What The Audi R8 And The New Ludicrously Thin iMac Have In CommonS

Apple announced a bunch of new products today, including a redesigned iMac that brings us a step closer to humanity's dream of a desktop computer thin enough to chop onions. The new iMac is aluminum, and traditional welding methods won't really work to join panels for such a thin (5mm thick) enclosure. To get around this, they're using a method known as Friction Stir Welding.

You know where else this exotic method is used? In cars. Cars like the Audi A8, Ford GT, and even more prosaic mounts like the Volvo V70 and Toyota Prius.

As Apple proudly says on their site:

The enclosure is so thin, it's not possible to weld the pieces using traditional methods. So we searched far and wide for other ideas, and we found one in a process called friction-stir welding. It's commonly used on airplane wings, rocket booster tanks, and other parts that simply can't fail. This process uses a combination of intense friction-generated heat and pressure to intermix the molecules of the two aluminum surfaces - creating a seamless, precise, and superstrong join. You may not see it, but the new iMac wouldn't be possible without it.

What The Audi R8 And The New Ludicrously Thin iMac Have In CommonS

The welding method itself is pretty fascinating. If you've ever done any welding, you'll know that melting the two metals to be joined is pretty key to the process, whether you're using arc or gas welding. Friction Stir welding doesn't melt the metal at all— it does soften from friction heat, but the two parts to be joined are mechanically mixed together. Stirred, as the name suggests. Essentially, a rotating tool nib spins on and slightly into the two materials right on the line where they abut. The friction of the nib on the material slightly plasticizes them from the heat, and the materials are mixed as the rotating tool advances down the join. The metal is heated a bit, but not melted, and the mixing occurs at a molecular level, leaving a strong, clean join. It's pretty cool.

On cars, those of you with access to a Ford GT should scrutinize the center tunnel for samples of a FSW join. If you're near an Audi R8 Spider, check the B-pillar, in the Prius, check the tack where the tailgate struts meet the gate. If you're not near a car, but you're near an Orion space capsule, check where the bulkhead meets the nosecone, or hop over to one of your Delta II or IV rockets and look at the interstage modules. Neat, huh?

I think the iMac will be the first mass-market indoor product use of FSW methods, so it'll be interesting to see if the method catches on for a larger range of more cheap, common items.

I do kind of miss the shower of sparks of regular arc welding, though.