Additive manufacturing methods could be addictive if they prove efficient
(Image credit: Apple)
Apple has adopted additive manufacturing (or 3D printing) for making chassis for Apple Watches as well as USB-C port receptacles for the ultra-thin iPhone Air. The company is printing these components using titanium powder obtained from recycling, thus greatly reducing usage of materials while achieving its products' signature great looks and structural strength. This is the first time that Apple has applied additive manufacturing for a mass-market device.
To build chassis for Apple Watch Ultra 3, Apple Watch 11 titanium, and the USB-C receptacle of the iPhone Air, Apple uses a special powder-based laser process that fuses together fine titanium grains — each around 50 micrometers across and refined to keep oxygen levels low to avoid explosions during heating — layer by layer using a laser. To produce one watch chassis, the company says a metal 3D printer with one galvanometer housing six lasers makes 900 passes to craft numerous layers that are exactly 60 microns thick.
Once the printing run completes, the partially buried components must be cleaned and separated. Excess powder is first vacuumed away, then removed from pockets and channels using an ultrasonic shaker. Individual chassis are then freed from the build block by a thin wire that slices between them, while a coolant jet keeps temperatures low to prevent distortion. Finally, optical metrology checks dimensions and appearance to ensure the pieces meet the strict visual and structural tolerances required before they reach the assembly line.
Apple says that usage of this titanium powder-based 3D printing method allows it to cut titanium usage in half compared to earlier machining-based production methods, or by over 400 metric tons of raw metal in a single year.
Lots of companies use similar metal 3D-printing methods for titanium or other metals, but almost no company has done it at Apple's scale of millions of parts. The company says that adopting this technology required years of trial builds, material experiments, and validation runs. Apple also had to refine its titanium alloy recipe, calibrate the printing parameters, and ensure that surfaces produced this way match those made using forging and machining,
One advantage unlocked by this method is the ability to form intricate surfaces that traditional forging cannot reach. For the cellular versions of the watch, a textured interior pattern can now be printed directly into sections that interface with plastic components to enhance the seal and improve radio performance thanks to stronger bonding between metal and polymer.
Apple stresses that two Apple Watch chassis and the USB-C frame used in the iPhone Air are just the beginning for its use of additive manufacturing. The company sees more possibilities for 3D printing far beyond these first products, but it stresses that further adoption of the technology will require it to rethink how its future devices are designed and built.
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Anton Shilov is a contributing writer at Tom’s Hardware. Over the past couple of decades, he has covered everything from CPUs and GPUs to supercomputers and from modern process technologies and latest fab tools to high-tech industry trends.
I'd like to see that backed up with a full supply chain analysis. Machined bulk materials are relatively trivial to recycle: keep the swarf separated, clean it of cutting fluid, and it's ready to go back to the foundry, or even be melted and recast directly for some alloys.
But for 3D printing, the powders are not as easy to handle. You might be able to get away with re-using already cycled powder one or two times, but that comes with a compromise in quality: the powders oxidise very rapidly once the delivery container is unsealed which affects metallurgy and beam melting behaviour (albedo change, enthalpy change, chemical change, etc), and beam spill produced partially sintered multi-particle 'clumps' that are worthless for use (result in voids) so need to be filtered out, which is easier said than done for metallic powders that have awkward flow characteristics and already love to clump without agitation (why powder spreaders in metallic particle bed fusion machines are so finicky). That means recycling the unused powder is far more of a challenge than recycling metallic swarf, with a far greater energy input needed to get that oxidised powder back to useable metal.
The basic "raw stock in / finished part out" mass percentage may be better than bulk machining, but I doubt it's an improvement once you stop ignoring the rest of the recycling and reuse process.
