Although I've read about it, I hadn't had a chance to touch the all-in-one machined SRAM cassette until last weekend. This thing is machined from a solid block of material. Although, they could possibly have the raw material cast to near-net shape (a truncated cone) so they have less to remove.I'm guessing that the part is first turned on a CNC lathe that hollows the inside and cuts the grooves between the cogs on the outside. A CNC mill then machines the tooth profiles, shifting ramps and freehub splines. Finally, an anodized cap is put on the bottom so that the cassette can be centered and mounted on a hub. Maybe this is all done in a multi-axis turning/milling center. The question is - will this manufacturing technique be refined to the point it can be cheap enough to make lower end gear sets this way? For the forseable future, individual stamped cogs and hand assembly in lower cost countries will continue to be the way cassettes are made.
It was great, however, of SRAM to cross section one for our inspection.