automobile because—" They're quoting the sound bite. If you can learn to speak in sound bites, you can be President of the United States. And you don't even have to have content to your sound bites. Mine actually had some content. It changed the way I gave talks, it changed the way I taught.