I'm mostly interested in the manufacturing technology -- seems like they're doing some kind of friction/ultrasonic/diffusion welding between the titanium frame

I'm mostly interested in the manufacturing technology -- seems like they're doing some kind of friction/ultrasonic/diffusion welding between the titanium frame and the aluminium insides. That's a notoriously difficult weld to make: https://doi.org/10.1177/14644207211010839 https://doi.org/10.1177/14644207211010839 I would love to know what process they're using and how they've got it reliable!