Boeing aluminum wing manufacturing waste

Reference to Boeing wings machined from plate, ~20:1 buy-to-fly ratio. Brief — back-reference to earlier lecture treatment.

When I talked about the Boeing wings, they start with plate and then machine away all the material they don't want, and the buy-to-fly ratio on that aluminum wing is probably something on the order of 20 to 1. There are some parts in aircraft engines and other parts — I've seen buy-to-fly ratios of 100 to 1. Well, not anymore. The Air Force spent billions of dollars in the '90s on what we call near net shape manufacturing, and we're going to talk about a little bit of near net shape today.

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80–90% of the heat-treated Alcoa plate is machined away as chips to produce the final wing structure with bosses and thinner sections. Used to motivate why welding is avoided (residual stresses) and machining is preferred despite the waste.

When they heat treat this six inches thick to get the strength, they get tremendous residual stresses. And when you start machining this — all the little cavities and everything — they may throw away 80, 90 percent of the weight of the aluminum after they take this solid chunk and turn it into a thinner section with all these bosses and stuff. You don't want to have to weld it; they machine the whole thing. They've got tons and tons of aluminum, they may throw away 80, 90 percent of the weight as machining chips. But it's got tremendous residual stresses, and if you don't get rid of them you're going to have fatigue problems.