Unibody enclosures
Adam Banks remembers when Jonathan Ive made laptops thinner by taking out their bones
Steve Jobs took to the stage at San Francisco’s Moscone Center in January 2008, home to that year’s Macworld Expo, to introduce the MacBook Air, “the world’s thinnest notebook” – thinner at its thickest point, in fact, than Sony’s rival laptop design was at its thinnest.
Later that year, at Infinite Loop’s Town Hall, design chief Jonathan Ive made a rare public appearance to explain how it was possible. He showed the structure of an earlier MacBook, with an aluminium skin (other makers used plastic) welded over a complicated frame assembled from multiple parts: “Whenever you have multiple parts, you add size and weight,” he explained. But it was essential to make the case “strong, robust, torsionally rigid” – an issue familiar to computer reviewers, who begin any assessment of a clamshell machine by opening it up and attempting to twist each half. “We decided just to start over,” said Ive.
The MacBook Air’s chassis – now reproduced for the MacBook Pro – was completely different. Rigidity came not from a frame under a thin skin, but a thicker skin with the structure built in. Apple’s description for this design was “unibody”, a term used in the automobile industry since the Second World War, but never before in the field of portable computers.
Advanced manufacturing techniques, including CNC (Computer Numerical Control) machining and laser piercing, were combined to cut a single piece of aluminium into the highly complex and incredibly precise shape required. This meant shaving off all but 113g of a 1.135kg aluminium slab, and one of the innovations that made the method feasible at all was the ability to recycle the waste metal.
The following year’s iMac was also unibody, and by 2012 it was possible to slim the case as dramatically as with the MacBook Air. A memory hatch on the 27-inch model, however, acknowledged the downside: an unbroken surface meant the chances of disassembling the device without a good deal of difficulty were slim.